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Originally appearing in Volume V20, Page 497 of the 1911 Encyclopedia Britannica.
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PART III.-THE TECHNIQUE OF PAINTING § 29. The Materials of Painting.--Painting begins, as we have seen, on the one side in outline delineation, on the other in the spreading of a coating of colour on a surface. For both these the material apparatus is ready at hand.- Drawing may have begun merely with lines in the air, but lasting designs were soon produced either by indenting or marking any soft substance by a hard point, or by rubbing away a comparatively soft substance, such as a pointed piece of burnt wood, on a rough surface of harder grain. Almost all the materials in use for drawing are of primitive origin. Charcoal, coloured earths and soft stones are natural or easily procured. Our plumbago was known to Pliny (xxxiv. 18) and to Cennino (ch. 34), but it was not in common use till modern times. The black-lead pencil is first described as a novelty in 1565 (Quellenschriften edition of Cemmno, p. 143). A metal point,of ordinary lead or tin was used in medieval MSS. for drawing lines on parchment, or on a wooden surface previously whitened with chalk (Theophilus, II. ch. xvii.). Silver-point drawing is only a refinement on this. The metal point is dragged over a surface of wood or parchment that has been grounded with finely powdered bone-dust, or, as in modern times, with a wash of Chinese white (Cennino, ch. 6 seq.; Church, 292), and through the actual abrasion of the metal leaves a dark line in its track. Pliny knows the technique (xxxiii. 98). When a coloured fluid was at hand a pointed stick might be used to draw lines with it, but a primitive pen would soon be made from a split reed or the wing-feather of a bird. The coating of one substance by another of which the colour is regarded from the aesthetic standpoint is the second source of the art of painting. To manipulate the coating substance so that it will lie evenly; to spread it by suitable mechanical means; and to secure its continued adherence when duly laid, are by no means difficult. Nature provides coloured juices of vegetable or of animal origin, and it has been suggested that the blood of the slain quarry or foeman smeared by the victor over his person was the first pigment. To imitate these by mixing powdered earths or other tinted substances in water is a very simple process. Certain reeds, the fibres of which spread out in water, were used as paint-brushes in ancient Egypt. A natural hare's-foot is still employed in theatrical circles to lay on a certain kind of pigment, and no great ingenuity would be required on the part of the hunter for the manufacture of a brush from the hair or bristles of the slain beast. In the matter of securing the adhesion of the coating thus spread, nature would again be the guide. Many animal and vegetable products are sticky and ultimately dry hard, while heat or moisture thins them to convenient fluidity. Great heat makes mineral substances liquid that harden when cold. Hence binding materials offer themselves in considerable abundance, and they are of so great importance in the painter's art that they form the basis of current classifications of the different kinds of painting. § 30. The Surfaces covered by the Painter.—Many important questions connected with the technique of painting depend on the nature of surfaces; for the covering coat—though from the present point of view only of interest aesthetically—may, as we have seen, originally serve a utilitarian purpose. The surface in question may be classed as follows: the human body; implements, vessels, weapons, articles of dress; objects of furniture, including books; boats and ships; walls and other parts of buildings; panels and other surfaces prepared especially or entirely to be painted on. The differences among these from the present point of view are obvious. The body could not suitably be covered with a substance impervious to air and moisture; the coatings of a clay vessel and of a boat should on the other hand make them waterproof. The materials used in building often require protection from the weather. The painting on the prepared panel needs to resist time and any special influence due to location or climate. All such considerations are prior to the questions of colour, design, or aesthetic effect generally, in thesecoatings; and on them depend the binding materials, or media, with which the colouring substances are applied. The case of one particular surface much employed for pictorial display is exceptional. This is the wall-plaster so abundantly used for clothing an unsightly, rough, or perishable building material, like rubble or crude brick. This function it performs perfectly when left of its natural white or greyish hue, but its plain unbroken surface has seemed to demand some relief through colouring or a pattern, and the recognition of this led to one of the most important branches of the art, mural painting. Now lime-plaster, if painted on while it is still wet, retains upon its surface after it has dried the pigments used, although these have not been mixed with any binding material. On all other surfaces the pigments are mixed with some binding material, and on the character of this the kind of painting depends. There is thus a primary distinction between the process just referred to and all others. In the former, pigments, mixed only with water, are laid on while the plaster is wet, and from this " freshness " of the ground the process is called by an Italian term, painting " a fresco " or " on the fresh," though in ordinary parlance the word " fresco" has come to be used as a noun, as when we speak of the " frescoes " of Giotto. Furthermore, as " fresco " is the wall-painter's process par excellence the word is unfortunately often employed inaccurately for any mural picture, though this may have been executed by quite a different process. In contradistinction to painting " a fresco " all other processes are properly described by the Italian term " a tempera," meaning " with a mixture." The word is used as a noun in the sense of a substance mixed with another; but it is to be regarded as the imperative of the verb temperare, which both in Latin and Italian means " to divide or proportion duly," " to qualify by mixing," and generally " to regulate." Tempera means strictly " mix," just as " recipe," also employed as a substantive, is an imperative meaning "take." In ordinary parlance, however, the word tempera is confined to a certain class of binding materials to the exclusion of others, so that the more general term " media " is the best to employ in the present connexion, We go on, therefore, to consider these various media in relation to different surfaces and conditions. § 31. Binding Materials or Media.—The fundamental distinction among media is their solubility or non-solubility in water, though, as will be seen presently, some possess both these qualities. The non-soluble media are (i) of mineral, (2) of vegetable origin. (i) Of the former kind are all vitreous pastes or pottery glazes, with which imperishable coloured surfaces or designs are produced on glazed tiles used in the decoration of buildings, on ceramic products, and in all processes of enamelling. Silicate of potash, employed to fix pigments on to mural surfaces of plaster in the so-called " stereochrome " or " water-glass " processes of wall paintini (see § 37), is another mineral medium, so too is paraffin wax. In the process called (unscientifically) " fresco secco," in which the painting is on -dry plaster, lime is used as a binding material for the colours. Its action here is a chemical one (see § 36). (2) Non-soluble vegetable media are drying oils, resins, waxes (including paraffin wax, which is really mineral). In ancient times wax, and to some small extent also resins, were used as a protection against moisture, as in shipbuilding and some forms of wall-painting. Resins have always remained, but wax gradually went out of use in the earlier Christian centuries, and was replaced by the new medium, not used in classical times, of drying oil. In northern lands the desire to protect painted surfaces from the moisture of the air led to a more extensive use of oils and resins than in Italy; and it was in the Netherlands that in the 15th century oil media were for the first time adopted in the regular practice of painting, which they have dominated ever since. The soluble media are of animal and vegetable origin. Egg, yolk or white, or both combined, is the chief of the former. Next in importance are size, gained by boiling down shreds of parchment, and fish glue. Egg is the chief medium in what is specially known as " tempera " painting, while for the painting commonly called distemper or "gouache," of which scene-painting is typical, size is used. Milk, ox-gall, casein and other substances are also employed. Of soluble vegetable media the most used are gums of various kinds. These are common " temperas " or tempera media, and, with glycerin or honey, form the usual binding material in what is called " water-colour " painting. Wine, vinegar, the milk of fig-shoots, &c., also occur in old recipes. Attention must be drawn to the fact that substances can be prepared for use in painting that unite soluble and insoluble media, but can be diluted with water. These substances are known as " emulsions." A wax emulsion, which is also called " saponified wax," can be made by boiling wax in a solution of potash [in the proportions too bleached wax, ro potash, 250 distilled water (Berger, Beitr¢ge, i. roo)] till the wax is melted. When the solution has cooled it can be diluted with cold water. An admixture of oil is also possible. This, according to Berger, is what Pliny and-Vitruvius (vii. 9, 3) call " Punic wax," a material of importance in ancient painting. An oil emulsion can be made by mixing drying oil with water through .the intermediary of gum or yolk of egg. An intimate mechanical compound, not a chemical one, is thus effected, and the mixture can be diluted with water. If gum arabic be used the result is a " lean " emulsion of a milky-white colour, if yolk of egg a " fat " emulsion of a yellowish tint. When these wax or oil emulsions are dry they have the waterproof character of their non-soluble constituents. Lastly, it must be noticed that certain substances used in the graphic arts—some of which possess in themselves a certain unctuousness—can be, as it were, rubbed into a suitably roughened, and at the same time yielding, ground, to which they will adhere, though loosely, without binding material. This is the case with charcoal, chalks and pencil. The same property is imparted by a little gum or starch to soft coloured chalks, with which is executed the kind of work called " pastel." These are now also made up with an oleaginous medium and are known as " oil pastels." Pictures can be carried out in ordinary or in oil pastels, and the work should rank as a kind of painting. The coloured films, rubbed off from the sticks of soft chalk on a suitably rough and sometimes tinted paper, are artistic in their texture and capable of producing very beautiful effects of colour. Professor Church notes also that the colours laid on in this fashion seem peculiarly durable (Chemistry, p. 293). § 32. The Processes of Painting: Preliminary Note.—These will be discussed from the point of view of the media employed, but certain departures from strict logical arrangement will be convenient. Thus, different processes of monumental painting on walls may be brought together though distinct media are employed. Tempera and early oil practice cannot be separated. Painting by the use of vitreous glazes fused by heat may be noticed first, as the process comes within the scope of the article, though it. has generally been applied in a purely decorative spirit, so as to be a branch of the art of ornament rather than strictly speaking of painting (see § 2). In painting processes proper fresco takes the lead. It is in its theory the simplest of all, and at the same time it has produced some of the most splendid results recorded in the annals of the art. With the fresco process may be grouped for the sake of convenience other methods of wall-painting, which share with it at any rate some of its characteristics. One of these subsidiary methods of wall-painting is that known as the wax process or " encaustic," used in ancient times and revived in our own. Painting in wax, not specially on walls, was an important technique among the ancient Greeks, and the consideration of it introduces some difficult archaeological questions, at which space will not allow more than a glance. The wax used in the process, softened or melted by heat or driven by fire into the painting ground—whence the name "encaustic " or " burning in "—is really a tempera or binding material, and we are brought here to the important subject of tempera painting in general. It will have to be noticed in this connexion what were the chief binding materials used in the so-namedtechnique in different lands at the various stages of the art, and what conditions were imposed on the artist by the nature of his materials. Lastly, there is the all-important process in which the binding materials are oils and varnishes, a process to which attaches so much historical and artistic interest, while a form of tempera painting that has been specially developed in modern times, that known as water-colour, may claim a concluding word. § 33- Historical Use of the Various Processes of Painting.—The extent and nature of the employment of these processes at different periods may have here a brief notice. Tempera painting has had a far longer history and more extended use than any other. The Spaniard Pacheco, the father-in-law and teacher of Velazquez, remarks on the veneration due to tempera because it had its birthday with art itself, and was the process in which the famous ancient artists accomplished such marvels. In the matter of antiquity, painting with vitreous glazes is its only rival: glazed tiles formed, in fact, the chief polychrome decoration for the exteriors of the palaces of Mesopotamia, and were used also in Egypt; but all the wall-paintings in ancient Egypt and Babylonia and Mycenaean Greece, all the mummy cases and papyrus rolls in the first-named country are executed in tempera, and the same is true of the wall-paintings in Italian tombs. In Greece Proper paintings on terra-cotta fixed by fire were very common in the period before the Persian wars. When monumental wall-painting came to the front just after that event it was almost certainly in tempera rather than in fresco that Polygnotus and his companions executed their masterpieces. It has been doubted whether these artists painted directly on plaster or on wooden panels fixed to the wall, but the discovery in Greece of genuine mural paintings of the Mycenaean period has set these doubts at rest. In Italy tomb-paintings actually on plaster exist from the 6th century B.C. The earlier panel painters of the 5th and 4th centuries B.C. also used tempera processes, though their exact media are not recorded. About the time of Alexander there seems to have been felt a demand for a style of painting in which could be obtained greater depth and brilliancy of colouring, with corresponding force in relief, than was possible in the traditional tempera; and this led to painting in a wax medium with which abundance of " body " could be secured. There are many puzzling questions connected with this ancient encaustic, but the discovery in recent years of actual specimens of the work, in the form of portraits on the late Egyptian mummy cases of the first centuries A.D. have assisted the study. Meanwhile a new technique to have been in process of evolution for use on walls, for the fresco process, in a complete or modified form, was certainly in use among the Romans. The history of the fresco process, as will presently be seen, is somewhat puzzling. Vitruvius and Pliny knew it, and it is mentioned in the Mount Athos Handbook, which incorporates the technical traditions of the art of the Eastern Empire; it appears also to have been in use in the Christian catacombs, but was not practised by the wall painters who adorned the early medieval churches south and north of the Alps. The difficulties of the process, and another reason to be noticed directly, may have led to its partial disuse in the West, but we find it again coming into vogue in Italy in the 13th and 14th centuries. In the early Christian centuries its place was taken in the monumental decoration of walls by marble inlays, and especially by glass mosaic, which is in itself an important form of wall-painting and may have put painting on plaster, and with it the fresco process, into the shade; notice will however presently be taken of a theory that seeks to establish a close technical connexion between mosaic work and the fresco painting, which, on the decline in the later medieval period of mosaic, came forward again into prominence. The tempera processes were accordingly in vogue in early medieval times for wall-paintings (except to some extent in the East), for portable panels, and on parchment for the decoration and illustration of manuscripts. Meanwhile the use of drying oils as painting media was coming to be known, and both on plaster and on wood these were to some extent employed through the later medieval period, though without seriously challenging the supremacy of tempera. From the beginning of the 15th century, however, oil painting rose rapidly in estimation, and from the end of that century to our own time it has practically dominated the art. Wall-painting in fresco continued to be practised till the last part of the 18th century, and has been revived and supplemented by various other monumental processes in the 19th, but even for mural work the oil medium has proved itself a convenient substitute. Water-colour painting in its present form is essentially an art of the last hundred years. The old tempera processes have been partly revived in our own time for picture-painting, but the chief modern use of tempera is in scene-painting, where it is more commonly called " distemper." § 34. Painting with Coloured Vitreous Pastes.—There is no single work that deals with the whole subject of this material and its different uses in transparent or opaque form in the arts, but details will be found in the special articles where these uses are described. (See CERAMICS; MOSAIC; ENAMEL; GLASS, STAINED.) On the subject of the substances and processes employed in the colouring of the various vitreous pastes information will be found in H. H. Cunynghame's Art Enamelling on Metals (2nd ed., London, 1906, ch. vi.), but the subject is a large and highly technical one. Coloured vitreous pastes are among the most valuable materials at the command of the decorative artists, and are employed in numerous techniques, as for example for the glazes of ceramic products including wall or floor tiles; for painted glass windows; for glass mosaic, and for all kinds of work in enamels. The vitreous paste is tinged in the mass with various metallic oxides, one of the finest colours being a ruby red obtained from gold. Silver gives yellow, copper a blue green, cobalt blue, chromium green, nickel brown, manganese violet, and so on. Tin in any form has the curious property of making the vitreous paste opaque. It should be understood that though the vitreous substance and the metallic oxides are essentially the same in all these processes, yet the preparation of the coloured pastes has to be specially conditioned in accordance with the particular technique in view. There are generally various ways of producing reds and blues and greens, &c., from oxides of different metals. The material is generally lustrous, and it admits of a great variety in colours, some of which are highly saturated and beautiful. It is on the lustre and colour of the substance, rather than on the pictorial designs that can be produced by its aid, that its artistic value depends; but though this implies that it comes under the heading " Ornament " rather than " Painting," yet in certain forms and at particular periods it has been the chief medium for the production of pictorial results, and must accordingly have here a brief notice. . The difference between opaque and transparent coloured glass is the basis of a division among the arts that employ the material. If it be kept transparent the finest possible effect is obtained in the stained-glass window, where the colours are seen by transmitted light. The stained-glass window came into general use in the early Gothic period, and was a substitute for the wall-paintings which had been common in the Romanesque churches of the r rth and 12th centuries. Hence it is a form, and a very sumptuous and beautiful form, of the art of mural painting, representing that art in the later medieval buildings north of the Alps. In Italy, where the practice of wall-painting continued without a break from early medieval to Renaissance times, the stained-glass window was not a national form of art. The most effective use of opaque coloured vitreous pastes is in ceramics (pottery) and in glass mosaic. The terra-cotta plaque, or tile-painted with designs in glazes of the kind was, as we have seen (§ 7), one of the chief forms of exterior mural decoration in ancient Mesopotamia. The best existing examples were found not long ago on the site of the ancient Susa (" Shushan the palace " of Scripture) and are now in the Louvre. Human figures, animals, and ornaments, are represented not only in lively colours but also in relief; that is to say, each separate glaze brick had its surface, measuring about 12 in. by 9 in., modelled as well as painted for the exact place it had to occupy in the design. On these bricks there are formed small ridges in relief intended to keep the different liquid glazes apart before they were fixed by vitrifaction in the kiln. Chemical analysis has shown that the yellow colour is an antimoniat of lead, the white is oxide of tin, similar to the well-known opaque white glaze used by the Della Robbia in Italy, the blues and greens are probably oxides of copper, the red a sub-oxide of copper (Semper, Der Stil, 332). This same region of the world has remained through all time a great centre for the production of coloured glazed tiles, but the use of " Persian," " Moresque," and other decorated plaques has been more ornamental than pictorial. Glazed pottery only comes occasionally within the survey of the historian of painting. It does so in ancient Greece, because the earlier stages of the development of Greek painting can only be followed in this material; it does so, too, in a sense, in Italian faience and in some Oriental products, but these hardly fall within our view. The Greek vase was covered with a black glaze of extreme thinness and hardness, the composition of which is not known. Figure designs were painted in this on the natural clay of the vessel (see fig. 3, Plate IV.), or it was used for a background, the design being left the colour of the clay. Other colours, especially a red (oxide of iron) and white, were also employed to diversify the design and emphasize details, and these were also fixed by firing. A special kind of Greek vase was the so-called " polychrome lekuthos," a small upright vessel, the clay of which was covered with a white " slip " on which 'figure designs were painted in lively tints. The technique is not quite understood, but the colours were certainly fired. There is an article on " The Technical History of White Lecythi " in the American Journal of Archaeology for 1907; the processes are ne , however, analysed. In glass mosaic thin solid slabs of coloured vitreous pastes are broken up into little cubes of 4 in. to z in. in size and set in some suitable cement. The artist works from a coloured drawing and selects his cubes accordingly. Any number of shades of all hues can be obtained, and the modern mosaic workers of Italy boast that they dispose of some 25,000 different tints. As it is of the essence of the work to be simple and monumental in effect, a limited palette is all that is needed; and the mosaics recently executed in St Paul's in London are done in about thirty colours. The worker should have at hand appliances to cut to shape any particular cube wanted for a special detail. The ancients used the art, and the finest existing ancient picture is in a mosaic, not indeed of glass pastes, but of coloured marbles. This is the famous " Battle of Issus " found at Pompeii. Glass mosaic came in under the early Roman Empire, but its chief use was in early Christian times, when it was the chief material for mural decoration of a pictorial kind. Ravenna is the place where this form of painting is most instructively represented, and the 5th and 6th centuries A.D. are the times of its greatest glory. At Rome and Constantinople there is fine early work, while that at Venice and Palermo is later. In the earliest and best examples the design is very simple, and a few monumental forms of epic dignity, against a flat background commonly of dark blue, represents the persons and scenes of the sacred narratives. The effect of colour is always sumptuous. Gold, especially for the backgrounds, is in later work freely employed. The subject of enamel work forms the theme of a separate article. Here it need only be said that pictures can be produced by painting on a ground, generally of metal, with coloured vitreous pastes that are afterwards fixed by fusing. Limoges in France has been the great centre of the art, but enamelling loses in artistic value when a too exclusively pictorial result is aimed at. § 35• Fresco Painting.—Vitruvius (De Architectura, bk. vii. chs. 2, 3; age of Augustus), Mount Athos Handbook (Hermeneia, chs. 54 seq.; date uncertain but based on early tradition); Cennino Cennini (Trattato della pittura, chs. 67 seq., ed. Milanesi, 1859; Eng. trans. by Christiana J. Herringham, Lond., 1899); Leon Battista Alberti (De re aedificatoria, bk. vi. ch. 9; early and middle 15th century); Vasari (Opere, ed. Milanesi, i. 181; middle of 16th century)—all refer in general terms to the fresco process, as one generally understood in their times. Armenini (Dei veri precetti della pittura; Ravenna, 1587), and Palomino (El Museo pictorico; Madrid, 1715-1724), give more detailed accounts of the actual technical procedure, of which they had preserved the tradition. Much information of the highest value and interest was collected at the time when, in the forties of the 19th century, the project for the decoration in fresco of the new English Houses of Parliament was under discussion. This is contained in various communications by Sir Charles Eastlake, Mr Charles Heath Wilson, and others, printed with the successive Reports of the Commissioners on the Fine Arts from 1842 onwards. The experience obtained in the revived modern work in fresco by Cornelius, Hess, and other German artists encouraged by King Ludwig I. of Bavaria, which began at Rome in the second decade of the 19th century, was also drawn upon for the purpose of these Reports. A useful compendium was issued at the time by W. B. Sarsfield Taylor, A Manual of Fresco and Encaustic Painting (Lond., 1843). F. G. Cremer'sVollstdndige Anleitung zur Fresco-Malerei (Dusseldorf, 1891), may also be mentioned as a recent manual. The chemistry of the process is well explained by Professor Church in his Chemistry of Paints and Paintings. The fresco process is generally regarded as a method for the production of a picture. It is better to look upon it in the first place as a colour-finish to plaster-work. What it produces is a coloured surface of a certain quality of texture and a high degree of permanence, and it is a secondary matter that this coloured surface may be so diversified as to result in a pattern or a picture. We do not know among what people the discovery was first made that a wash of liquid pigment over a freshly laid surface of lime plaster remained permanently incorporated with it when all was dry, and added to it great beauty of colour and texture. The Egyptians, the Assyrians, the Phoenicians, the Mycenaean and later Greeks, the ancient Italians—all made extensive use of plaster as a coating to brickwork or masonry, but when they coloured it this was done after it was dry and with the use of some binding material or tempera. The earliest notice of the fresco technique that we have in extant literature is contained in the third chapter of the seventh book of Vitruvius, and it is there treated as a familiar, well-understood procedure, the last stage in the construction and finish of a wall. Pliny also in several passages of his Natural History treats the technique as a matter of common knowledge. In Vitruvius the processes of plastering albaria opera are first described (vii. 2, 3), and it is provided that after the rough cast, trullissatio, there are to follow three coats of plaster made of lime and sand, each one laid on when the one below is beginning to dry, and then three of plaster in which the place of the sand is taken by marble dust, at first coarse, then finer, and in the uppermost coat of all in finest powder. It might now be (1) finished with a plain face, but one brought up to such an exquisite surface that it would shine like a mirror (chs. 3, 9); or (2) with stamped ornaments in relief or figure designs modelled up by hand; or (3) it might be completed with a coat of colour, and this would be applied by the fresco process, for which Pliny uses the formula udo illinere, " to paint upon the wet." The reason why the pigments mixed with water only, without any gum or binding material, adhere when dry to the plaster is a chemical one. It was first clearly formulated by Otto Donner von Richter in connexion with researches he made on the Pompeian wall-paintings and published in 1868 as an appendix to Helbig's Campanische Wandgemalde. He demonstrated that when limestone is burnt into lime all the carbonic acid is driven out of it. When this lime is " slaked " by being drenched with water it drinks this in greedily and the resultant paste becomes saturated with an aqueous solution of hydrate of lime. When this paste is mixed with sand or marble dust and laid on to the wall in the form of plaster this hydrate of lime in solution rises to the surface, and when the wet pigment is applied to this the liquid hydrate of lime or lime water, to use Professor Church's phrasing, " diffuses into the paint, soaks it through and through, and gradually takes up carbonic acid from the air, thus producing carbonate of lime, which acts as the binding material " (Church, p. 278). It is a mistake to speak of the pigment " sinking into the wet plaster." It remains as a fact upon the surface, but it is fixed there in a sort of crystalline skin of carbonate of lime—the element originally banished when the lime was burned—that has now re-formed on the surface of the plaster. This crystalline skin gives a certain metallic lustre to the surface of a fresco painting, and is sufficient to protect the colours from the action of external moisture, though on the other hand there are many causes chemical and physical that may contribute to their decay. If, however, proper care has been taken through-out, and conditions remain favourable, the fresco painting is quite permanent, and as Vitruvius says (vii. 3, 7), " the colours, when they have been carefully laid upon the wet plaster, do not lose their lustre but remain as they are in perpetuity . . . so that a plaster surface that has been properly finished does not become rough through time, nor can the colours be rubbed off, that is unless they have been carelessly applied or on a surface that has lost its moisture." In the passage from which these words are taken Vitruvius gives useful hints as to the aesthetics of the fresco technique. Italian writers on the subject, such as Vasari, are generally so taken up with the pictorial design represented on the wall that the more essential characteristics of the process in itself are lost sight of. To Vitruvius the work is coloured plaster, not a picture on plaster, and he shows how important it is that the plaster should be finished with a fine surface of gleaming white so as to light up the transparent film of colour that clothes it. It is the result of such care in classical times that a surface of Pompeian plastering, self-tinted " a fresco," is beautiful without there being any question of pattern or design. This beauty and polish of Pompeian, and generally of ancient Roman plaster, has recently been made the ground for calling in question the view accepted for a generation past that it was merely lime plaster painted on " a fresco," and for substituting a totally different technical hypothesis. The reference is to the treatment of ancient wall-painting generally in the first part of Berger's Beitrage (2nd ed., 1904, pp. 58 seq.). This writer denies that the well-known classical wall-paintings in question are frescoes, and evolves with great ingenuity a wholly new theory of this branch of ancient technique. It is his view that the plaster was prepared by a special process in which wax largely figured and which corresponds to, and indeed survives in, the so-called " stucco-lustro " of the modern Italians. The process in question is described by_ L. B. Alberti (De re aedifcatoria, vi. 9), who says that when te plaster wall surface has been carefully smoothed it must be anointed with a mixture of wax, resin and oil, which is to be driven in by heat, and then polished till the surface shines like a mirror. This is a classical process referred to by Vitruvius under the name " ganosis," as applied to the nude parts of marble statues, possibly to tone down the cold whiteness of the material. Now Vitruvius, and Pliny, who probably follows him, do as a fact prescribe this same process for use on plaster, but only in the one special case of a wall painted " a fresco " with vermilion, which was not supposed to resist the action of the light unless " locked up," in this way with a coating of this " Punic " or saponified wax. Neither writer gives any hint that the process was applied to plaster surfaces generally, or that the lustre of these was dependent on a wax polish, and Vitruvius's description is so clear that if wax had been in use he would certainly have said so. Vitruvius prescribes so many successive coats of plaster, each one put on before the last was dry, and on the wet uppermost coat the colouring is laid. How can we with any reason substitute for this a method in which the plaster has to be made quite dry and then treated with quite a different material and process? Furthermore, Berger holds the astonishing theory that on the self-coloured surfaces of Pompeian and Roman plastered walls the colour was not applied, as in the fresco process, to the surface of the final coat, but was mixed up with the actual material of the intonaco so that this was a coat of coloured plaster. This is of course a matter susceptible of ocular proof, but the actual fragments of ancient coloured stucco referred to by Berger afford a very slender support to the hypothesis, whereas everyone who, like the present writer, possesses such fragments can satisfy himself that in almost 'every case the colour coat is confined to the surface. The writer has a fragment of such stucco from Rome, coloured with vermilion, and here there is clear evidence that some substance has soaked into the plaster to the depth of an eighth of an inch, as would be the case in the " ganosis " of Vitruvius. The part thus affected is yellowish and harder than the rest of the plaster. A careful chemical analysis, kindly made for the purpose of this article by Principal Laurie of Edinburgh shows that, although the small quantity of the material available makes it impossible to attain certainty, yet the substance may possibly be wax with the slight admixture of some greasy substance. On the other hand all the writer's other specimens show the colour laid on to all appearance " a fresco." The evidence of the coloured plaster in the house of about the 2nd century B.C. on Delos is wholly against Berger's view. The writer has many specimens of this, and they are all without exception coloured only on the surface. It is true that there are certain difficulties connected with Pompeian fresco practice, but the description of the process as a wet process in Vitruvius and Pliny is so absolutely unmistakable that Berger's theory must without hesitation be rejected. The history of the fresco technique remains at the same time obscure. Here again Berger offers an interesting suggestion which cannot be passed over in silence. If the Pompeian technique, as he believes, be a wax process on dry plaster, followed by some form of tempera, how did the fresco technique, which is known both in East and West in the later medieval period, take its rise? The early medieval age was not a time when a difficult and monumental technique of the kind is likely to have been evolved, but Berger most ingeniously connects it with that of mosaic work. In mosaic the wall surface is at first rough plastered and a second and comparatively thin coat of cement is laid over it to receive and retain the cubes of coloured glass, only so much cement being laid each morning as the worker will' over with his tesserae before night. It was the practice sometimes to sketch in water-colours on the freshly laid patch of cement the design which was to be reproduced in mosaic, and Berger points to the incontestable fact if this sketch were allowed to remain without being covered with the cubes it would really be a painting in fresco. This is the way he thinks that the frescoe practice actually began, and the period would be that of the decline of mosaic work in the West as the middle ages advanced. In spite of the attractiveness of these suggestions, we must reaffirm the view of this article that the testimony of Vitruvius is conclusive for the knowledge by the Romans of the early empire of the fresco technique. Why we do not find evidence of it far earlier cannot be determined, but it is worth noting that the success of the process depends on the plaster holding the moisture for a sufficient time, and this it can only do if it be pretty thick. In ancient Egypt and Mesopotamia, for example, the plaster used as painting ground was very thin, and especially in those hot climates would never have lent itself to fresco treatment. On the other side, the decline, and perhaps temporary extinction, of the technique in the early middle ages may be reasonably explained by the general condition of the arts after the break-up of the Roman Empire of the West. To return now to the technical questions from which this historical digression took its rise, it will be easily seen that the process of painting in fresco must be a rapid one, for it must be completed before the plaster has had time to dry. Hence only a certain portion of the work in hand is undertaken at a time, and onlyso much of the final coat of plaster, called by the Italians intonaco is laid by the plasterer as will correspond to the amount the artist has laid out for himself in the time allowed him by the condition of the plaster. At the end of this time the plaster not painted on is cut away round the outline of the work already finished, and when operations are recommenced a fresh patch is laid on and joined up as neatly as possible to the old. In the making of. these joints the ancient plasterer seems to have been more expert than the Italians of the Renaissance, and the seams are often pretty apparent in frescoes of the 15th and 16th centuries, so that they can be discerned in a good photograph. When they can be followed, they furnish information which it is often interesting to possess as to the amount that has been executed in a single day's work. Judging by this test, Mr Heath Wilson, in his Life of Michelangelo, computed that on the vault of the Sistine Michelangelo could paint a nude figure considerably above life size in two working days, the workmanship being perfect in every part. The colossal nude figures of young men on the cornice of the vault at most occupied four days each. The " Adam " (fig 34, Plate X.). was painted in four or perhaps in three. A day was generally occupied by the head of such figures, which were about to ft. high. Raphael, or rather his pupils, it is thus calculated, painted the Incendio del Borgo, containing about 350 sq. ft., in about forty days, the group of the young man carrying his father occupying three. The group of the Three Graces in the Villa Farnesina took five days at most. Luini, a most accomplished executant, could paint " more than an entire figure, the size of life, in one day " (Second Report, p. 37). It has been noticed as one of the difficulties about the Pompeian frescoes, that joints hardly occur, or at any rate that larger surfaces of plaster were covered by the painter at a single time than was the case among Renaissance artists, and a conjectural .explanation has been offered based on the fact that the ancient plaster ground, laid on in many successive coats while in each case the previous one was still humid, was thicker and would hold more moisture than the more modern intonaco, and would accordingly allow the artist longer time in which to carry out his work. Alberti, Armenini, and Palomino only contemplate one or two thin coats over the original rough cast, while Cornelius and his associates, who revived the process early in the 19th century, speak of an intonaco over the rough cast only about a quarter of an inch thick. A piece of plaster ground from Raphael's Loggie in the Vatican was found to be quite thin, and Donner calculated that the ancient grounds were on an average 3 in. thick, the modern only a little over 1 in. On such grounds work had necessarily to be finished within the day, and Cennino expressly says (ch. 67): " Consider how much you can paint in a day; for whatever you cover with plaster you must finish the same day." Hence almost invariably in Italian fresco practice every join means a new day's work. At Pompeii the plaster, it is thought, might have remained damp over night. In the Mount Athos Handbook tow was to be mixed with the plaster, undoubtedly to retard its drying. This necessarily rapid execution gives to well-handled frescoes a simplicity and look of directness in technique that are of the essence of the aesthetic effect of this form of the art. Hence Vasari is right when he extols the process in the words, " of all the ways in which painters work, wall-painting is the finest and most masterly, since it consists in doing upon a single day that which in other methods may be accomplished in several by going over again what has been done. . . . there are many of our craft who do well enough in other kinds of work, as for example in oil or tempera, but fail in this, for this is in truth the most manly, the safest, and most solid of all ways of painting. Therefore let those who seek to work upon the wall, paint with a manly touch upon the fresh plaster, and avoid returning to it when it is dry " (Opere, ed. Milanesi, i. 181). The process gives the artist another advantage in that his painting, being executed in the very material of the surface itself, seems essentially a part of the wall. It is lime painting on a, lime ground, and fabric and enrichment are one. This' can be noted in the Sala del Constantino in the Vatican at Rome, one of the stanze or suite of rooms decorated by Raphael and his associates. There are two figures here painted on the walls in oil, and though there is a certain depth and richness of effect secured in this medium, they are too obviously something added as an afterthought, while the figures in fresco seem an integral part of the wall. Work of this kind, finished in each part at a sitting, is what the Italians call buon fresco or " true fresco," and it has always been, as it was with Vitruvius, the ideal of the art, but at many periods the painters have had to rely largely on retouches and reinforcements after the plaster was dry. Cennino devotes the 67th chapter of his Trattato to a description of the process, and expressly tells us that the method he recommends is the one traditional in the school of Giotto, of which he himself was a direct scion. He is fully alive to the importance of doing as much as possible while the ground is wet, for " to paint on the fresh—that is, a fixed portion on each day—is the best and most permanent way of laying on the colour, and the pleasantest method of painting "; but an ordinary artist of the early part of the 15th century had not sufficient skill to do all that was required at the one moment. Observations made on the works executed by various Italian masters from the 14th to the 16th century show great varieties in this matter of retouching, but the subject need not be dwelt on as it involves no principle. Every painter of worthy ambition, who had entered into the spirit of his craft, would desire to do all he could " on the fresh," and would be satisfied with, and indeed glory in, the conditions and limitations of the noble technique. Masaccio, even at the beginning of the 15th century, is remarkable for the amount of fine pictorial effect he secured without reliance on retouching. It was second-rate artists, like Pinturicchio, who delighted to furbish up their mural pictures with stucco reliefs and gilding and to add touches of more brilliant pigments than could be used in the wet process. Giotto, Masaccio, Ghirlandajo, Michelangelo, Luini, are among. the frescanti proper, who represent the true ideals of the craft. The following notes upon the methods of the work are derived partly from observation of extant works and partly from the older treatises, but reference has also been made to modern practice in Germany and Italy, as information derived from this last source may be found useful by those who are disposed to-day to make essays in the process. To avoid loss of time it is essential that the necessary drawing should all be accomplished beforehand. Pozzo, a painter and writer of the end of the 17th century says, " everyone knows that before beginning to paint it is necessary to prepare a drawing and well-studied coloured sketch, both of which are to be kept at hand in painting the fresco, so as not to have any other thought than that of the execution " (First Report, p. 35). In Cennino's time it seems to have been the practice to square out the work full size from the sketch on to the surface of the rough cast before the intonaco was laid. This at any rate enabled the artist to see how his work as a whole would come in relation to the space provided for it, but the actual intonaco had to be laid piece by piece over this general sketch and the drawing of each portion repeated on the new surface. In the palmy days of Italian painting, however, as well as in modern times, the design has been drawn out on a full-sized cartoon, and this cartoon, or a tracing from it, has been transferred piece by piece to the freshly laid intonaco on which the painting is about to be executed. The drawing may be nailed against the wall, and the outlines passed over with a blunt-pointed stylus of some hard material, that by dinting the paper impresses on the yielding plaster a line sufficient to guide the painter in his work; or the outlines of the cartoon may be pricked and "pounced " with a little bag of red or black powder that will leave a dotted outline on the wall. The preparation of the intonaco itself is however a matter for much care. The lime should be prepared from a stone that is as far as possible pure carbonate of lime—the travertine of Tivoli, recommended by Vasari, is perfect for the purpose—and after it is burnt should be slaked with water and thoroughly macerated so that the lumps are all completely broken up. The slaked lime, of the consistency of a stiff paste, or as it is termed "putty," must be kept covered in from the air for a considerable period that varies according to different authorities from eight to twelve months to as many years. All experts, from Vitruvius downwards, are agreed on the necessity for this, but the exact scientific reason therefor does not seem to be quite clear. One advantage of the keeping is that the lime hydrate may take up a certain amountof carbonic acid, though not too much, from the air. Church says that, " not more than one-third or at most two-fifths of the lime should be converted into the carbonate " (p. 19); but Faraday (Fifth Report, p. 25) was of opinion that through lapse of time there was brought about a molecular change that divided the particles more thoroughly and gave the lime a finer texture so as to mix better with the pigments. At any rate, when Cornelius and his associates started the modern fresco revival at Rome, in 1815, an old workman who had been employed under Raphael Mengs directed their attention to this tradition, and they used lime that had been kept in a slaked condition, but still caustic—that is, still deprived of most of its carbonic acid, for twelve years! For mixing the plaster the proportions of lime to sand or marble dust vary; Cennino gives two of sand to one of " rich " or caustic lime, but the Germans used three of sand to one of lime. Whatever its exact constitution, the intonaco has to be carefully laid each morning over that part of the rough cast, previously well wetted, that corresponds to the amount laid out for the day's work. Contrary to the prescription of Vitruvius and Pompeian practice, which favours a polished surface, the moderns prefer a slight roughness or "tooth " on the intonaco. Painting should not begin, so Cornelius advised (First Report, p. 24), till " the surface is in such a state that it will barely receive the impression of the finger, but not so wet as to be in danger of being stirred up by the brush." The pigments are ready mixed in little pots, on a tin palette with a rim round the edge, or on a table, and in old Italian practice each colour was compounded in three shades—dark, middle and light. The water should be boiled or distilled, or should be rain-water; for spring-water often contains carbonate of lime that would derange the chemistry of the process. Again, on account of the chemical action that takes place during the process, the pigments have to be carefully selected. The palette of the fresco painter is indeed a very restricted one, and this is another reason of the broad and simple effect of the work. Practically speaking only the earth colours, such as the ochres raw or burned, can be used with safety; even the white has to be pure white lime (in Italian, bianco San-Giovanni), since lead white used in oil painting (Italian, biacca) is inadmissible. Vegetable and animal pigments are as a rule excluded, " very few colours of organic origin withstanding the de-composing action of lime " (Church, p. 28o). The brushes are of hog-bristles or otter-hair or sable, and have to be rather long in the hair. Round ones are recommended. According to early Italian practice, the painter would first outline the figures or objects, already drawn on the plaster, with a long-haired brush dipped in red ochre, and would then, e.g. in the case of the faces, lay in broadly with terre verte the shadows under the brows, below the nostrils, and round the chin, and bring down and fuse into these shadows the darkest of the three flesh-tints, with a dexterous blending of the wet pigments upon a surface that preserves their dampness. On the other side these half-tones are now modelled up into the lighter hues of the flesh. White may then be used in decided touches for the high lights, and the details of the eyes, mouth and other features put in without too much searching after accidents of local colour. Modern frescoists have found that " the tints first applied sink in and look faint, so that it is necessary sometimes to go over the surface repeatedly with the same colour before the full effect is gained " (First Report, p. 24), but it is well to allow in each case some minutes to elapse before touching any spot a second time. For the hair the Italians would make three tints suffice, the high lights again following with white. The draperies are broadly treated. After the whole has been laid in, in monochrome, with the green pigment, the folds would be marked out with the deepest of the three tints for shadow, and these shadows united by the middle tint. Lastly the lighter parts are painted up and finally reinforced with white. The work needs to be deftly touched, for too much handling of one spot may destroy the freshness of the tints and even rub up the ground. It is not necessary (as moderns have sometimes supposed) to put touch beside touch, never going twice over the same ground. So long as the pigments and the surface are wet the tints may be laid one over the other or fused at will, and may be " loaded " in some parts and in others thinly spread, the one essential being that a fresh and crisp effect shall not be lost. The wetness of the ground will always secure a certain softness in all touches, even those that give the strong high-lights, and so important is it that the plaster should not begin to dry, that it should be sprinkled if necessary with fresh water. The characteristic softness of the touches laid on " a fresco " is the more apparent when they are compared with those strokes of reinforcement which may be put on " a tempera " after the work is dry. Armenini says that the shadows may be finished and deepened by hatching, as in a drawing, with black and lake laid on with a soft brush with a medium of gum, size, or white and yolk of egg diluted with vinegar. Such retouches are always hard and " wiry," and are as much as possible to be avoided. As examples of execution in fresco no works are better than those of Luini. He painted rapidly and thinly, securing thereby a transparency of effect that did not however preclude richness. Heath Wilson indeed says of his painting that " it may be compared to that of Rubens; it is juicy, transparent, and clear; .. . his execution is light and graceful." No sounder model could be taken for modern work. The high-water mark of achievement in fresco painting was however reached by a greater than Luini—by Michelangelo in his painting of the Sistine Chapel roof. Considering that since his boyhood he had had no practical experience of the fresco process, and refused the commission as long as he could because he was not a painter but a sculptor, Buonarroti's technical success in the manipulation of the difficult process is still more astounding than the aesthetic result of the work as a creation of imaginative genius. He had to paint for the most part lying on his back in a sort of cradle, and working with his arms above his head, and had no skilled assistants; yet there is no quality in the work that strikes us more than its freshness and air of easy mastery, as if the artist were playing with his task. The fusion of the lights and shadows through the most delicate half-tones is accomplished in that melting fashion for which the Italians used the term sfumato or " misty," while at the same time the touches are crisp and firm, the accent here and there decided; and the artist's incomparable mastery of form gives a massive solidity to the whole (see fig. 34, Plate X.) In our own times and in English-speaking circles the fresco process has been discredited owing to the comparative failure of the experiments connected with the Houses of Parliament. On the condition of the frescoes there, as well as on that of the pictures in various other media, a series of Memoranda were made by Professor Church, and a select committee of the House of Lords took evidence on the subject as late as December 1906. Most of the frescoes executed in the forties and fifties of the 19th century had got into a deplorable state; but Church's belief was that the main cause of the decay was the sulphurous acid with which, owing to the consumption of coal and gas, the air of London is so highly charged. The action of this acid—a million tons of which are said to be belched out into the London atmosphere in every year—turns the carbonate of lime which forms the surface of the fresco into a sulphate, and it ceases to retain its binding power over the pigments. " The chemical change," he reports, " is accompanied by a mechanical expansion which causes a disruption of the ground and is the main cause of the destruction of the painting." It is a remarkable fact, however, that one of the frescoes in question, Sir John Tenniel's " St Cecilia," completed in 1850, painted very thinly and on a smooth surface, lasted well, and opposed " a considerable measure of successful resistance for nearly half a century on the part of a pure fresco to the hostile influence of the London atmosphere " (Church, Memorandum, iv. 1896). Abroad, experience was more favourable. The earliest frescoes of the modern revival—those by Cornelius and his associates from the Casa Bartholdy at Rome—are in a fairly good state in the National Gallery at Berlin. Such too is the condition of Cornelius's large fresco in the Ludwigskirche at Munich. The best modern frescoes, from the artistic point of view, in all Europe are those of about 185o by Alfred Rethel in the town-hall at Aix-la-Chapelle, and they are well preserved. The exterior frescoes on the Pinacotek at Munich have on the other hand mostly perished; but the climate of that city is severe in winter, and nothing else was really to be expected. We must not expect carbonate of lime to resist atmospheric influences which affect to a greater or less degree all mineral substances. § 36. Fresco-Secco.—(See Charles Heath Wilson, in appendix to Second Report of the Commissioners on the Fine Arts, London, 1843, p. 40; Church, Chemistry of Paints and Painting, 1901, p. 278). The process called " fresco-secco " is a method of lime painting on a plaster surface that has been allowed to dry. It is described by Theophilus in the Schedula of about A.D. 1100; and Mr Charles Heath Wilson in 1843 wrote of it as " extensively used in Italy at present and with great success." It is of course obvious that paintings must often be executed on walls the plastering of which is already dry, and on which the true fresco process is imprac-ticable. Some kind of painting in tempera is thus needful, and " fresco-secco " uses for this the lime that is the very constituent of the plaster. The process is thoroughly to drench the dry surface of the plaster the night before with water with which a little lime or baryta water has been mixed, and to renew the wetting the next morning. The artist then fixes up his cartoon, pounces the outlines, and sets to work to paint with the same pigments as used in buon fresco mixed with lime or baryta water or with a little slaked lime. If the wall become too dry a syringe is used to wet it. The directions given by Theophilus (i. 15) correspond with this modern practice. " When figures or representations of other things," he says, "are to be delineated on a dry wall, it must be forthwith moistened with water till it is thoroughly wet. On this wet ground all the colours must be laid that are required, and they must be all mixed with lime, and will dry with the wall so that they adhere to it." Mr C. H. Wilson praises the work for its convenience, economy, and ease of execution, and notes that " for ornament it is a better method than real fresco, as in the latter art it is quite impossible to make the joinings at outlines owing to the complicated forms of ornaments," but says that " it is in every important respect an inferior art to real fresco. Paintings executed in this mode are ever heavy and opaque, whereas fresco is light and transparent." He declares also for its durability, but Professor Church states what seems obvious, that " the fixation of the pigments . . . is less complete " than in real fresco though depending on the same chemical conditions(Second Report, 1843, p. 40; Chemistry, p. 279). § 37. Stereochromy or Water-Glass Painting.—(See Chemischtechnische Bibliothek, Band lxxviii., Die Mineral-Malerei, von A. Keim, Wien, &c., 1881; Rev. J. A. Rivington in Journal of the Society of Arts, No. 1630, Feb. 15, 1884; Mrs Lea Merritt and Professor Roberts Austin in Journal of the Society of Arts, No. 2246, Dec. 6, 1895; F. G. Cremer, Beitrage zur Technik der Monumental-Malverfahren, Dusseldorf, 1895). Akin to " fresco-secco," in that a mineral agent is used to secure the adhesion of the colouring matter to the plaster, is the process known as stereochromy or water-glass painting. It is not a traditional process, but an outcome of comparatively modern chemical research, and is not yet a century old. It is based on the properties of the substance called water-glass, a silicate of potassium or of soda, perfected by the German chemist Von Fuchs about 1825. A process of painting called " stereochromy " was soon after evolved, in which pigments of the same kind as those used in fresco, mixed only with distilled water and laid on a prepared plaster ground, were afterwards fixed and securely locked up by being drenched with this sub-stance, which is equivalent to a soluble glass. Some of the mural paintings in the Houses of Parliament, notably those by Maclise, were executed in this process. Improvements were more recently effected in the process with which the names of Keim and Recknagel of Munich are connected, and in this form it has been used a good deal in Germany in the last quarter of the 19th century both in interiors and in the open air. For example, in 1881 Professor Schraudolph of Munich painted in this process the front of the Hotel Bellevue in that city. This improved water-glass painting was introduced to notice in England in a paper read before the Society of Arts by the Rev. J. A. Rivington on the 13th of February 1884, and printed in the Journal of the society, No. 1630. A more recent description is contained in F. G. Cremer's Beitrage. The recipe for the preparation of the actual medium is as follows: 15 parts pounded quartzsand, io parts refined potash, 1 part powdered charcoal are mixed together and fused for 6 to 8 hours in a glass furnace. The resultant mass when cold is reduced to powder and boiled for 3 or 4 hours in an iron vessel with distilled water till it dissolves and yields a heavy syrupy liquor of strongly alkaline reaction. This can be diluted with water, and in the process is applied hot. The ground is very carefully prepared, and over a thoroughly sound and dry backing a thin coat of plaster is laid, composed of only 1 part lime to 5 or 8 parts selected sand and pounded marble with a slight admixture of infusorial earth. The object is to obtain a homogeneous porous ground that can be thoroughly permeated with the solution, and to help to secure this the intonaco when dry is sprayed with hydrofluo-silicic acid to dissolve away the crystalline skin of carbonate of lime formed on the surface and to "open the pores " of the plaster. The surface of the painting ground, which is left with a decided " tooth " upon it, is then well soaked with the solution, and when dry will be found " hard but perfectly absorbent and ready for painting." The pigments consist in the usual ochres and earths; chrome reds, greens, and yellows; Naples yellow (antimoniate of lead); cobalt blue and green; and artificial ultramarine; terre verte, &c., with zinc white or baryta white. It is important however to note, that the pigments (which can be supplied by Messrs Schirmer, late Faulstich, of Munich, and many other firms) are mixed with various substances so as to render uniform the action upon them of the fixing solution and neutralize the action of its alkalies. The operations of painting, in which only distilled water is used with the colours, are easy and admit of considerable freedom. " Every variety of treatment is possible, and the method adapts itself to any individual style of painting." The work can be left and resumed at will. After the painting is dry there comes the all-important final process of fixing with the water-glass solution. This is sprayed on in a hot state by means of a special apparatus, and the process is repeated till the wall can absorb no more, the idea being that the substance will penetrate right through to the wall, and when set will bind pigments, intonaco, rot'gh plastering and wall into one hard mass of silicate that will be impervious to moisture or any injurious agencies. The last paragraph of the official account of the Keim process issued in 1883 for the guidance of those contemplating mural work runs as follows: " The fixing of the picture is accomplished by means of a hot solution of potash water-glass, thrown against the surface by means of a spray-producing machine in the form of a very fine spray. This fixing done, by several repetitions of the process, a solution of carbonate of ammonia is finally applied to the surface. The carbonate of potash, which is thus quickly formed, is removed by repeated washings with distilled water. Then the picture is dried by a moderate artificial heat. Finally a solution of paraffin in benzene may be used to enrich the colours and further preserve the painting from adverse influences." § 38. Spirit Fresco or the " Gambier Parry " Process, with modifications by Professor Church.—(See Spirit Fresco Painting: an Account of the Process, by T. Gambier Parry, London, 1883; Church, Chemistry of Paints and Painting, 288 seq.). This process is also one of quite modern origin, but in Great Britain, at any rate, it is now very popular. Mr Gambier Parry, who invented and first put it into practice, claims for it that it " is not the mere addition of one or more medium to the many already known, but a system, complete from the first preparation of a wall, to the last touch of the artist," and that the advantages it offers are " (I) durability (the principal materials being all but imperishable); (2) power to resist external damp and changes of temperature; (3) luminous effect; (4) a dead surface; (5) freedom from all chemical action on colours." The theory of the process is much the same as that of stereochromy, the drenching of the ground with a solution that forms at the same time the medium of the pigments, so that the whole forms when dry a homogeneous mass. The solution or medium is however not a mineral one, but a combination of oils, varnishes and wax, the use of which makes the process nearly akin to that of oil painting. The objection to the use of oil painting proper on walls is the shininess of effect characteristic of that system, which is in mural work especially to be avoided, and "spirit fresco " aims at the elimination of the oleaginous element and the substitution of wax which gives the "matt " surface desired. Mr Gambier Parry directs a carefully laid intonaco of ordinary plaster suitable for fresco on a dry backing, " the one primary necessity " being that the intonaco " should be left with its natural surface, its porous quality being absolutely essential. All smoothing process or ' floating ' with plaster of Paris destroys this quality. All cements must be avoided." When dry the surface of the wall must be well saturated with the medium, for which the following is the recipe: pure white wax 4 oz. by weight; elemi resin 2 oz. by weight dissolved in 2 oz. of rectified turpentine; oil of spike lavender 8 oz. by measure; copal varnish about 20 oz. by measure. These ingredients are melted and boiled together by a process described in his paper, and when used for the wall the medium is diluted in one and a half its bulk of good turpentine. With this diluted solution the wall is well soaked, and the directions continue, " after a few days left for evaporation, mix equal quantities of pure white lead in powder and of gilder's whitening in. the medium slightly diluted with about a third of turpentine, and paint the surface thickly, and when sufficiently evaporated to bear a second coat, add it as thickly as a brush can lay it. This when dry, forwhich two or three weeks may be required, produces a perfect surface " both white and absorbent. The pigments, which are practically the same as those used in oil painting, must be ground in dry powder in the undiluted medium, and when prepared can be kept in tubes like oil colours. Solid painting with a good deal of body is recommended and pure oil of spike is freely used as painting medium. Pure spike oil may also be washed over the ground before painting " to melt the surface (hence the name Spirit Fresco) and prepare it to incorporate the colours painted into it." The spike oil is " the one common solvent of all the materials; . the moment the painter's brush touches the surface (already softened, if necessary, for the day's work) it opens to receive the colours, and on the rapid evaporation of the spike oil it closes them in, and thus the work is done." The oil of spike lavender, it may be noticed, is an essential oil prepared from Lavandula spica. Professor Church has suggested improvement in the composition of the medium by eliminating the " doubtful constituents " elemi resin and bees'-wax and substituting paraffin wax, one of the safest of materials, dissolved in non-resinifiable oil of turpentine. This is mixed as before with copal varnish and used in the same way and with the same or better results as Mr Gambier Parry's medium. § 39. Oil Processes of Wall Painting.—The use of the oil medium for painting on plaster in medieval days opens up a much debated subject on which a word will be said in connexion with oil painting in general. In the later Renaissance period in Italy it came into limited use, and Leonardo essayed it in an imperfect form and with disastrous result in his " Last Supper " at Milan. Other artists, notably Sebastiano del Piombo, were more successful, and Vasari, who experimented in the technique, gives his readers recipes for the preparation of the plaster ground. This with Cennino (ch. 90) had consisted in a coat of size or diluted egg-tempera mixed with milk of fig-shoots, but later on there was substituted for this several coats of hot boiled linseed oil. This was still in common use in the 16th century, but Vasari himself had evolved a better recipe which he gives us in the 8th chapter of his " Introduction " to Painting. Over undercoatings of ordinary plaster he lays a stucco composed of equal parts of lime, pounded brick, and scales of iron mixed with white of egg and linseed oil. This is then grounded with white oil toned down with a mixture of red and yellow easily drying pigments, and on this the painting is executed. In Edinburgh and other places Mrs Traquair has recently carried out wall paintings on dry plaster with oil colours much thinned with turpentine. The ground is prepared with several coats of white oil paint, and the finished work is finally varnished with the best copal carriage varnish. In most cases oil painting intended for mural decoration has been executed on canvas, to be afterwards attached to the wall. This is the case more especially in France, and also in America at the Boston public library and other places. The effort here is to get rid of the shiny effect of oil painting proper by eliminating as far as practicable the oil. As this however serves as the binding material of the pigments the procedure is a risky one. To suppress the oil and to secure a " matt " surface Mr E. A. Abbey employed at Boston and elsewhere, as a medium for painting with ordinary oil colours, wax dissolved in spike oil and turpentine. In France Puvis de Chavannes used some preparation to secure a matt effect in his fine decorative oil painting on canvas. § 40. Tempera Painting on Walls.—This is a very ancient and widely diffused technique, but the processes of it do not differ in principle from those of panel painting in the same method. It is accordingly dealt with under tempera painting in general (§ 43). § 41. Encaustic Painting on Walls.—(See Schultze-Naumburg, Die Technik der Malerei, p. 122 seq.; Paillot de Montabert, Traite complet de la peinture, vol. ix.). It has been already mentioned that wax is employed in modern mural painting in order to secure a matt surface. Many pictures have been carried out within the last century on walls in a regular wax medium that may or may not represent an ancient process. Hippolyte Flandrin executed his series of mural pictures in St Vincent de Paul and St Germain des Pres in Paris in a process worked out by Paillot de Montabert. Wax dissolved in turpentine or oil of spike is the main constituent of the medium with which the wall is saturated and the colours ground. Heat is used to drive the wax into the plaster. A German recipe prepared by Andreas Muller in Dusseldorf has been used for mural paintings in the National Gallery, Berlin. 4.90 In this one part virgin wax is dissolved in two parts turpentine with a few drops of boiled linseed oil. The pigments are ground in boiled linseed oil with the addition of this medium. The plaster ground, well dried, is soaked with hot boiled linseed oil diluted with an equal quantity of turpentine. It is then grounded with several coats of oil paint for a priming and smoothed with pumice stone. The painting can be executed in a thin water colour technique or with a full body, and dries lighter than when wet and with a dead surface. § 42. Encaustic Painting in general in Ancient and Modern Times.—(See Cros and Henry, L'Encaustique et les autres procedes de la peinture chez les anciens, Paris, 1884; Flinders-Petrie, Hawara, &c., London, 1889; 0. Donner v. Richter, Uber Technisches in der Malerei der Allen, Munich, 1885; Berger, Beitrage zur Entwickelungs-Geschichte der Maltechnik, ii. 185 seq.; Munich, 1904). Although in modern mural painting wax is employed to secure a matt surface, in ancient times it appears to have been valued rather from the depth and intensity it lent to colours when it was polished. It there represented an attempt to secure the same force and pictorial quality which in modern times are gained by the use of the oil medium. We are told of it by the ancients that it was a slow and troublesome process, and the name of it, meaning " burning in," shows that the inconvenience of a heating apparatus was inseparable from it; yet it seems at the same time to have been a generally accepted technique, and Greek writers from Anacreon to Procopius treat, " wax " as the standard material for the painter. Nay more, hardly a day now passes with-out every one of us bearing testimony in the words he uses to the importance of the technique in antiquity. The Etymologicum magnum of the 12th century makes the process stand for painting generally (E'yKEKavj fvfl-EEw'ypa(tmOv ), and the name " encaustic " came to be applied not only to painting but also to sumptuous calligraphy. Then it was applied to writing in general, and the name still survives in the Italian inchiostro and our own familiar " ink " (Eastlake, Materials, i. 151). The technique of ancient encaustic has given rise to much discussion which till recently was carried on chiefly on a literary basis. Fresh material has been contributed by the discovery, in the eighties of the 19th century, in Egypt of a series of portraits on mummy cases, executed for the most part in a wax process, and dating probably from the first two or three centuries A.D. Previous to this discovery there was little material of a monumental kind, though what appears to be the painting apparatus of a Gallo-Roman artist in encaustic was found in 1847 at St Medard-des-Pres in La Vendee, and has been often figured. It should be stated at the outset that the modern process of dissolving wax in turpentine or an essential oil like oil of spike was not known to the ancients, who however knew how to mix resinous substances with it, as in the case of ship-painting (Pliny xi. 16; Dioscorides i. 98). They also saponified wax by boiling it with potash so as to form what was called " Punic wax " (Pliny xxi. 84 seq.), and this emulsion may be reduced with water, and at the same time combines with oil and with size, gum, egg and other temperas.. Wax, Pliny says, may be coloured and used for painting—ad edendas similitudines (loc. cit.); but as the name " encaustic " implies, and as we gather from another of Pliny's phrases, ceris pingere ac picturam inurere (xxxv. 122), heat was an essential part of the process. Hence the material must have been employed as a rule in a more or less solid form and liquefied each time for use, and not in the form of a diluted solution or emulsion which could be made serviceable cold. It is true that Punic wax mixed with a little oil is prescribed by Vitruvius (vii. 9, 3) as a solution for covering and locking up from the air a coat of the changeable pigment vermilion laid on a wall (see § 35), but the solution is used hot and driven in by application of a heating apparatus. The accounts of the technique furnished to us by Pliny can be brought into connexion with the actual remains, and Berger and others have succeeded fairly well in imitating these by processes evolved from the ancient notices. It is unfortunate that the most important passage of Pliny (xxxv. 149) appears corrupt. It runs in the received text as follows: Encausto pingendi duo fuere antiquitus genera, cera et in ebore cestro, id est[TECHNIQUE vericulo, donee classes pingi coepere. Hoc tertium accessit resolutis igni ceris penicillo utendi, quae pictura navibus nec sole nec sale ventisve corrumpitur. Here three kinds of encaustic painting are mentioned, two old and one new (the comparative chronology of the processes need not come into question), and in the two last cases the distinction is that between two instruments of painting, the cestrum and the penicillus or brush. It is natural to suggest that instead of the word cera, which, as wax is the material common to all encaustic processes, need not have been introduced and on manuscript authority may be suspected, some word for a third instrument of painting should be restored. Berger, with some philological likelihood, conjectures the word cauterio, which means properly a " branding-iron," but which he believes to be a sort of hollowed spatula or spoon with a large and a small end by which melted waxes of different colours might be taken up, laid on a ground, such as a wooden panel, and manipulated in a soft state as pictorial effect required. Instruments of the kind were found in the Gallo-Roman tomb in La Vendee. The second kind of painting with the cestrum or vericulum was on ivory and must have been on a minute scale. The "cestrum" was certainly a tool of corresponding size, and some have seen in it a sort of point or graver, such as that with which the incised outlines were made on the figured ivory plaques in the Kertch room at St Petersburg (see below); others a small lancet-shaped spatula like the tools that sculptors employ for working on plaster. The brush, with which melted waxes could be laid on in washes, as was the case on ships, needs no explanation. An examination of the portraits from the mummy cases (see fig. 35) makes it quite clear that the brush was used with coloured melted waxes to paint in, in sketchy fashion, the draperies and possibly to underpaint the flesh and hair, while the flesh was executed in a more pastes style, with waxes in a soft condition laid on and manipulated with some spatula-like instrument, which we may if we like call " cauterium " or " cestrum." The marks of such a tool are on several of the heads unmistakably in evidence, and may be seen in specimens in the London National Gallery. There is a difference of opinion however as to the constitution of the wax. Donner von Richter holds that the wax was "Punic," i.e. a kind of emulsion, and was blended with oil and resinous balsams 'so as to be transformed into a soft paste which could be manipulated cold with the spatula. Heat for " burning in " (picturam inurere) he thinks was afterwards applied, with the effect of slightly fusing and blending the coloured waxes that had been in this way worked into a picture. Berger, on the other hand, believes that the coloured wax pastes were manipulated hot with the " cauterium," which would be maintained in a heated condition, and that there was no subsequent process of " burning in." Flinders Petrie is of opinion that, even in the (From a photograph by W. A. Mansell & Co.) TECHNIQUE] case of the washes laid on with the brush, pure melted wax was employed and not a compound or emulsion, such as is generally assumed. Berger believes in a mixture of wax, oil and resin. It is interesting to note that the distinguished modern painter, Arnold Bocklin, executed his picture of " Sappho " in coloured pastes composed of copal resin, turpentine and wax, manipulated with a curved spatula, and that he applied heat to fuse slightly the impasto. He believed he obtained in this way a brilliancy not to be compassed with oils. The nature of the " cestron " technique on ivory is not known. The only existing artistic designs in ivory are executed by engraved lines, and these are sometimes filled in with coloured pastes. Exquisite work in this style exists in the Hermitage at St Petersburg, and there are examples in other museums, but this can hardly be termed encaustic painting. A better idea of the laboriously executed miniature portraits of which Pliny tells us can be gained from the small medallion portraits modelled in coloured wax that were common at the Renaissance period and are still executed to-day. In these however the smaller details are put in with the brush and pigment. It is known from the evidence of the Erechtheum inscription that \the encaustic process was employed for the painting of ornamental patterns on architectural features of marble buildings, but there is still considerable doubt as to the technique employed in such forms of decorative painting as the colouring of the white plaster that covered the surfaces of stonework on monumental buildings in inferior materials. Polychrome ornament on terra-cotta for architectural embellishment may have been fixed by the glaze as in ordinary vase painting, but Pliny says that Agrippa figulinum opus encausto pinxit in his Thermae (xxxvi. 189). The technique of the polychrome lecuthi and of the polychrome terra-cotta statuary is not certain. The later history of wax painting after the fall of the Western Empire is of interest in connexion with the evolution of the painter's technique as a whole. Its possible relation to oil painting will be noticed later on. Here it is enough to note that the so-called Lucca MS. of the 8th century mentions the mingling of wax with colours, and the Byzantine Mount Athos Handbook, recording probably the practice of the 1th century, gives a recipe for an emulsion of partly saponified wax with size as a painting medium. A recipe of the 15th century quoted by Mrs Merrifield from the MSS. of Le Begue gives a similar composition that can be thinned with water and used to temper all sorts of col . § 43. Ter era Painting. [Cennino's Trattato, in the English edition with terminal essays by Mrs Herringham (London, 1899), is the best work to consult on the subject. The Society of Painters in Tempera published in 1907 a volume of Papers on the subject. F. Lloyd's Practical Guide to Scene Painting and Painting in Distemper (London, 1879), is chiefly about the painting of theatrical scenery, and this subject is also dealt with in articles by William Telbin in the Magazine of Art (1889), pp. 92, 195.] The binding substances used in the tempera processes may be classed as follows: (r) Size, preferably that made from boiling down cuttings of parchment. Fish-glue, gum, especially gum tragacanth and gum arabic (the Senegal gum of commerce); glycerin, honey, milk, wine, beer, &c. (2) Eggs, in the form of (i) the yolk alone, (ii) the white alone, (iii) the whole contents of the egg beaten up, (iv) the same with the addition of the milk or sap of young shoots of the fig-tree, (v) the contents of the egg with the addition of about the same quantity of vinegar [(iv) was used in the south, (v) north of the Alps]. (3) Emulsions, in which wax or oil is mingled with substances which bring about the possibility of diluting the mixture with water. Thus oil can be made to unite mechanically (not chemically) with water by the interposition either of gum or of the yolk of egg. Of these materials it may be noted that a size or gum tempera is always soluble in water, and is moreover always of a rather thin consistency. The latter applies also to white of egg. On the other hand the yolk of an egg makes a medium of greater body, and modern artists, especially in Germany, have painted in it with a full impasto. The yolk of egg or the whole egg slightly491 beaten up may be used to temper powdered pigments without any dilution by means of water, and the stiffest body can in this way be obtained. The medieval artists seem however always to have painted with egg thinly, diluting the yolk with about an equal quantity of water. Their panels show this, and we can argue the same from the number of successive coats of paint prescribed by Cennino and other writers. The former (ch. 165) mentions seven or eight or ten coats of colours tempered with yolk alone, that must have been well thinned with water. This point will be returned to later on. The yolk of egg is really itself an emulsion as it contains about 3o% of oil or fatty matter, though in its fluid state it combines readily with water. " Egg yolk," writes Professor Church (Chemistry, p. 74 ), must be regarded as essentially an oil medium. As it dries the oil hardens," and ultimately becomes a substance not unlike leather that is quite impervious to moisture. Hence while size tempera when dry yields to water egg tempera will resist it. Sir William Richmond gave a proof of this in evidence before a committee of the House of Lords in November 1906, describing how he had exposed a piece of plaster painted with yolk of egg medium to all weathers for six months on the roof of a church and found it at the end perfectly intact. As to the milk of young fig-shoots,, it is interesting to know from Principal Laurie (" Pigments and Vehicles of the Old Masters," in Journal of the Society of Arts, Jan. 15, 1892, p. 172) that " fig-tree belongs to the same family as the india-rubber tree, and its juice contains caoutchouc." He says, " doubtless the mixture of albumen and caoutchouc would make a very tough and protective medium." With regard to the historical use of these different media, the medieval Italians used almost exclusively the yolk of egg medium, and this is also the favourite tempera of the moderns. In fact in Italy the word " tempera," as used by Vasari and other writers, generally means the egg medium. On the other hand size or gum was more common north of the Alps. It is in most cases very difficult to decide what temperas were in vogue in different regions and at the various epochs of the art, and the following must not be taken for more than an approximate statement of the facts. As far as it is known, the binding material in ancient Egypt was for the most part size, while Greek influence from about 600 B.C. onwards may have led to the use of wax emulsion (Punic wax). For paintings on mummy cases, and on papyrus scrolls, the medium may have been size or gum. Professor Flinders Petrie says it was acacia gum. The wall paintings of ancient Mesopotamia as well as those of India and the farther East generally were all in tempera, and it is noteworthy that recipes and technical practices of the East and of the West seem to be curiously alike. The exact media used are doubtful. The same doubt exists with regard to the exact processes of wall and panel painting in tempera in ancient Greece and Italy, in the East, in Byzantine times, and in the early middle ages both north and south of the Alps. The materials and processes mentioned by Pliny or in the various technical handbooks are on the whole clearly established, but it is very difficult to say in particular cases what was the actual technique employed. Any certainty in this matter must be based on the results not only of superficial examination but of analysis, and the very small quantities of the materials that can be placed at the disposal of the chemist make it often impossible to arrive at a satisfactory diagnosis. A story in Pliny (xxxv. 102) shows that the Greek panel painters, when not " encaustae," used a water tempera, but whether size or egg was its main constituent we do not know. Apelles is said to have covered his finished panels with a thin coat of what Pliny calls " atramentum," which may have been a white of egg varnish, for spirit varnishes were not known in antiquity (Berger i. and ii. 183), and the Greeks do not seem to have used drying oils nor varnishes made with these. Byzantine panel painting, according to the Mount Athos Handbook, was executed as a rule in an egg tempera (Berger iii. 75), and this technique was followed later on in Italy. For Greek and Etruscan (Italian) wall-paintings of the pagan period; for late Roman wall-paintings north of the Alps, and for Romanesque and Gothic wall-paintings, 492 we have to choose amongst the theories of size or egg tempera, wax tempera (emulsion), and the lime painting in " fresco secco described by Theophilus. When we come to the panel painting from the 12th to the 15th century we are on surer ground. For the north we have the technical directions of Theophilus, for the south those of Cennino. Theophilus (i. ch. xxvii.) prescribes a tempera of gum from the cherry tree, and, with some pigments, white of egg. The finished panel was to be covered with an oil varnish (vernition). Cennino prescribes a tempera of the yolk of egg alone, half and half with the pigments, which have been finely ground in water and are very liquid, so that there might be in the ultimate compound about as much water as egg. A tempera of the whole egg with the milk of fig-shoots he recommends, not for panels, but for retouching fresco-work on the wall when it is dry. Tempera panels painted with egg yolk are, like the gum tempera panels of Theophilus, to be varnished with vernice liquida (oil varnish). In these media were executed all the fine tempera panels of the early Italian and early German schools of the 15th century, and these represent a limited, but within its bounds a very perfect and interesting, form of the painter's art. A word or two may be said here about the various subsidiary processes connected with 14th and 15th century panel painting, which are of great interest as showing the conscientious, and indeed devotional spirit in which the operations were carried out. At the outset of his Traitato Cennino gives a list of the processes the panel painter has to go through, and in subsequent chapters he describes minutely each of these. The artist must " know how to grind colours, to use glue, to fasten the linen on the panel, to prime with gesso, to scrape and smooth the gesso, to make reliefs in gesso, to put on bole, to gild, to burnish, to mix temperas, to lay on grounding colours, to transfer by pouncing through pricked lines, to sharpen lines with the stylus, to indent with little patterns, to carve, to colour, to ornament the panel, and finally to varnish it." The preliminary operations, before the artificer actually begins to " colour " or paint, will take him six years to learn, and it requires with Cennino half a hundred chapters to describe them. The wooden panel is carefully compacted and linen is glued down over its face, and over this is laid, in many successive coats, a gesso ground of slaked plaster of Paris mixed with size, with which composition raised ornaments, such as the nimbi of saints, &c., can be modelled. Both these and the flat parts of the panel are scraped and smoothed till they are like ivory. The design of the picture is then drawn out on the panel, and the outlines sharpened up with the utmost precision. The gilding of the background and of the carved wo dwork in which the panel is set now follows. Armenian bole, gr and finely with white of egg diluted with water, is spread over t e gesso and carefully burnished as a ground for water gilding with white of egg. The gold is then burnished till it appears almost dark (in the shadow) from its own refulgence. The delicate indented patterns which are so charming on the gilded grounds of the painted panels on East Anglian screens, such as that at Southwold, are stamped with little punches, and Cennino says this is one of the most beautiful parts of the art. In the actual painting, which is on the non-gilded part of the panel, the utmost attention is paid to the ornamentation of brocaded draperies, in which gold is used as a ground and is made to show in parts, while glazes of pigment mixed with drying oil are also used. Directions for painting the flesh, which is to be done after the draperies and background, are precise. There is an under-painting in a mono-chrome of terra verte and white, and over this in successive coats of great thinness the flesh-tints are spread, every tint being laid in its right position on the face, the darkest flesh-tint being shaded down to the terra verte and softened off in a tender sfumato manner. Many coats are superimposed, but the green ground is still to remain slightly 'visible. At the last the lightest flesh-tint is used to obtain the reliefs and the high lights are touched in in white. The outlines are sharpened up with red mixed with black. The varnishing process should be delayed for at least a year, and the varnish, which was evidently thick, is to be spread by the fingers over the painted surfaces, care being taken not to let the varnish go over the gold ground. This should be done if possible in the sun, but Cennino says that if the varnish be boiled it will dry without being placed in the sun. The process thus described is not what we should call, in the modern sense, painting, for the precision and conventionality of the work and the great importance given to subsidiary details are quite opposed to the spirit of the art since the 16th century. Nevertheless, the naive simplicity of the design and the exquisite delicacy of the finish have an unfailing charm. We feel, as Cennino says, that the artist has loved and delighted in his work, and regarded his patient manipulation as a religious act. A modern artist in tempera specially praises the old work for its " breadth, transparency and purity of colour," qualities " owing to the gradual[TECHNIQUE bringing forward of the picture from a simple outline of extreme beauty." "This outline is never lost; its beautifully opposed and harmonizing lines and masses are retained to the end, even strengthened and accentuated, giving great distinctness at a distance, even when not actually visible. A perfectly modulated monochrome of light and shade fills the outline, apparent through the overlaid glory of colour, over which again is thrown a veil of atmosphere, a refulgence of light, a suggestion of palpitating space " (Mrs Herringham's Cennino, p. 218). A difficulty in the technique is the rapid drying of the medium, that prevents the fusing of the colours together in the impasto, which is possible in oil painting. Woltmann (History of Painting, Eng. trans. i. 406) thought that in the north honey was mixed with the white of egg or size to prevent too rapid drying, and he wrote, " this method rendered possible a liquid and softly gradated handling, and though the Italian variety of tempera allowed greater depth in the shadows, the northern gave on the whole greater brightness." In Italy, owing to the rapid drying of the egg-yolk, modelling was often secured by hatching, which is not so pleasing in its effect as the other method of superimposing thin coats of paint one over the other till the proper effect of shading is secured. One notable quality of tempera is its transparency, which is referred to by Cennino when he says that the original under-painting of terra verte is never to be wholly obliterated. The well-known group of the " Three Graces," from Botticelli's large panel of the " Allegory of Spring," at Florence, gives the quality of tempera painting very aptly (see fig. 36, Plate X.). There is a Society of Painters in Tempera in London, and some artists are enthusiastic in their admiration of the process for its purity, sincerity and permanence. Under the heading " tempera " should be noticed another style of painting with a water-medium that is executed as a rule on a large scale and in a comparatively slight fashion. Painting for the purposes of temporary decoration on canvas or wood, so much used in the Italian cities of the Renaissance period, is of this kind. Large cartoons in colour for mural pictures or tapestry, of which Raphael's cartoons are the most famous examples, are other examples; while in modern times the technique is chiefly employed in theatrical scene painting. The pigments are tempered with size or gum, and body is given to them by whitening, pipe-clay or similar substance. Work executed in this medium dries much lighter than when it is put on, and to execute it effectively, as in the case of stage scenery, requires much skill and practice. " In the study of the art of distemper painting a source of considerable embarrassment to the inexperienced eye is that the colours when wet present such a different appearance to what they do when dry." So writes F. Lloyds, but W. Telbin, though he recognizes this difficulty, extols the process. " A splendid material distemper! For atmosphere unequalled, and for strength as powerful as oil, in half an hour you can do with it that which in water or oil would take one or two days!" The English word " distemper" and the French " gouache " are commonly applied to this style of broad summary painting in body-colour. " Distemper" to English ears suggests house-decoration, " tempera " the work of the artist. § 44. Oil Painting.—(See Eastlake, Materials for a History of Oil Painting (London, 1847); Merimee, De la peinture a l'huile (Paris, 1830); Berger, Beitrage zur Entwicklungs-Geschichte der Maltechnik, esp. iii. 221 sqq., and iv. (Munich, 1897), &c.; Dalbon, Les Origines de la peinture a l'huile (Paris, 1904); Ludwig, Uber die Grundsdtze der Oelmalerei (Leipzig, 1876); Lessing, Uber das Alter der Oelmalerei, 1774.) Oil painting is an art rather of the north than of the south and east, for its development was undoubtedly furthered by the demand for moisture-resisting media in comparatively damp climates, and, moreover, the drying oils on which the technique depends were but sparingly prepared in lands where olive oil, which does not dry, was a staple product. Certain vegetable oils dry naturally in the air by a process of oxydization, and this drying or hardening is not accompanied by any considerable shrinking, nor by any change of colour; so that oil and substances mixed with it do not alter in volume nor in appearance as a consequence of the drying process. There may be a slow subsequent alteration in the direction of darkening or becoming more yellow; but this is another matter. Among these oils the most important is linseed oil extracted from the seeds of the flax plant, poppy oil from the seeds of the opium poppy, and nut oil from the kernels of the common walnut. With these oils, generally linseed, ordinary tube colours used by painters in oil are prepared, and oil varnishes, also used by artists, are made by dissolving in them' certain resins. Their natural drying qualities can be greatly aided by subjecting them to heat, and also by mingling with them chemical substances known as " dryers," of which certain salts of lead and zinc are the most familiar. How far back in antiquity such oils and their proper-ties were known is doubtful. Certain varnishes are used in Egypt on mummy cases of the New Empire and on other surfaces, and, though some of these are soluble in water, others resist it, and may be made with drying oils or essential oils, though the art of distilling these last cannot be traced back in Egypt earlier than the Roman imperial period. (See Berthelot, La Chimie au moyen age, i. 138 (Paris, 1893). When Pliny tells us (xiv. 123) that all resins are soluble in oil, we might. think he was contemplating a varnish of the modern kind. Elsewhere, however (xxiv. 34), he prescribes such a solution as a sort of emollient ointment for wounds, so it is clear that the oil he has in view is non-drying olive oil that would not make a varnish. In two passages of his Natural History (xv. 24–32, xxiii. 79–96) Pliny discourses at length on various oils, but does not refer to their drying properties. There is really no direct evidence of the use among the Greeks and Romans of drying oils and oil varnishes, though a recent writer (Cremer, Untersuchungen fiber den Beginn der Oelmalerei, Duss., 1899) has searched for it with desperate eagerness. The chief purpose of painting for which such materials would have been in demand is the painting of ships, but this we know was carried out in the equally waterproof medium of wax, with which resin or pitch was commingled by heat. The earliest mention of the use of a drying oil in a process connected with painting is in the medical writer Aetius, of the beginning of the 6th century A.D., who says that nut oil dries and forms a protective varnish over gilding or encaustic painting. From this time onwards the use of drying oils and varnishes in painting processes is well established. The Lucca MS. of the 8th or 9th century A.D. gives a receipe for a transparent varnish composed of linseed oil and resin. In the Mount Athos Handbook " peseri," or boiled linseed oil, appears in common use, and with resin is made into a varnish. In the same treatise also we find a clear description of oil painting in the modern sense; but since the dates of the various portions of the Handbook are uncertain, we may refer rather to Theophilus (about A.D. 1100), who indicates the same process with equal clearness. The passages in Theophilus (i. chs. xx. and xxvi.–xxviii.) are of the first importance for the history of oil painting. He directs the artificer to take the colours he wishes to apply, to grind them carefully without water in oil of linseed prepared as he describes in ch. xx., and to paint therewith flesh and drapery, beasts or birds or foliage, just as he pleases. All kinds of pigments can be ground in the oil and used on wooden panels, for the work must be put out in the sun to dry. It is noteworthy that Theophilus (ch. xxvii.) seems to confine this method of painting to movable works (on panel, in opere ligneo, in his tantum rebus quae sole siccari possunt) that can be carried out into the sun, but in ch. xxv. of the more or less contemporary third book of Heraclius (Vienna Quellenschriften, No. iv.) oil-paint may be dried either in the sun or by artificial heat. Heraclius, moreover, knows how to mix dryers (oxide of lead) with his oil, a device with which Theophilus is not acquainted. Hence to the latter the defect of the medium was its slow drying, and Theophilus recommends as a quicker process the gum tempera already described. In any case, whether the painting be in oil or tempera, the finished panel must be varnished in the sun with " vernition " (ch. xxi.), a varnish compounded by heat of linseed oil and a gum, which is probably sandarac resin. The Mount Athos Handbook, § 53, describes practically the same technique, but indicates it as specially used for flesh, the inference being that the draperies were painted in tempera or with wax. It is worth noting that the well-known " black Madonnas," common in Italy as well as in the lands of the Greek Church, may be thus explained. They are Byzantine icons in which the flesh has been painted in oil and the draperies in another technique. The oil has darkened with age, while the tempera parts have remained in contrast comparatively fresh. Some of them are probably the earliest oil paintings extant. Oil painting accordingly, though in an unsatisfactory form,is established at least as early as A.D. 1100. What had been its previous history? Here it is necessary to take note of the interesting suggestion of Berger, that it was gradually evolved in the early Christian centuries from the then declining encaustic technique of classical times. We learn from Dioscorides, who dates rather later than the time of Augustus, that resin was mixed with wax for the painting of ships, and when drying oils came into use they would make with wax and resin a medium requiring less heat to make it fluid than wax alone, and one therefore more convenient for the brush-form of encaustic. Berger suspects the presence of such a medium in some of the mummy-case portraits, and points for confirmation to the chemical analysis of some pigments found in the grave of a painter at Herne St Hubert in Belgium of about the time of Constantine the Great (i. and ii. 230 seq.). One part wax with two to three parts drying (nut) oil he finds by experiment a serviceable medium. Out of this changing wax-technique he thinks there proceeded the use of drying oils and resins as media in independence of wax. If we hesitate in the meantime to regard this as more than a hypothesis, it is yet worthy of attention, for any hypothesis that suggests a plausible connexion between phenomena the origin and relations of which are so obscure deserves a friendly reception. The Trattato of Cennino Cennini represents two or three centuries of advance on the Schedula of Theophilus, and about contemporary with it is the so-called Strassburg MS., which gives a view of German practice just as the Trattato does of Italian. This MS., attention to which was first called by Eastlake (Materials, i. 126 seq.), contains a remarkable recipe for preparing " oil for the colours." Linseed or hempseed or old nut oil is to be boiled with certain dryers, of which white copperas (sulphate of zinc) is one. This, when bleached in the sun, " will acquire a thick consistence, and also become as transparent as a fine crystal. And this oil dries very fast, and makes all colours beautifully clear and glossy besides. All painters are not acquainted with it: from its excellence it is called oleum preciosum, since half an ounce is well worth a shilling, and with this oil all colours are to be ground and tempered," while as a final process a few drops of varnish are to be added. The MS. probably dates rather before than after 1400. Cennino's treatise, written a little later, gives avowedly the recipes and processes traditional in the school of Giotto throughout the 14th century. He begins his account of oil painting with the remark that it was an art much practised by the " Germans," thus bearing out what was said at the commencement of this section. He proceeds (chs. 90–94) to describe an oil technique for walls and for panels that sounds quite effective and modern. Linseed oil is to be bleached in the sun and mixed with liquid varnish in the proportion of an ounce of varnish to a pound of oil, and in this medium all colours are to be ground. " When you would paint a drapery with the three gradations," Cennino proceeds, " divide the tints and place them each in its position with your brush of squirrel hair, fusing one colour with another so that the pigments are thickly laid. Then wait certain days, come again and see how the paint covers, and repaint where needful. And in this way paint flesh or anything you please, and likewise mountains, trees and anything else." In other chapters Cennino recommends certain portions of a painting in tempera to be put in in oil, and nowhere does he give a hint that the work in oil gave any trouble through its unwillingness to dry. His medium appears, however, to have been thick, and perhaps somewhat viscous (ch. 92). This combination of oil paint and tempera on the same piece is a matter, as we shall presently see, of some significance. In the De re aedificatoria of L. B. Alberti (written about 1450), vi. 9, there is a mention of " a new discovery of laying on colours with oil of linseed so that they resist for ever all injuries from weather and climate," which may have some reference to so-called " German " practice. The next Italian writer who says anything to the purpose is Filarete, who wrote a long treatise on architecture and the arts of design about 1464. It is published in the Vienna Quellenschriften, neue Folge, No. III. Like Cennino, Filarete (loc. cit. p. 641) speaks of oil painting as specially practised in " Germany," and says it is a fine art when anyone knows how to compass it. The medium is oil of linseed. " But is not this very thick?" he imagines some one objecting. " Yes, but there is a way of thinning it; I do not quite know how; but it will be stood out in a vessel and clarify itself. I understand however that there is a quicker way of managing this—but let this pass, and let us go on to the method of painting." Filarete's evident uncertainty about a process, which may be that of the Strassburg MS. for producing oleum preciosum, and his reference to " Germany," inclines us to look elsewhere than to Italy for knowledge about the oil technique. ' As a fact the evidence of the recipe books is borne out remarkably by that of other records which show that a great deal of oil painting of one kind or another went on in northern lands from the 13th century onwards. These records are partly in the form of accounts, showing large quantities of oil and resins furnished for the use of painters engaged in extensive works of decoration; and partly in the form of contracts for executing pictures " in good oil colours." It is true that oil might be merely employed in mordants for gilding or in varnishes, and for oil painting merely in house-decorator fashion over wood, or for colouring statues and reliefs in stone; nevertheless, with a use of proper critical methods, it has been possible for M. Dalbon and others to establish incontestably the employment in artistic wall and panel-painting of drying oils and varnishes before the 15th century, both north and, to a lesser extent, south of the Alps. These passages have been too often quoted to be cited here. (See Eastlake, Materials, p. 46 seq.; Berger, Beitrdge iii. 206 seq., &c.) The earliest of the accounts, an English one, is dated r 239: " The king (Henry III.) to his treasurer and chamberlains. Pay from our treasury to Odo the goldsmith and Edward his son one hundred and seven-teen shillings and tenpence for oil, sandarac resin, and colours bought, and for pictures executed in the Queen's Chamber at Westminster." Another, about 1275 (temp. Edward I.) runs: " To Robert King, for one cartload of charcoal for drying the painting in the King's Chamber, IIIs VIIld." In Flanders in 1304 there is an account (Dalbon, p. 43) : " Pour zo los d'oile acatee pour faire destrempe as couleurs," in 1373-1374 one for XIII libvres d'olle de linnis d faire couleurs " (p. 45). This was for the use of a certain painter Loys, who executed mural compositions of which some of the subjects are recorded. In the matter of contracts, Dalbon (p. 52) prints one of 1320 pre-scribing figure and landscape subjects, to be executed " en la meilleur maniere que it pourront estre faites en painture," and concluding, " et seront toutes ces choses faites a huille," and he points convincingly to such wording as a proof that the work here under consideration must be regarded as artistic figure-painting and not mere house decoration. Lastly, just before 1400, the painter Jehan Malouel receives in 1399 oil with colours for " la peinture de plusieurs tables et tableaux d'autel," for the Carthusian convent of Champmol near Dijon, which proves the use of oil for panel as well as for mural painting. The further question about the survival of actual remains of work of the class just noticed is a very difficult one. There seems no reason why all this mural and panel work in oil of the 14th century should have perished, unless the medium was faulty, and, as is natural, many attempts have been made to identify extant examples as representing these early phases of the oil technique. Mural work we need not perhaps expect to find, for we know from the later experience of the Italians of the 16th century that it was difficult even then to find a safe method for oil painting on plaster. With panels preservation would be more likely, and it is always possible that some datable work of the kind may be identified that will carry the monumental history of oil painting back into the 14th century. An exhibition of early English painted panels was held in 1896 in the rooms of the Society of Antiquaries of London, and some good judges believed at the time that certain 14th-century panels from St Michael at Plea, Norwich, were in oil, but this cannot be regarded as established. If such then be the early history of oil painting, what attitude are we to adopt in face of the famous statement by Vasari that the technique was the invention of the Flemish painter Van Eyck in the year 1410? The statement was first made in the 21st chapter of Vasari's Introduction to his Lives of the Artists (1550), and runs as follows: " Fu una bellissima inventione, ed un gran' commoditd all' arte della pittura, it trovare it colorito a olio. Di the fu prima inventore in Fiandra Giovanni da Bruggia (Jan van Eyck). In the life of Antonello da Messina, in the same edition, Vasari dresses up the bare fact he here relates, and gives it the personal anecdotal turn that accords with his literary methods. Here the " invention " follows on the incident of the splitting of a tempera panel varnished in oil, that according to traditional practice Van Eyck had put out in the sun to dry. This artist then turned his attention to devising some means for avoiding such mischances for the future, and, in Vasari's words, " being not less dissatisfied with the varnish than with the process of tempera painting, he began to devise means for preparing a kind of varnish which should dry in the shade, so as to avoid having to place his pictures in the sun. Having made experiments with many things both pure and mixed together, he at last found that linseed and nut oil, among the many which he had tested, were more drying than all the rest. These, therefore, boiled with other mixtures of his, made him the varnish which he had long desired." This varnish Vasari goes on to say he mixed with the colours and found that it " lit up the colours so powerfully that it gave a gloss of itself," without any after-coat of varnish. Such is the famous passage in Vasari that has probably given rise to more controversy than any similar statement in the literature of the arts. The question is, in what did the invention " of the Van Eycks, Hubert and Jan his younger brother, consist? and the first answer that would occur to anyone knowing alike the earlier history of the oil medium and Vasari's anecdotal predilections is the answer " There was no invention at all." The drying properties of linseed and nut oil and the way to increase these had long been known, as had also the preparation of sandarac oil-varnish, as well as a colourless (spirit?) varnish of which there is mention in accounts prior to the 15th century (Dalbon, p. 93). The mixing of varnish with oil for a medium was also known, and indeed the oleum preciosum may be the real " invention " of which Alberti and Filarete had only vaguely heard, and of which the Van Eycks later on received the credit. The epitaphs for the tombs of the two Van Eycks make no mention of such a feat as Vasari ascribes to them, and it is quite open to anyone to take up the position that it was no improvement in technique that brought to the Van Eycks their fame in connexion with oil painting, but rather an artistic improvement that consisted in using a traditional process to execute pictures which in design, finish, beauty and glow of colour far surpassed every-thing previously produced in the northern schools. Pliny writes of the works of a Greek painter of about 400 B.C. that they were the first that had the power " to rivet the gaze of the spectator," and in like manner we may say of the " Adoration of the Lamb " by the Van Eycks, the titular firstfruits of the oil painter's technique, that it impressed the world of its time so mightily through its artistic power and beauty as to elevate to a sort of mystic importance the very method in which the paints were mixed. There is much force in this view, but at the same time it is impossible to deny to the Van Eycks the credit of technical improvements. For one thing, an artist who has an exceptional feeling for colour, texture and delicacy of finish will certainly pay special attention to his technical media; for another, the Van Eycks had a reputation long before Vasari's time for researches into these media. In 1456, fifteen years after the death of the younger brother, Bartolommeo Facio, of Spezzia, wrote a tract De viris illustribus in which he speaks of a certain " Joannus Gallicus," who can be identified as Jan van Eyck, as specially " learned in those arts which contributed to the making of a picture, and was on that account credited with the discovery of many things in the properties of colours, which he had learned from ancient traditions recorded by Pliny and other writers." Filarete (c. 1464) also knew of the repute of Jan van Eyck in connexion with the oil technique. Hence we may credit the Van Eycks with certain technical improvements on traditional practices and preparations in the oil technique, though these can hardly be termed " inventions," while their artistic achievement was great enough to force into prominence whatever in the technical department they had accomplished. Another and a more important question remains behind: What was, in fact, the practice in the matter of oil painting in vogue before the Van Eycks, altered or at any rate perfected by them and their successors, and in general use up to the time of Vasari; and how was it related to the older more widely diffused painting " a tempera " ? It is indisputable that the oil painting of the Van Eycks and the early Flemish school, together with that of the Florentines and Umbrians, and indeed of all the Italians up to Vasari's time, save the Venetians, Correggio, and some other north Italians, does not greatly differ in artistic effect, nor, as far as can be judged, in handling, from earlier or contemporary temperas. For example, at Venice in the 15th century, Crivelli paints always in tempera, Cima in oils, but the character of their surface is almost the same, and if anything the tempera is richer in effect than the oil. The contrary is no doubt the case with the tempera " Madonna with the Violet " in the Priests' Seminary at Cologne when compared with the somewhat later. " Dombild," also by Stephan Lochner, which is believed to be painted in oils, but the two are still in technical character very nearly akin. The fact is that tempera panels were usually coated with an oil varnish, necessarily of a somewhat warm tint, and we could hardly expect to distinguish them from oil pictures painted in or covered by varnish, unless there were a difference in the handling of the pigments. The method of handling appears however to be on the whole the same, and there are many who believe that in all essentials it is the same. Tempera panels, as we have learned from Cennino, were not only varnished but in parts might be painted in oils (ch. 143), and it is one view of the technique of the early Flemings that it was only an over-painting in oils over a preparation in tempera. Berger is of the opinion that the process was something between the two, that is to say, that it was oil tempera, the medium being an emulsion of oil and water through the intermediary of a gum. Such a medium would, as he points out (Beitrage, iii. 247 seq.), combine the thinness and limpidity in manipulation characteristic of a water tempera with the property of drying hard and impervious to moisture. This is of course only a theory. Of far more weight is the suggestion made by Principal Laurie, of Edinburgh, who has carried on for years a series of careful experiments in the various pigments and media employed in oil painting. As one result of these experiments he has found that the ordinary drying oils and oil varnishes do not, as used to be assumed, " lock up " or completely cover and protect pigments so as to prevent the access of moisture and the gases of the atmosphere, but that this function is far more effectively performed by hard pine-balsams, such as Canada balsam, dissolved in an essential oil and so made into a varnish or painting medium. In pictures by Van Eyck Principal Laurie has detected what he believes to be the use of pigments of a notoriously fugitive character, and he is convinced that the most effectual medium for preserving these in the condition in which they have come down to us would be a natural pine-balsam, with probably a small proportion of drying oil; he suggests therefore that the introduction of these ingredients maybe the real secret of the Van Eyck technique. There is as yet no proof that the Van Eycks really used such a medium, though it is a preparation possible at their time, and when thinned by a process of emulsification with egg, as Dr Laurie suggests, would be a serviceable one; but they and the other early oil painters certainly used a method, and in all probability media, that did not differ greatly as regards manipulation from those in vogue in tempera. From the aesthetic point of view therefore we have to regard early oil painting as only another form of the older tempera,expressing exactly the same artistic ideals and dominated by the same view of the relation of art to nature. To Vasari the artistic advantage of the oil medium was, first, its convenience, and, next, the depth and brilliancy it lent to the colours, which he says it " kindled," while at the same time it lent itself to a soft fusing of tints in manipulation, so that artists could give to their figures in this technique the greatest charm and beauty combined with a force that made them seem to stand out in relief from the panel, Such a description applies very justly to work like that of the Van Eycks in the " Adoration of the Lamb," or the later panels of Antonello da Messina, who, according to Vasari's often-repeated story, introduced the Flemish system of oil-painting into Venice. The description does not however apply to the freer, more sweeping, more passionate handling of the brush by the greatest of the Venetians such as Titian or Veronese, and still less to the oil painting of 17th-century masters like Rubens or Rembrandt or Velazquez. It is quite clear that whatever improvements in oil technique were due to the early Flemings, oil painting in the modern sense owes still more to the Venetians, who first taught the world the full artistic possibilities of the process. Giovanni Bellini, whose noble altarpiece in S. Pietro at Murano may be called, in a phrase once applied to another of his pictures, " the canon of Venetian art," is probably entitled to be called the father of modern oil painting. Beginning as a painter in tempera and adopting the new process about 1475, Bellini was able so far to master the new medium that he handed it on with all its possibilities indicated to Giorgione, Palma and Titian. That Venetian oil painting however,with all its brilliancy and freedom, was a child of the older tempera technique is shown by its characteristic method, which consisted in an under-painting in dead colour, over which were superimposed the transparent glazes that secured the characteristic Venetian richness of colouring. Now all the recent writers on the Van Eyck technique agree that, whatever were the exact media employed, the tempera tradition, and perhaps the tempera vehicles, were maintained for the underpainting. In the old tempera-panel technique of Cennino there was a monochrome underpainting in a greenish pigment, over which the flesh tints were spread in thin layers so as never completely to obliterate the ground. Such an under-painting in a few simple colours, black, white and red, was employed by Titian and others of the Venetians, and over it were laid the rich juicy transparent pigments, till " little by little he would have covered with real living flesh these first abstracts of his intention " (Boschini). There is some evidence that in many cases these underpaintings were in tempera, which would have the advantage of drying more quickly than under-paintings in oil, and Boschini (Le Ricche minere della pittura veneziana, 1674) expressly says that the blues in Venetian paintings, e.g. by Veronese, were painted often a guazzo. There was a reason, however, why the Venetians would alter the traditional practice of the Flemish forerunners. The latter were almost entirely panel painters, while the Venetians used canvas. Now certain media, like the hard pine-balsams which Dr Laurie thinks were the basis of the Van Eyck medium, are suitable for the immovable surfaces of a well-grounded panel, but would be liable to crack on canvas which is more or less yielding. Hence the tougher oil vehicles were in advanced Venetian painting exclusively employed. This distinction between the thin transparent pigments and those of an opaque body, which is as old as oil painting in any form, becomes in the hands of Bellini and the later Venetians the fundamental principle of the technique. The full advantage of this thinness and transparency is gained by the use of the pigments in question as " glazes " over a previously laid solid impasto. This impasto may be modelled up in monochrome or in any desired tints chosen to work in with the colours of the superimposed glazes. Effects of colour of great depth and brilliancy may thus be obtained, and after the glaze has been floated over the surface a touch of the thumb, where the underpainting is loaded and lights are required, will so far thin it as to let the underlying colour show through and blend with the deeper tint of the glaze in the shadows. Thus in the noble Veronese in the London National Gallery, called the " Consecration of St Nicholas," the kneeling figure of the saint is robed in green with sleeves of golden orange. This latter colour is evidently carried through as underpainting over the whole draped portions of the figure, the green being then floated over and so manipulated that the golden tint shows through in parts and gives the high lights on the folds. Again the relation of the two kinds of pigment may be reversed, and the full-bodied ones mixed with white may be struck into a previously laid transparent tint. The practice of painting into a wet glaze or rubbing was especially characteristic of the later Flemings, with Rubens at their head, and this again, though a polar opposite to that of the Venetians, is also derived from the earlier tempera, or modified tempera, techniques. The older tempera panels, when finished, were, as we have seen, covered with a coating of oil varnish generally of a warm golden hue, and in some parts they were, as Cennino tells us, glazed with trans-parent oil paint. Now Van Mander tells us in the introduction to his Schilderboek of 1604, verse 17, that the older Flemish and German oil painters, Van Eyck, Durer and others, were accustomed, over a slightly painted monochrome of water-colour in which the drawing was carefully made out, to lay a thin coat of semi-transparent flesh tint in oil, through which the under-painting was still visible, and to use this as the ground for their subsequent operations. In the fully matured practice of Rubens this thin glaze became a complete painting of the shadows in rubbings of deep rich transparent oily pigment, into which the half-tones and the lights were painted while it was still wet. Descamps, in his Vie des peintres flamands (Paris, 1753),describes Rubens's method of laying in his shadows without any use of white, which he called the poison of this part of the picture, and then painting into them with solid pigment to secure modelling by touches laid boldly side by side, and afterwards tenderly fused by the brush. Over this preparation the artist would return with the few decided strokes which are the distinctive signs-manual of the great master. The characteristic advantages of this method of work are, first, breadth, and second, speed. The under tint, often of a rich soft umber or brown, being spread equally over the canvas makes its presence felt throughout, although all sorts of colours and textures may be painted into it. Hence the whole preserves a unity of effect that is highly pictorial. Further, as the whole beauty of the work depends on the skill of hand by which the solid pigment is partly sunk into the glaze at the shadow side, while it comes out drier and stronger in the lights, and as this must be done rightly at once or not at all, the process under a hand like that of Rubens is a singularly rapid one. Exquisite are the effects thus gained when the under tint is allowed to peep through here and there, blending with the solid touches to produce the subtlest effects of tone and colour. Of these two distinct and indeed contrasted methods of handling oil pigment, with solid or with transparent under-painting, that of the Flemings has had most effect on later practice. The technique dominated on the whole the French school of the 18th century, and has had a good deal of influence on the painting of Scotland. In general, however, the oil painting of the 17th and succeeding centuries has not been bound by any distinctive rules and methods. Artists have felt themselves free, perhaps to an undue extent, in their choice of media, and it must be admitted that very good results have been achieved by the use of the simplest vehicles that have been known throughout the whole history of the art. If Rembrandt begins in the Flemish technique, Velazquez uses at first solid under-paintings of a somewhat heavy kind, but when these masters attain to full command of their media they paint apparently without any special system, obtaining the results they desired, now by one process and now again by another, but always working in a free untrammelled spirit, and treating the materials in the spirit of a master rather than of a slave. In modern painting generally we can no longer speak of established processes and methods of work, for every artist claims the right to experiment at his will, and to produce his result in the way that suitshis own individuality and the special nature of the task before him. § 45. Water - Colour Painting.—(Cosmo Monkhouse, The Earlier English Water-Colour Painters, and ed., London, 1897; Redgrave, A Century of Painters; and Hamerton, The Graphic Arts, contain chapters on this subject.) Water-colour painting, as has been said, is only a particular form of tempera, in which the pigments are mixed with gum to make them adhere, and often with honey or glycerin to prevent them drying too fast. The surface operated on is for the most part paper, though " miniature " painting is in water-colour on ivory. The technique was in use for the illustrated papyrus rolls in ancient Egypt, and the illuminated MSS. of the medieval period. As a rule the pigments used in the MSS. were mixed with white and were opaque or " body " colours, while water-colour painting in the modern sense is mostly trans-parent, though the body-colour technique is also employed. There is no historical connexion between the water-colour painting on the vellum of medieval MSS. and the modern practice. Modern water-colour painting is a development rather from the drawings, which the painters from the 15th to the 17th century were constantly executing in the most varied media. Among the processes employed was the reinforcement of an outline drawing with the pen by means of a slight wash of the same colour, generally a brown. In these so-called pen-andwash drawings artists like Rembrandt were fond of recording their impressions of nature, and the water-colour picture was evolved through the gradual development in importance of the wash as distinct from the line, and by the gradual addition to it of colour. It is true that we find some of the old masters occasionally executing fully-tinted water-colour drawings quite in a modern spirit. There are landscape studies in body-colour of this kind by Durer and by Rubens. These are, however, of the nature of accidents, and the real development of the technique did not begin till the 18th century, when it was worked out, for the most part in England, by artists of whom the most important were Paul Sandby and John Robert Cozens, who flourished during the latter half of the 18th century. First the wash, which had been originally quite flat, and a mere adjunct to the pen outline, received a certain amount of modelling, and the advance was quickly made to a complete monochrome in which the firm outline still played an important part. The element of colour was first introduced in the form of neutral tints, a transparent wash of cool grey being used for the sky and distance, and a comparatively warm tint of brown for the foreground. " The progress of English water-colour," writes Mr Monkhouse, " was from monochrome through neutral tint to full colour." Cozens produced some beautiful atmospheric effects with these neutral tints, though the rendering of nature was only conventional, but it was reserved for the second generation of English water-colour artists to develop the full resources of the technique. This generation is represented centrally by Thomas Girtin (1775–18o2) and J. M. W. Turner (1775–1851), the latter of whom is by far the greatest representative of the art that has hitherto appeared. To Girtin, who died young and whose genius, like that of Masaccio, developed early, is due the distinction of creating water-colour painting as an art dealing with the tones and colours of nature as they had been dealt with in the older media. W. H. Pyne, a contemporary water-colour artist who also wrote on the art, says of Girtin that he " prepared his drawings on the same principle which had hitherto been confined to painting in oil, namely, laying in the object upon his paper with the local colour, and shading the same with the individual tint of its own shadow. Previous to the practice of Turner and Girtin, drawings were shaded first entirely through, whatever their component parts—houses, cattle, trees, mountains, foregrounds, middle-ground and distances, all with black or grey, and these objects were after-wards stained or tinted, enriched or finished, as is now the custom to colour prints. It was the new practice, introduced by these distinguished artists, that acquired for designs in water-colours upon paper the title of paintings." Girtin " opened the gates of the art " and Turner entered in. If the palette of the former was still restricted, Turner exhausted all the resources of the colour box, and moreover enriched the art by adding to the traditional transparent washes the effects to be gained from the use of body colour. Body colours, how-ever, were not only laid on by Turner with the solid impasto of the medieval illuminations. He was an adept at dragging thin films of them over a tinted ground so as to secure the subtle colour effects which can also be won in pastel. It would be useless to attempt any account of the technical methods of Turner or of the more modern practitioners in the art, for as in modern oil painting so here, each artist feels at liberty to adopt any media and processes which seem to promise the result he has in view. The varieties of paper used in modern water-colour practice are very numerous, and the idiosyncrasy of each artist expresses itself in the way he will manipulate his ground; superinduce one over the other his transparent washes; load with solid body colour; sponge or scratch the paper, or adopt any of the hundred devices in which modern practice of painting is so rife. (G. B. B.)
End of Article: PART III

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