Online Encyclopedia
Search over 40,000 articles from the original, classic Encyclopedia Britannica, 11th Edition.
PRINTING (from Lat. imprimere, O. Fr....
Online EncyclopediaEncyclopedia Home :: PRE-PYR
del.icio.us it!
|
See also:PRINTING (from See also:Lat. imprimere, O. Fr. empreindre)
, the See also:art or practice of transferring by pressure, letters, characters or designs upon See also:paper or other impressible surfaces, usually by means of See also:ink or oily pigment
.
As thus defined, it includes three entirely different processes: copperplate See also:printing, lithographic or chemical See also: It is not clear how the first printers struck off their copies, but without doubt See also:Gutenberg did use at an See also:early See also:period in his career a See also:mechanical press of some See also:kind, which was constructed of wood . In fact he could not have produced his famous See also:forty-two line See also:Bible without such aid . The earliest picture of a press shows roughly the construction to have been that of an upright See also:frame, the See also:power exerted wooden by a movable handle, placed in a See also:screw which was See also:Hand- tightened up to secure the requisite impression, and presses. was loosened again after the impression was obtained . The type pages were placed on a flat See also:bed of solid wood or stone, and it was quite a labour to run this bed into its proper position under the See also:hanging but fixed See also:horizontal See also:plane, called the platen, which gave the necessary impress when screwed down by the aid of the movable See also:bar . This labour had to be repeated in See also:order to See also:release the printed See also:sheet and before another copy could be struck off . This same press, with a few modifications, was apparently still in See also:general use till the early See also:part of the 17th century, when Willem Janszon Blaeu (1571–1638) of See also:Amsterdam, who was appointed See also:map maker to the Dutch See also:Republic in 1633, made some substantial improvements in it . Our first authority on printing, See also:Joseph See also:Moxon, in his Mechanick Exercises, as Applied to the Art of Printing (vol. i., 1683), says, " There are two sorts of presses in use, viz. the old See also:fashion and the new fashion," and he gives See also:credit to Blaeu for the invention of the new and decidedly improved press (fig . 1) . Blaeu's improvement consisted of putting the spindle of the screw through a square See also:block which was guided in the wooden frame, and from this block the platen was suspended by wires or cords . This block gave a more rigid platen, and at the same See also:time ensured a more equal See also:motion to the screw when actuated by the bar-handle . He also invented a See also:device which allowed the bed on which the type pages were placed to run in and out more readily, thus reducing the See also:great labour involved in that part of the work of the older See also:form of press, and he also used a new kind of See also:iron See also:lever or handle to turn the screw which applied the necessary pressure . The value of these various improvements, which were in details rather than in principles, was speedily recognized, and the press was introduced into See also:England and became known as the " new fashion." From this it will be observed that in a general way there had only been two kinds of wooden presses in use for a period of no less than three See also:hundred and fifty years, and when the work of some of the early printers is studied, it is marvellous how often See also:good results were obtained from such crude appliances .
The iron press (fig
.
2) invented by See also:
There was also another lever to the arbor head in addition to that of the spindle head; and lastly, the screw itself was so enlarged that it greatly increased the power
.
The platen was screwed on to the under surface of the spindle; the table or bed had slides underneath which moved in, and not on, ribs as in the older form of press, and was run in and out by means of strips of webbing fastened to each end and passed See also:round a See also:drum or See also:wheel
.
As the platen was very heavy the operator was assisted in raising it from the type-forme by a See also:balance See also:weight suspended upon a hooked lever at the back of the press
.
This somewhat counterbalanced the weight of the platen, raised it after the impression had been taken, and brought the bar-handle back again to its See also:original position, ready for another pull
.
The Stanhope press, which is still in use, was soon followed by other hand-presses made of iron, with varying changes of details
.
The most successful of these were the See also:Albion and Columbian presses, the former of See also:English manufacture, and the latter invented (1816) by an See also:American, See also:George Clymer (1754–1834), of See also:Philadelphia
.
The Albion press (fig
.
3), which was designed by See also:Richard Whittaker See also:Cope, was afterwards much improved upon by See also: On the return of the bar the platen is raised by a See also:spiral See also:spring, placed in a box and fixed at the head of the press . The larger sizes of these presses usually See also:print a sheet of See also:double See also:crown, measuring 30X20 in . Although the Columbian is not so much in demand as the Albion, it is still employed for heavy hand-work because of its greater stability and power . This power is acquired by a very massive lever, moving on a See also:pivot See also:bolt in the top of the near side of the staple, and passing across the press to the further side of the frame, at which end the power is applied through the coupling-bar by a bar-handle working from the near side . The platen is attached to the centre of the lever by a square bar of iron, and its vertical descent is assured by two projecting guides, one from each cheek; it is then raised from the type-forme, and the iron bar carried back by two levers—the one attached to and above the head and weighted with the See also:eagle; the other behind the press, attached to the See also:arm to which the coupling-bar is fixed, and which also has a weight at the end . The great power of this press adapts it to the working of large and solid formes in printing, but it is somewhat slower in See also:action than the Albion press, which is both lighter in construction and quicker in working . The See also:average output of the modern hand-press, when all is made ready for running, is about two hundred and fifty impressions per See also:hour . This number, it should be said, is the product of two men who work together as " partners." One inks the type-forme and keeps a See also:sharp look-out for any inequality of inking, and See also:sees generally that the work is being turned out in a workmanlike manner . The other See also:lays on the sheet to certain marks, runs the See also:carriage in under the platen, and pulls the bar-handle across to give the necessary impression . He then runs back the carriage and takes out the printed sheet, which he replaces by another sheet, and repeats the different operations for the next impression . During the See also:interval between taking off the printed sheet and laying on the next one his partner inksthe type surface with a See also:roller which carries just sufficient ink properly distributed to preserve uniformity of " See also:colour." Having dealt with hand-presses, we must now go back to the end of the 18th century, when the first experiments were made to devise some mechanical means of producing larger printed sheets, and at a quicker See also:rate . In England the broad distinction between " presses " and " See also:machines " is generally considered to See also:rest in the fact that the former are worked by hand, and the latter by See also:steam, See also:gas or See also:electricity; and the men who work by these two methods are called respectively " pressmen " and " See also:machine minders " or " machine managers." But in See also:America the terms " presses " and " pressmen " are universally applied to machines and the men who operate them . For the purposes of this article presses and machines are used as synonymous terms . Various schemes had been propounded with a view of increasing the output of the hand-press, and in 1790 William See also:Nicholson (1753–1815) evolved his ideas on the The First subject, which were suggestions rather than definite See also:cylinder inventions . Nicholson was not a printer, but, as he Machine. was an author and editor, it is presumed that he had some knowledge of printing . His proposals were to print from type placed either on a flat bed or a cylinder, and the impression was to be given by another cylinder covered with some suitable material, the paper being fed in between the type and the impression cylinder, and the ink applied by rollers covered with See also:cloth or See also:leather, or both . While Nicholson's schemes did not bear any See also:practical result they certainly helped others later on . His See also:suggestion to print from type made wedge-shaped (that is, smaller at the See also:foot and wider at the top) to allow of its being so fixed on a cylinder that it would radiate from the centre and thus See also:present an even printing surface, was adopted later by Applegath and others, and really was the first conception of printing on the rotary principle which has now been brought to such perfection . It was left to See also:Friedrich See also:Konig (1774–1833), a See also:German, to produce the first really practical printing machine . His invention was to print type placed on a flat bed, the impression being given by a large cylinder, under which the type passed, but his inking appliances were not satisfactory . He induced the proprietor of The Times (See also:London) to take two of these machines, and in 1814 that newspaper was printed with steam power at the rate of 1 roo impressions per hour, a great advance on the number produced up to that time . Both Nicholson's and Konig's machines printed only one side at a time—the second or backing printing being a See also:separate and distinct operation—but they really embodied the general principles on which all other machines have been constructed or modelled . It will be understood that Nicholson's theories were to print both from the flat and from type arranged in circular or cylinder form . These two principles are defined as reciprocating, for the flat bed which travels backwards and forwards; and rotary, for that which continuously revolves or rotates . See also:Kong's invention was a reciprocating one . Two other classes of presses of somewhat different design were largely in operation in the middle of the 19th century—the " double platen," which still printed only one side at each impression from each end, and the " perfecting machine," which was made with two large cylinders and printed from two type-formes placed on separate beds . Although the latter machine turned out sheets printed on both sides before it delivered them (hence its name), the second impression was still a distinct operation . The double platen press was somewhat Double analogous to the hand-press, both the type beds Platen and impressions being flat . A machine of this kind, Machine. if it printed a sheet of double demy, which See also:measures 35 X 221 in., was about 13 ft. in length, and the platen itself, of very massive construction, was placed in the centre . This platen had a perpendicular motion, being guided in grooves and worked by a connecting See also:rod fixed to a cross See also:beam and See also:crank, which acquired its motion from the main See also:shaft . There were two type beds and two inking tables, which travelled backwards and forwards, and one platen only, situated in the middle of the machine, which in turn gave the needful impression as the type-formes passed underneath . The sheets were laid or fed to certain marks between the frisket and tympan, and when these were closed together the carriage was propelled under the platen and the impression was given to that portion of the machine, while at the other end another sheet was being fed in ready to receive its impression in due course . It was once thought that the finest work could not be produced by a cylinder impressing a surface in the progress of its reciprocating motion, but that it was likely to give a slurred or blurred impression . This is why machines of flat construction were so See also:long employed for the best class of work . But cylinder presses are now made so truly turned, and geared to such nicety, that this See also:idea no longer prevails . The cylinder press is able to produce generally quite as good work as the double platen, its See also:speed is much greater, and it requires a smaller amount of power to drive it . The perfecting machine has had a great See also:vogue, and has been much improved from time to time, especially in America, Perfecting though the two-revolution machine in See also:recent years machine. superseded it, whether temporarily or not being still uncertain . We shall See also:deal with it more fully below in relation to the modern and more complicated class of machinery; and this also applies to the See also:ordinary stop or single cylinder, and small platen machines, both of which have been in use many years, and are still in demand . Before the general introduction of rotary machines which print from curved stereotype plates from an endless See also:web or See also:reel Type of paper (see below), several other presses of a revol-Revolving ving See also:character were made, to some extent based on Machines . Nicholson's ideas . The first printing surface used was ordinary type, because the difficulty of curving the stereo-type plates had not been surmounted . This type was fixed, both in vertical and in perpendicular positions, upon a cylinder, round which rotated other cylinders, which held and compressed the sheets against the larger one, which also revolved and carried the printing surface . These machines were made to print several sheets at a time, and were called four-, six-, eight- or ten-feeders, according to the number of sheets fed in and printed . They necessitated a great deal of labour, because each feed required a separate layer-on and taker-off besides the superintending printer, and other hands to carry away the sheets as fast as they accumulated at the different taking-off boards . Besides, these sheets all had to be folded by hand . In this class of machine various improvements were made from time to time by different manufacturers, each profiting by the experiences of the others, and two kinds of such revolving presses may now be given as examples . After many experiments See also:Augustus Applegath (1789–1871) in 1848 constructed for The Times (London), a machine which was an eight-feeder, built entirely on the cylindrical principle, the cylinders placed not in a horizontal but in a vertical position . The type was fixed on a large cylinder, and instead of the printing surface presenting a complete circle, the different columns were each arranged so as to form a See also:polygon .
Around this large type cylinder were eight smaller ones, all upright, for taking the impression for each of the eight sheets fed in separately, and rollers were so arranged as to apply the ink to the type as it passed alternately from one impression cylinder to the other
.
The sheets were laid in from eight different feed-boards, placed horizontally, and they passed through tapes, when they were seized by another See also:series of tapes and then turned sideways between their corresponding impression and type cylinder, thus obtaining sheets printed on one side only
.
The impression cylinder then delivered the sheets separately (still in a vertical position) into the hands of the boys employed as takers-off
.
The results from this press were, at the time, considered fairly satisfactory, the number of copies (about 8000) printed per hour from one type-forme having been materially increased by the employing of the eight different stations to feed the sheets in, all of which in turn were printed from the same single type surface
.
About 1845 See also:Robert See also:Hoe & Co. of New See also:York, and subsequently of London, had constructed, to meet the increased demands of See also:newspapers, the " Hoe Type Revolving Machine," one good point of which was an apparatus for securely fastening in the type on a large central cylinder fixed horizontally
.
This was accomplished by the construction of See also:cast-iron beds, one for each separate See also:page (not See also:column, as in Applegath's machine)
.
The column rules were made tapering towards the feet of the type, and the type was securely locked in on these beds so that it could be held firmly in the required position to form a complete circle, thus allowing the cylinder to revolve at a greater speed than Applegath's, which was polygonal
.
Around the large type cylinders were placed the smaller impression cylinders, the number of these being governed by the output required
.
Hoe's first presses were four-feeders, but as many as ten feeds were supplied, as in the See also:case of the two presses built to replace the Applegath machine for The Times, each of which produced about 2000 impressions from each feed, making a See also:total of 2o,000 per hour, printed on one side, or from two machines 20,000 sheets printed on both sides
.
As will be observed, the only See also:differences in principle between these two type revolving machines were in the positions of the respective cylinders, and the fixing of the type to form a printing surface
.
It was Sir See also:Rowland See also: See also:Bullock (1813–1867) of Philadelphia who in 1865 invented the first machine to print from a continuous web of paper . This machine had two pairs of cylinders, that is, two type or stereotype cylinders, and two others which gave the impression as the web passed between . The second impression cylinder was made somewhat larger so as to give a greater tympan surface, to lessen the off-set from the side first printed . In his machine the stereo-type plates were not made to fill the whole periphery of the forme cylinders so as to allow of the sheets being cut before printing, a difficulty which the first machines did not satisfactorily over-come . The sheets were severed by knives placed on the cylinders, and when cut were carried by grippers and tapes; and delivery was made by means of automatic See also:metal fingers fixed upon endless belts at such distances apart as to seize each sheet in See also:succession as it left the last printing cylinder . These presses were not at first reliable in working, especially in the cutting and delivery of the sheets after printing, but were finally so far improved that the Bullock press came into quite general use . The inventor was killed by being caught in the See also:driving See also:belt of one of his own presses . Modern Presses . The machines invented during the second half of the 19th century and still in general use, are best classified as follows: 1 . The iron hand-press, such as the Albion or the Columbian, used for the pulling of proofs, or for the printing of limited See also:editions de luxe . Classifica- 2 . Small platen machines (worked by foot or tion of power) used for the printing of See also:cards, circulars and modern small jobbing or commercial work . Presses and 3 . Single cylinder machines (in England generally Machines. called " Wharfedales "), usually built on the " stop " cylinder principle, and printing one side of the sheet only . 4 . Perfecting machines, usually with two cylinders, and printing or " perfecting " both sides of a sheet before it leaves the machine, but with two distinct operations . 5 . Two-revolution machines, which, although with but one cylinder, have largely superseded perfecting machines, as their output has been increased and the quality of their work compares favourably with that of the average two-cylinder . 6 . Two-colour machines, usually made with one feed, that is, with only one cylinder, but with two printing surfaces, and two sets of inking apparatus one at each end of the machine . Occasionally these machines are made with two cylinders . 7 . Rotary machines, printing from an endless web of paper from curved stereotype or electrotype plates, principally used II for newspaper or periodical work . They are made to print upon a single reel, or upon two, four, six or even eight reels, in both single or double widths, i.e. two or four pages wide . The hand-press has already been sufficiently described, and we may proceed to deal with the other classes . The small but useful platen machine (fig . 4) is very largely employed in those printing-houses that make commercial work Platen a speciality . The smaller machines can be worked Jobbing with the foot, but if the See also:establishment is equipped with Machines. power it is customary to See also:gear them for driving . The larger machines require power . As its name implies, the type bed and impression platen are both flat surfaces as in the hand-press, but as they are self-inking and are easily driven, the average output is about See also:i000 copies per hour, and but one operator is required, whereas two men at a hand-press can produce only 250 copies in the same time . In design these platen presses usually consist of a square frame with a driving shaft fixed horizontally across the centre of it . This shaft is attached to a large See also:fly-wheel which gives impetus to the press when started and assists in carrying over the impression when the platen is in contact with the printing surface . The type-forme is usually fixed in an almost vertical and stationary position, and it is the platen on which the sheet is laid which rises from the horizontal position to the vertical in order to give the necessary impact to produce a printed impression from the type-forme . Practically this platen is, as it were, hinged at the off side, nearest the type bed, and its rise and fall is effected by the use of two arms, one on each side of the platen, which derive an See also:eccentric motion from cams geared in connexion with the shaft . When the sheet is printed and the platen falls back to the horizontal the operator removes it with one hand and with the other lays on a fresh sheet . Generally the larger of these machines will print a sheet up to 21 X 16 in . The modern single or " stop " cylinder, quite different in construc-"Wharfe- tion from the old single cylinder machines, largely See also:sue-See also:dale " ceeded the double platen machine . The principle of the Machines. stop cylinder was really a See also:French invention, but it has been more commonly adopted in Great See also:Britain, where the machines are known as " Wharfedales " (fig . 5) . They are muchused for the printing of books and commercial work . The average production is about i000 copies per hour . The type bed travels with a reciprocating motion upon rollers or runners made of steel, the bed being driven by a simple crank motion, starting and stopping without much See also:noise or vibration . All the running parts are made of hard steel . The cylinder is " stopped " by a See also:cam motion while the bed is travelling backward, and during this interval the sheet to be printed is laid against the " marks," and the gripper closes on it before the cylinder is released, thus ensuring great accuracy of See also:lay, and consequent good See also:register . After the impression is made the sheet is seized by another set of fingers and is transferred to a second and smaller cylinder over the larger one, and this smaller cylinder or drum delivers the sheet to the " flyer," or delivery apparatus, which in turn deposits it upon the table . The inking arrangements are usually very good, for, by a See also:system of racks and cogs which may be regulated to a nicety, the necessary See also:distribution of ink and See also:rolling of the printing surface runs in gear with the travelling type bed or See also:coffin . All the accessories for inking are placed at the end of the machine, the ink itself being supplied from a ductor, which can be so regulated by the keys attached to it as to let out the precise amount of pigment required . The ink passes to a small solid metal roller, and is then conveyed by a vibrating roller made of See also:composition to a larger and hollow metal cylinder or drum which distributes the ink for the first time . This revolves with the run of the machine and at the same time has a slight reciprocating action which See also:helps the distribution . A second vibrating composition roller conveys the ink from this drum to the distributing table or ink slab, on which other rollers, called distributors, still further thin out the ink . As the type bed travels, larger composition rollers, called inkers, placed near the cylinder, adjusted to the requisite pressure on the type, pick up the necessary amount of ink for each impression and convey it to the type as it passes under them . Usually three or four such rollers are required to ink the forme . The perfecting machine is so named because it produces sheets printed on both sides or, in technical See also:language, " perfected." This operation is performed by two distinct printings . This perfecting class of machine has been in use a great many years, Machines. although both the stop-cylinder and the two-revolution press have to some extent superseded it . It is perhaps best adapted for the printing of newspapers or magazines having circulations that do not require rotary machines intended for long runs . Although some perfecting machines have been made with one cylinder only, which reverses itself on the old " See also:tumbler " principle, they now are made with two cylinders, and it is with this class that we are particularly concerned . There are various makes of perfecting machines of which the See also:Dryden & Foord is shown in fig . 6; among the best recent typed is the See also:Huber Perfecter . Although the two-type beds have a reciprocating motion, as in the ordinary one-sided press, the two cylinders rotate towards each other . The frame of the machine, owing to the fact that it contains two carriages and a double inking apparatus, is long, the exact See also:size depending on the size of the sheet to be printed . 
See also:Close to the large cylinders are the inking rollers, which take the necessary amount of ink, each set from its own slab as it passes under, and these rollers convey the requisite ink to the printing surface as the forme-carriage runs under its own cylinder . The distinctive feature is the ingenious manner in which the sheets are printed first on one side, and then on the other . This is performed by carrying them over a series of smaller cylinders or drumskby means of tapes . The See also:pile of sheets Machine . to be fed in stands on a high See also:board at one end . The sheet is laid to its See also:mark and is conveyed round an entry drum; thence it is carried round the first impression cylinder, and under this, moving at the same speed as the cylinder, is the type bed containing the inner of broad tapes which See also:lie on the laying-on board and are fastened to a small drum underneath it . This drum has a series of small cogs which move the web or tapes in the same direction . The sheet is laid to a back mark on the tapes, and is propelled between two rollers forme already inked . The paper then receives its impression on the first side . In the older type of machine it is next led up to the right-hand one of the two See also:reversing drums, which are placed above the large printing cylinders, and over which it passes with the printed side downwards . It is then brought under the second or left-hand drum, and so on to the other large impression cylinder, with the See also:blank side of the sheet exposed to the type of the See also:outer forme on the table underneath . Thus it will be seen that the sheet is reversed in its travel between the first and second large cylinders which give the impression . The sheet is then finally run out and delivered in the space between the two large cylinders, and laid on the delivery board—usually with the aid of flyers . In the more recent type of See also:direct into the machine . Another variety employs grippers some-what after the manner of the ordinary single cylinder . The Anglo-French perfecting machine is one of that class . As a See also:rule most double-cylinder presses produce on an average about i000 copies per hour, printed both sides . The two-revolution machine is another one-cylinder machine built on the reciprocating principle . Its speed is greater than the stop cylinder (it may be geared to produce from 1500 to Two . 2000 copies per hour, printed one side only) . The Revolution Miehle (fig . 7), which is of American design but now made Machines also in Great Britain, is a good example of this kind of Mac6ie. machine and is much used, especially for illustrated work . It has perfecting machines the sheet is fed directly into grippers, See also:change taking place when grippers on each cylinder meet, the outer forme grippers taking the sheet from the inner forme grippers . This is a general description of the principles on which these machines are built, but, as in other classes, there are many See also:variations in details . For example, there are the drop-bar, the web and the gripper methods of feeding these presses . In the first case a bar descends upon the paper after it is laid to point marks, and this bar, having a rotary motion, runs the sheet between a roller and a small drum into the machine . The web arrangement consists of a seriesthe high over-feedboard, and the taking-off apparatus is automatic but on a different See also:plan from that of the ordinary Wharfedale, the sheets being carried over tapes with the freshly-printed side upper-most, thus preventing smearing; they are then carried on to the heap or pile by the frame or long arms placed at the end of the machine . A recent feature of this machine is the tandem equipment, whereby two, three or even four machines may be coupled together for colour work . Only one layer-on is required and register is obtained automatically throughout . The principle of the two-revolution press is that the cylinder always rotates in the same direction, and twice for each copy given, once for the actual impression, and again to allow of the return of the forme-carriage in its reciprocating action . This also allows time for the feeding in of the next sheet to be printed . Among other advantages claimed for this press one is that the See also:movement which governs the action of the type bed in reversing is so arranged that the See also:strain which sometimes occµrs in other reciprocating machines is considerably reduced; another is that the registering or correct backing of the pages on the second side in printing is uncommonly good; but this depends much upon the layer-on . In many of the old kinds of two-revolution machines, owing to the cylinder being geared separately from the type bed, it was See also:apt to be occasionally thrown out, but in the Miehle, for instance, it is only out of gear in reversing, and in gear while printing . Great strength is imparted to the frame, and the type bed is particularly rigid . These points, together with a truly turned and polished cylinder, with carefully planned means of See also:adjustment, much simplify the preparation of making-ready of any kind of type-forme or blocks for printing, which is carried out much in the same way as on the ordinary single cylinder, but in a more convenient manner . Many of these machines are made to print four double crowns, 6o X 40 in., or even larger . continuously rotate, the web of paper travelling in and out, in a See also:serpentine manner, between various cylinders of two characters—one (the type cylinders) carrying the surface to be impressed, usually curved stereotype plates, and the other (the impression cylinders) giving the desired impression . Such a press, if driven by electric power, is set in motion by merely pushing a See also:button or small switch, a See also:bell first giving warning of the press being about to move . The number of duplicate sets of stereotype plates to be worked from by these presses is determined by the size and number of the pages to be printed, and this in turn is regulated by the capacity of the machine . As already explained, the forerunners of the rotary presses of the present See also:day were the type-revolving printing-machines, and, whilst they were still being used, experiments were being made to cast curved stereotype plates which would facilitate and simplify the work of producing newspapers . This was successfully accomplished by the use of flexible paper matrices, from which metal plates could be cast in shaped moulds to any desired See also:curve . These plates were then fixed on the beds of the Hoe type revolving machine, which were adapted to receive them instead of the movable type-formes previously used . This new method enabled the printers The two-colour machine is generally a single cylinder (fig . 8) with one feed only, and the bed motion reciprocating . The two Two-Colour See also:colours are printed each at one revolution from the two Machines. type-formes as they pass under the cylinder, which rotates twice in its travel . A double inking apparatus is of course necessary, and the inking arrangements are placed at the two extreme ends of the machine . In comparison with the ordinary single cylinder the two-colour machine is built with a longer frame, as is necessary to allow the two type-formes to pass under the cylinder, both in its travel forward and on its return . This cylinder on its return is stationary, in fact it might be called a double or rather an alternative stop-cylinder machine, with the inking facilities arranged somewhat on the same plan as on either a two-feeder or a perfecting machine . These two-colour presses are intended only for long runs, short runs may be worked to See also:advantage separately on the ordinary single-colour machine . Generally, with the exception just mentioned, the machine is much the same as the ordinary stop or Wharfedale . Before leaving the subject of printing with the reciprocating bed- motion, it may be mentioned that although in all modern ma |