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LITHOGRAPHY (Gr. MOOS, a See also: process of See also: drawing or .laying down a design or transfer, on a specially prepared See also: stone or other suitable
See also: surface, in such a way that impressions may be taken therefrom
.
The principle on which lithography is based is the antagonism of grease and See also: water
.
A chemically pure surface having been secured on some substance that has an equal See also: affinity for both grease and water, in a method hereafter to be described, the parts intended to See also: print are covered with an unctuous composition and the rest of the surface is moistened, so that when a greasy See also: roller is applied, the portion that is wet resists the grease and that in which an affinity for grease has been set up readily accepts it; and from the surface thus treated it will be seen that it is an easy thing to secure an impression on paper or other material by applying suitable pressure
.
The inventor of lithography was Alois See also: Senefelder (1771–1834); and it is remarkable what a grip he at once seemed to get of his invention, for whereas the invention of printing seems almost a See also: matter of See also: evolution, lithography seems to come upon the scene fully equipped for the See also: battle of See also: life, so that it would be a bold craftsman at the See also: present See also: day who would affirm that he knew more of the principles underlying his See also: trade than Senefelder (q.v.) did within See also: thirty years of its invention
.
Of course practice has led to dexterity, and the See also: great See also: volume of trade has induced many See also: mechanical improvements and facilities, but the principles have not been taken any further, while some valuable methods
have been allowed to fall into desuetude and would well repay some experimentally disposed See also: person to revive
.
Lithography may be divided into two See also: main branches—that which is See also: drawn with a greasy crayon (rather illogically called " See also: chalk ") on a grained stone, and that which is drawn in " ink " on a polished stone
.
Whatever may be thought in regard to the See also: original See also: work of the artists of various countries who have used lithography as a means of expression, there can be little doubt that in the_ former method the See also: English professed lithographer has always held the pre-See also: eminence, while French, See also: German and See also: American artists have surpassed them in the latter
.
Chalk lithography subdivides itself into work in which the black predominates, although it may be supported by 5 or 6 shades of modified colour—this branch is known as "black and tint " work—and that in which the black is only used locally like any other colour
.
Frequently this latter class of work will require a dozen or more See also: colours, while some of the finest examples have had some twenty to thirty stones employed in them
.
Work of this description is known as chromo-lithography
.
Each colour requires a See also: separate stone, and work of the highest quality may want two or three blues with yellows, reds, greys and browns in proportion, if it is desired to secure a result that is an approximate rendering of the original See also: painting or drawing
.
The question may perhaps be asked: " If the well-known three-colour process" (see PROCESS) " can give the full result of the artist's palette, why should it take so many more colours in lithography to secure the same result?" The answer is that the stone practically gives but three gradations—the solid, the See also: half tint and the quarter tint, so that the combination of three very carefully prepared stones will give a very limited number of combinations, while a moderate estimate of the shades on a toned See also: block would be six; so that a very See also: simple mathematical problem will show the far greater number of combinations that the three blocks will give
.
Beyond this, the chromolithographer has to exercise very great See also: powers of colour analysis; but the human mind is quite unable to See also: settle offhand the exact proportion of red, blue and yellow necessary to produce some particular class say of See also: grey, and this the camera with the aid of colour filters does with almost perfect precision
.
Notwithstanding these disadvantages, lithography has these strong points: (r) its utility for small See also: editions on account of its, at present, smaller See also: prime cost; (2) its suitability for subjects of large See also: size; (3) its superiority for subjects with outlines, for in such cases the outline can be done in one colour, whereas to secure this effect by the admixture of the three colours requires marvellously See also: good See also: registration, the See also: absence of which would produce a very large proportion of " waste " or faulty copies; (4) capacity for printing on almost any paper, whereas, at the See also: time of writing, the tri-colour process is almost entirely limited to printing on coated papers that are very heavy and not very enduring
.
With regard to the two branches of chalk lithography, the firms that maintained the English supremacy for black and tint work in the early days were Hulemandel, Day and Haghe and See also: Maclure, while the best chromo-lithographic work in the same See also: period was done by Vincent Brooks, the See also: brothers Hanhart, See also: Thomas Kell and F
.
Kell
.
In reference to the
See also: personal work of professed lithographers during the same period, the names of See also: Louis Haghe, J
.
D
.
Harding, J
.
Needham, C
.
Baugniet, L
.
Ghemar,
See also: William
See also: Simpson, R
.
J
.
Lane, J
.
H . See also: Lynch, A
.
Maclure and Rimanozcy stand for black and tint work; while in chromolithography J
.
M
.
Carrick, C
.
Risdon, William Bunney, W
.
Long, See also: Samuel Hodson, Edwin Buckman and J
.
See also: Lewis have been conspicuous among those who have maintained the See also: standard of their craft
.
In the foregoing See also: list will be recognized the names of several who have had admirable See also: works on the walls of the Royal See also: Academy and other exhibitions; Mr Lane, who exhibited lithographs from 1824 to 1872, was for many years the See also: doyen of lithographers, and the only one of their number to attain See also: academic See also: rank, but Lynch and See also: John Cardwell
See also: Bacon were his pupils, and Bacon's son, the painter John H
.
F
.
.Bacon, was electedto the Royal Academy in 1903
.
In the first
See also: decade of the loth century the number of firms doing high-class work, and the artists who aided them in doing it, were more numerous than ever, and scarcely less able, but it would be outside the present purpose to differentiate between them
.
The raison d' are of " stipple " work is its capacity for re-transferring without serious loss of quality, for it can scarcely be contended that it is as See also: artistic as the methods just described
.
Retransferring is the process of pulling impressions from the original stones with a view to making up a large See also: sheet of one or more small subjects, or where it is desired to print a very large number without deterioration of the original or See also: matrix stone
.
The higher class work in this direction has been done in See also: France, See also: Germany and the See also: United States, where for many years superiority has been shown in regard to the excellence and rapidity of retransferring
.
To this cause may be attributed the fact that the box tops and See also: Christmas See also: cards on the English market were so largely done abroad until quite See also: recent times
.
The work of producing even a small face in the finest See also: hand stipple is a lengthy and tedious affair, and the English craftsman has seldom shown the See also: patience necessary for this work; but since the American invention known as See also: Ben Day's shading See also: medium was introduced into See also: England the trade has largely taken it up, and thereby much of the tedium has been avoided, so that it has been found possible by its means to introduce a freedom into stipple work that had not before been found possible, and a very much better class of work has since been produced in this department
.
About the See also: year 1868 grained paper was invented by Maclure, See also: Macdonald & Co
.
This method consists in impressing on ordinary Scotch transfer or other suitable paper a grain closely allied to that of the lithographic stone
.
It appears to have been rather an improvement than a new invention, for drawing paper and even See also: canvas had been coated previously with a material that adhered to a stone and See also: left on the stone the greasy drawing that had been placed thereon; but still from this to the beautifully prepared paper that was placed on the market by the See also: firm of which the See also: late Andrew Maclure was the See also: head was a great advance, and although the first use was by the ordinary craftsman it was not long before artists of eminence saw that a new and convenient mode of expression was opened up to them
.
On the first introduction of lithography the artists of every nation hastened to avail themselves of it, but soon the cumbrous character of the stone, and the fact that their subjects had to be drawn backwards in See also: order that they might appear correctly on the paper, wore down their newly-See also: born zeal, and it was only when the grained paper See also: system was perfected, by which they could make their drawings in the comfort of their studios without See also: reversing, that any serious revival took place
.
Although excellent work on grained paper had been done by Andrew Maclure, Rimanozcy, John Cardwell Bacon, Rudofsky and other crafts-men, the See also: credit for its furtherance among artists must be given to Thomas Way and his son T
.
R
.
Way, who did much valuable See also: pioneer work in this direction
.
The adhesion of such artists of eminence asSee also: Whistler, See also: Legros, See also: Frank See also: Short, See also: Charles Shannon, Fantin Latour, William
See also: Strang, Will Rothenstein, See also: Herbert Railton and See also: Joseph See also: Pennell, did not a little to aid lithography in resisting the encroachments of other methods into what may still be considered its sphere
.
As a means of reproducing effects which an artist would otherwise get by pencil or crayon, it remains entirely unequalled, and it is of obvious See also: advantage to See also: art that twenty-five or fifty copies of an original work should exist, which, without the aid of lithography, might have only been represented by a single sketch, perhaps stowed away among the possessions of one private See also: collector
.
In regard to grained paper work, undue stress has often been placed upon the rapid deterioration of the stone, some contending that only a few dozen first-class proofs can be taken; this has led to the feeling that it is unsuited to See also: book See also: illustration, and damage has been done to the trade of lithography thereby
.
It may be mentioned that quite recently about too auto-lithographs in black and three colours, the combined work of Mr and
Mrs Herbert Railton, have been treated by the Eberle system used, and the operation is known as " passing," while the plates are of See also: etching described below, and although an infinitesimal loss
of quality may have arisen, such as occurs when a copper etching is See also: steel faced, some 2000 to 3000 copies were printed without further deterioration, and an edition of vignetted sketches was secured, far in advance of anything that could have been attained from the usual screen or half-toned blocks
.
Grained paper is much used in the ordinary lithographic studio for work such as the See also: hill shading of maps that can be done without much working up, but the velvety effects that in the hands of Louis Haghe and his contemporaries were so conspicuous, cannot be secured by this method
.
The effects referred to were obtained by much patient work of a " tinter," who practically laid a ground on which the more experienced and artistic craftsman did his work either by scraping or accentuation
.
Where
See also: fine See also: rich blacks are needed, artists will do well to read the notes on the " aqua-tint " and " See also: wash " methods described by Senefelder in his well-known See also: treatise, and afterwards practised with great skill by Hulemandel
.
Lithography is of great service in educational matters, as its use for diagrams, See also: wall pictures and maps is very general; nor does the influence end with schooldays, for in the See also: form of pictures at a moderate price it brings art into homes and lives that need brightening, and even in the form of posters on the much-abused hoardings does something for those who have to spend much of their time in the streets of great cities
.
According to the census of 1901, 14,686 See also: people in the United See also: Kingdom found their occupation within the trade, while according to a Home Office return (1906), 20,367 persons other than lithographic printers were employed by the firms carrying on the business
.
As it may be assumed that an equal number are employed in France, Germany, the United States of See also: America and the See also: world at large, it is clear that a vast See also: industrial army is employed in a trade that, like letterpress printing, has a very beneficial influence upon those engaged in it
.
Technical Details.—The following description of the various methods of lithography is such as may be considered of See also: interest to the general reader, but the serious student who will require formulas and more precise directions will do well to consult one of the numerous text-books on the subject
.
Stone and Stone Substitutes.—The quality of stone first used by Alois Senefelder, and discovered by him at the See also: village of Solenhofen in See also: Bavaria, still remains unsurpassed
.
This deposit, which covers a very largeSee also: area and underlies the villages of Solenhofen, Moernsheim and Langenaltheim, has often been described, sometimes for interested motives, as nearly exhausted; but a visit in 1906 revealed that the output—considerable as it had been during a period little short of a century—was very unimportant when compared to the great mass of carbonaceous See also: limestone existing in the neighbourhood
.
The strong point in favour of this source of supply, in addition to its unrivalled quality, is the evenness of its stratification, and the fact that after the removal of the surface deposits, which are very thin, the stones come out of large size, in thickness of 3 to 5 in., and thus just suited for lithographic purposes and needing only to be wrought in the vertical direction
.
Other deposits of suitable stone have been fcund in France, See also: Spain, See also: Italy and See also: Greece, but transit and the absence of suitable stratification have restricted them to little more than See also: local use
.
Beyond this, few of the deposits other than in the neighbourhood of Solenhofen have been of the exact degree of See also: density necessary, and the heavier varieties do not receive the grease with sufficient readiness
.
The See also: desire to find other See also: sources of supply has been stimulated by the social conditions existing in See also: southern Bavaria, for the quarries are largely owned by peasant proprietors, who have very well-defined business habits of their own which make transactions difficult
.
Among other things, they will seldom supply the highest grades and the largest sizes to those who will not take their proportion of See also: lower quality and smaller sizes; and this, in view of the very expensive transit down the Rhine to See also: Rotterdam, with a railway journey at one end and a See also: sea journey at the other, is a source of difficulty to the importer in other countries
.
The earliest substitute for lithographic stone was See also: zinc, which has been used from early days and is now more in demand than ever; it requires very careful printing as the grease only penetrates the material to a very slight extent, and the same must be said in regard to the water
.
From this cause, when not in experienced hands, trouble is likely to arise; and when this has occurred, remedial methods are much more difficult than with stones
.
When put away for storage, a dry place is very essential, as corrosion is easily,set up
.
At first the plates were quite thick, and almost invariably grained by a zinc " mailer " and acid; now a See also: bath of acid is more generallyquite thin, which renders them suitable for bending round the cylinders of rotary See also: machines
.
So far we have been dealing with plain zinc, but variations are caused, either by the oxidization of the surface or by coating the See also: plate with a composition closely allied to lithographic stone and applied in a form of semi-solution
.
This class of plate was first invented by Messrs C
.
& E . Layton, and a modification was invented by Messrs Wezel and Naumann ofSee also: Leipzig, who brought its use to a high See also: pitch of perfection for transferred work such as Christmas cards
.
A treatment of iron plates by exposing them to a high temperature has recently been patented, and has had some measure of success, while the See also: Parker printing plate, which is practically a sheet of zinc so treated as to secure greater porosity and freedom from oxidization, is rapidly securing a good position as a stone substitute
.
Preparation of the Stones.—In this department the cleanliness so necessary right through the lithographic process must be carefully observed, and a leading point is to secure a level surface and to ensure that the front and back of the stone are strictly parallel, i.e. that the stones stand the test of both the straight edge and the callipers
.
A good See also: plan to ensure evenness on the surface is to mark the front with two diagonal lines of some non-greasy substance till the top stone (which should not be too small, and should be constantly revolved on the larger one) has entirely removed them
.
The application of the straight edge from time to time will end in securing the desired flatness, on which so much of the future printing quality depends
.
The usual method is to rub out with See also: sand, and then rub with pumice and See also: polish with water of See also: Ayr or snake stone
.
For chalk work, the further work of graining has to be done by revolving a small stone See also: muller on the surface with exceedingly fine sand or powdered
See also: glass
.
Many appliances (some very expensive) have been devised for doing the See also: principal See also: part of this work by machine—none more effective than those methods by which a disk of about 12 in. is kept revolving on a See also: rod attached to the ceiling, guided by hand over all parts of the stone; but for large surfaces the ceiling needs to be rather high so as to allow of a long expanding rod reaching the surface at a moderate angle
.
When this machine is fitted with See also: friction disk driving, very wide variations of See also: speed are possible, and the machine can be driven so slowly and evenly as to secure a very See also: fair (but not first class) grain, in addition to speedy rubbing out, which is the chief aim of the apparatus
.
Preparing a Subject in Chalk or Chalk and Tints
.
This branch of work is much less in demand than formerly
.
A grey stone having been selected and finely grained with sand or powdered glass passed through a See also: sieve of 8o to 12o meshes to the lineal inch, and the artist having made his tracing, this tracing is reversed upon the stone with the interposition of a piece of paper coated with red chalk, and the chalk See also: side towards the surface; the lines on the tracing are then gone over with a tracing point, so that a See also: reproduction in red chalk is left upon the stone
.
It will then be desirable to secure a stock of pointed Lemercier chalks of at least two grades, hard and soft: the pointing is a matter that requires experience, and is done by the worker drawing a See also: sharp See also: pen-knife towards him in a slicing manner as though trying to put a point upon a piece of See also: cheese
.
Care should be taken that the falling pieces are gathered into a box, or they may do irreparable See also: mischief to the work
.
The work of outlining is done with No
.
1 or hard chalk, and until experience is gained it will be well to depend chiefly on this grade, securing rich dark effects by tinting or going over the stone in various directions and then See also: finishing with litho-graphic ink where absolute blacks are required
.
This ink (Vanhymbeck's or Lemercier's are two good makes) needs cargul preparation, the method being to warm a saucer and rub the ink dry upon it, then add a little distilled water and incorporate with the See also: finger
.
It is of great importance not to use any ink left over for the next day, but always to have a fresh daily supply
.
When the drawing is thus completed, it will require what is termed
etching, by which the parts intended to receive the printing ink, and
already protected by an acid-resisting grease, will be left above the
unprotected surface
.
The acid and gum mixture varies in accordance
with the quality of the work and the character of the stone
.
A
patiently executed specimen will, for instance, stand more etching
than a hastily drawn one; while a grey stone will require more of
the nitric acid than a yellow one
.
This is one of the most important
tasks that a lithographer has to perform
.
A proportion of 1.5 parts
of acid to too parts of a strong solution of gum arabic will be found
to be approximately what is required, but the exact proportion must
be settled by experience, a safe course being to See also: watch the See also: action that
occurs when a small quantity is placed on the unused margin of the
stone
.
Many put the etching mixture on with a flat camel-hairSee also: brush, which should be of good width to avoid streaks
.
The present
writer's own preference is to pour the mixture on to the stone when it
is in a slanting position; or it is perhaps better to have an etching
trough, a strong box lined with pitch, with bearers at the bottom to
prevent the stone coming in contact with it, and a hole through
which the diluted acid may pass away for subsequent use
.
The etch-
See also: ing is then done with acid and water poured over the stone while in a
sloping position, and the subsequent pouring of a solution of gum
arabic completes the preparation
.
The late Mr William Simpson,
whose See also: Crimean lithographs are well known, once stated at the
Society of Arts that in his opinion Mr Louis Haghe's reproduction
i6
of See also: David Robert's great picture of " The Taking of Jerusalem " was the most important piece of chalk lithography ever executed, and that he well remembered that it took two years to execute it, and that all the combined talent of Messrs Day & Haghe's establishment was utilized in its etching
.
He stated that, notwithstanding every precaution, it was under-etched, and that after half a dozen impressions the great beauty and brilliancy of the work had departed
.
This incident indicates sufficiently the serious nature of this part of the lithographer's work
.
If the chalk drawing has to have tints, it will be necessary to make as many dusted offsetts as there are colours to be used; in this class of work there are generally only two,—one warm or sandy shade and the other a quiet blue.—and these, with the black and the neutral colour secured by the superposition of the two shades, give an excellent result, of which Haghe's sketches in Belgium may be taken as a leading example
.
In making such subjects suitable for present-day printing in the machine, the paper will require to be of a good " rag " quality, See also: free from size and damped before printing
.
To secure accuracy of See also: register the paper must be kept in a See also: damp See also: cloth to prevent the edges drying, and other machines should be kept available for each of the tints so that all work printed in black in the See also: morning may be completed the same See also: night
.
In this way large editions might be printed of either original or retransferred work at prices rendering, the prints suitable for high-class magazines
.
Preparing a Chromo Lithograph.—For this purpose the proceedings will be much the same as those suggested for the black and tint work, but the preliminary tracing will be done in lithographic ink on tracing transfer paper or scratched on gelatine, the lines being subsequently filled in with transfer ink, and will be used as a " See also: key," a guide stone that will not be printed; and the number of stones necessary will probably be much more numerous
.
The initial point will be to consider if the work is to have the edition printed from it, or whether it has to be transferred after proving and before printing; generally speaking, large subjects such as diagrams or posters will be worked
See also: direct, while Christmas cards, postcards, handbills or labels, will he repeated many times on larger stones
.
For the former class a much wider range of methods is possible, but many of these are difficult to transfer, and the deterioration that arises makes it desirable to limit their use when transferring is contemplated . There-fore, chalk-rubbed tints, See also: varnish tints, stumping, wash, air brush, are the methods for original work, while work that has to be transferred is limited to ink work in See also: line or stipple on a polished stone with the aid of " mediums " as before described, and ink " spluttered " on to the stone from a tooth brush
.
It should be mentioned that work done on grained paper is more suitable for retransfer than ordinary chalk work, and so is often very useful when a chalk effect is desired from a polished stone
.
In proving, opaque colours will be got on first, and it will often be found a good plan to put the black on early, for it gives a good idea of how the work is proceeding, and the strength of the touches (for the black should generally be used sparingly) is often pleasantly softened by the semi-opaque colours which should come on next
.
It is desirable to pull impressions of each colour on thoroughly See also: white paper, and beyond this in important work there should be a progressive colour
See also: pattern that will show how the work looked when two, three or more colours were on, for this may at the finish be invaluable to show where error has crept in, and is in any event an immense aid to the machine minder
.
In regard to paper, a description made of rag or rag and See also: esparto is most desirable for all work on grained stones, but for work in ink and consequently from polished stone a good coated paper with sufficient " size " in it is frequently desirable; this paper is generally called " chromo " paper
.
There is at the present time very little encouragement for the high class of chromo-lithography that was so much in evidence from 1855 to 1875, but there is little doubt that the work could be done equally well by the present-day craftsmen if the demand revived
.
Belonging to the period mentioned, distinguished examples of chromo-lithography are " Blue See also: Lights," after See also: Turner, by Carrick; " See also: Spanish Peasants " and the Lumley portrait of See also: Shakespeare, by Risdon; " See also: Queen See also: Victoria receiving the See also: Guards," by W
.
Bunney, after John See also: Gilbert; and the series of chromos after John
See also: Leech, produced under the general direction of Vincent Brooks
.
A small proportion only of the Arundel Society's prints were executed in England, but many reproductions of water-colours after Birket See also: Foster, See also: Richardson, Wainwright and others were executed by Samuel Hodson, See also: James Lewis and others
.
Perhaps the most consistently good work of
See also: modern times has been the reproduction of Pellegrini's and See also: Leslie See also: Ward's drawings for Vanity Fair, which from 1870 to 1906 were with very few exceptions executed by the firm of Vincent Brooks, Day & Son
.
Transfers.—A very large proportion of work is got on to the stone by transfer, and there is no more important part of the business perhaps at the present time
.
When there is so much original lithography (lone on grained paper by artists of eminence, the transferring of grained paper drawings is the most important . The stone most desirable for this purpose will be neither a grey nor a See also: light yellow, but one that stands See also: mid-way between the two; it should be very carefully polished so as to be quite free from scratches, and brought to See also: blood-heat by being gradually heated in an iron cupboardprepared with the necessary apparatus
.
The methods that some-times prevail of pouring boiling water over the stone, See also: heating with the flame of an ordinary plumber's lamp, or even heating the surface in front of a fire, are ineffective substitutes, for the surface may thus become unduly hot and spread the work, and there is no increased tendency for the chalk to enter into the stone and thus give the work a long life
.
If there are no colours or registration troubles to be considered, it is well to place the transfer in a damping book till the composition adheres firmly to the finger, before placing it on the stone; it should then be pulled through twice, after which it should be damped on the back and pulled through several times; after this has again been well damped the paper will be found to peel easily off the stone, leaving the work and nearly all the composition attached; the latter should then be very gently washed away
.
In cases where the work for some reason must not stretch, such as the hills on a map, it will be necessary to keep the transfer dry and put it on a wet stone, but a piece of the margin of the paper should be tested to see that it is of a class that will adhere to the stone the first time it is pulled through
.
Unless the adhesion is very See also: complete it may not be safe to pull it through more than once
.
For a small number of copies a very moderate " etch " is desirable, but for a long run, where the See also: object is to secure a good edition rather than a few good proofs, the Eberle system may be adopted
.
This method consists in protecting the work with finely powdered resin and then applying the flame of an ordinary plumber's lamp; this will melt the protecting medium round the See also: base of each grain of work and allow of a very vigorous " etch " being applied
.
As before stated it is not unusual to secure 2000 to 3000 good copies in the machine after this treatment; but the rollers, the ink and the superintendence must be of the best
.
When the artist who is not a professed lithographer desires to make tints to his work, a reversed offset on grained paper should be made for each colour; this is done by pulling an impression in the usual way on a hard piece of paper, and while it is yet wet this should be faced with a piece of grained paper and pulled through again, when the grained paper will be found to have received the greater portion of the ink; this should be immediately dusted with offset powder of a red shade to prevent the grease passing into the paper, and the drawing of the tints should then be proceeded with in the usual way
.
Another method of transfer work is to pull impressions from copper or steel plates in transfer ink; it is in such way that simple etchings like those of See also: Cruikshank, Phiz and others are produced, and nearly all commercial work such as maps, See also: bill heads, &c., are prepared in the same manner
.
Beyond this, much work is done in lithographic ink on what is called writing transfer paper, such as circulars, See also: law writing for abstracts, specifications and plans
.
Machinery.—The chief items are the hand presses and the machines, whether flat See also: bed or rotary, the principal places of manufacture being See also: Leeds, See also: Otley and See also: Edinburgh
.
Stimulated by American competition, the standard of excellence in the United Kingdom has been very considerably raised of late years
.
The rotary machines have only been possible since the more frequent use of aluminium and zinc, but these materials are more suitable to receive transfer than for the general use of an office, the chief reason being that corrections on stone are more easily accomplished and more lasting when done
.
Preliminary work is therefore frequently done on the stone and transferred to plates for the machine
.
The question is very frequently asked as to how the necessary registration of the colours is secured; it may be stated for the benefit of the See also: amateur that in hand printing this is generally done by pricking with a pair of needles through printed marks present on each stone ; but in the machine this has been done in different ways, although in quite early days " pointing " or " needling " was done even on the machine
.
On modern machines this registration depends on the accurate cutting of the edge of the paper, of which at least one corner must be an absolute right angle
.
The paper is then laid on a sloping See also: board in such a way that the longest of the two true edges gravitates into the gripper of the machine, the stops of which move slightly forward as the gripper closes; simultaneously what is called the " side See also: lay " moves forward automatically to a given extent, and in this way at the critical moment the sheet is always in the same position in regard to the stone, which has already been firmly secured in the bed of the machine
.
Quite recently a new method has come into use that is probably
destined to be a great aid to the craft in its competition with other
methods
.
This is known as offset printing; it is more a matter of
evolution than invention, and proceeds from the method adopted in
tin-plate decoration so much used for box-making and lasting forms
of advertisement
.
It consists in bringing a sheet of See also: rubber into
contact with the charged stone and then setting-off the impression
so obtained upon card, paper, pegamoid, cloth or other material,
the See also: elasticity of the rubber making it possible to print upon rough
surfaces that have been previously unsuited to lithographic printing
.
Both flat bed and rotary machines are available for this system, the
latter being restricted to zinc or aluminium plates, but giving a high
speed, while the former can use both stones and See also: metal plates and may
be more effective for the highest grade of colour work; by both
classes of machines the finest engraved note headings can be printed
on rough paper, and colour work that has for so long been confined
16
to coated or burnished papers will be available on surfaces such as the artists themselves use
.
The following See also: treatises may be referred to with advantage by those in See also: search of more detailed information: A Complete Course of Lithography, by Alois Senefelder (R
.
Ackermann, See also: London, 1819); The Grammar of Lithography, by W
.
D
.
See also: Richmond (13th edition, E
.
See also: Menken, London); Handbook of Lithography, by David See also: Cumming (London, A
.
& C
.
Black)
.
The first of these will only be found in See also: libraries of importance; the others are present-day text-books
.
(F
.
V
.
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