An exact description of all presses used hitherto for lithography would demand a book that would nearly equal the present one in magnitude. Many drawings would be necessary, which would increase the cost of this text-book without adequate benefit, as I have learned that one rarely can find a mechanician skillful enough to make a machine even when he has the very best description and a perfect illustration before him. I advise all who intend to enter lithography to send for a model to Munich or some other place where the art is being practiced with success. I myself am willing to furnish exact models for the price of one louis d'or, which must be remitted with the order.
There is no press as yet that is so perfect for lithography that it leaves nothing to be desired. The press whose plan I laid before the Royal Academy of Sciences in Bavaria, which does its own inking-in and which can be worked by water-power, has not yet been built on a large scale, so that its value cannot be stated exactly.
I am only too well aware, however, of a grave defect in lithography, which is that the beauty and even the number of impressions depend mainly on the skill and the industry of the printers. A good press is necessary, to be sure; but even with the best a poor workman will produce nothing but trash, because in this respect lithography is far more difficult than any other printing-process. I shall not admit that lithography has made a great step toward the utmost perfection until the erring work of the human hand has been dispensed with as much as possible and the printing is done almost entirely by machinery. Therefore I am determined to realize the ideas I have in this direction and I shall inform the friends of the art of my success at once.
I
PROPERTIES OF A GOOD PRESS
It has been observed that inscriptions, and particularly drawings, look better on the stone than on the impression afterward made from the stone. Partly this may be due to the color of the stone which softens the picture, because an impression made on yellow paper resembling the stone color looks very much like the drawing on the stone. But the great cause of the difference is that the color does not transfer itself to the paper with the degree of strength and clearness that it possesses on the stone. That this perfect degree can be attained, none the less, there are many successful impressions to prove.
If the plate is well designed and well prepared, it will take the color well and clearly, but the printer may apply too much or too little, the color may be too hard or too soft, or, even if the stone is properly inked, the paper may accept color poorly or be too damp or dry. Chiefly, however, it is the press, according to my experience, that most affects the quality of an impression.
In most lithographic presses the printing is done by the so-called scraper. This is a thin slat of hard wood, mostly maple, pear, or boxwood. It is one line thick on the side intended to do the printing, and the mechanism of the press forces it on the paper, which is on the stone and covered with an overlay of waste paper and tensely stretched leather. This pressure forces the color against the paper along the whole length of the slat, and only one line broad. The scraper is forced bit by bit over the entire plate, or it remains motionless and the plate is drawn underneath it. It will be observed that this kind of press does not produce the entire impression vertically and at once as in book-printing, but that it is successive, as in copper-plate printing, with the difference that the copper-plate press uses a roller instead of a scraper.
As the scraper must be pressed down with great force (often as much as sixty and more hundredweight) and must pass over the leather with this immense pressure, there is a tremendous friction, and despite the fact that the leather is tensely stretched and lubricated with fat, it is considerably pulled and strained by the scraper. This pulling and straining communicates itself to the paper under the leather. Thus all the lines of the design become a little bit squashed in the direction described by the scraper. If, however, the leather is very good and very tensely stretched in the frame, if it is well lubricated, and if the printing-paper with its underlay is not too wet, the pulling is inconsiderable so that scripts and drawings in broad effects are not affected noticeably. Drawings in detail, however, and crayon work wherein there is hardly a perceptible space between the dots, are so affected by the slightest displacement that they produce a smeared, sooty impression.
The scraper has a second fault. If the paper has impurities, it injures the scraper readily. A groove scratched into the scraper will prevent any further good impression if the injury is considerable, because it will leave a streak. The only remedy is to take the scraper off and plane it, fashioning it accurately to the surface of the stone. I have tried to remedy this by making a scraper of metal. As this causes even more friction than wood, I laid a strip of strong paper over the scraper, which generally was good for three hundred impressions before it was worn out. Then I merely needed to move it forward a bit; so that a strip of paper as long as the scraper and six inches wide was available for some thousands of impressions. The pressure attained with a metal scraper is greater than with wood; but it has the disadvantage that it is hard to print a stone whose surface is not absolutely level, whereas a wooden scraper can be planed to suit any irregularity in the stone.
The foregoing shows that a good lithographic press must have these two properties:— (1) It must not pull or shift the paper in the least.
(2) It must produce a uniform impression without weak spots or streaks.
The other properties it needs in common with other presses, such as:—
(3) It must be powerful enough to produce the necessary pressure.
(4) It must combine the greatest possible speed with this power.
(5) It must be easily operated, to save the workman.
All these qualities combined are not to be found in any press hitherto applied to lithography.
II
APPLICATION OF BOOK- AND COPPER-PLATE PRESSES TO LITHOGRAPHY
If we consider the peculiarities of book and copper print, we find a decided difference between them that affects printing importantly.
The letters of book-type are raised, the engraving in copper is depressed. It is evident that the former requires no such power for making impressions as the latter. Therefore the presses are so different that copper plates cannot be printed on a book-press and vice versa. Now, as the stone combines both the elevated and the depressed principles, the natural idea would be to combine the fundamental principles of both presses as nearly as possible for stone-printing. In book-print, only the types are exposed to the pressure, and in the average printed sheet these are only one fourth part of the entire surface. The remaining white space is not affected at all by the press. In the stone, however, the elevation of any part of a design is so slight that the entire surface is affected, and consequently a stone plate offers four times as much resistance. A book-press therefore would print a stone only if it were arranged for a pressure four times greater. Now, for a stone of the size of a letter-sheet the power required to print with one vertical pressure would be five or six hundred hundredweight, a pressure that could be supported only by a thick stone laid very exactly on a perfect foundation.
An ordinary copper-plate press increases the pulling of the paper so much in the case of a stone plate that the impression would be worthless. This pulling is not caused, as in the case of the scraper, during the impression itself, as already described, but it is caused before the impression through the endeavor of the cylinder to force the plate along under it. Once the stone is under the cylinder, the paper is not pulled noticeably, because the cylinder glides over the leather much more gently and with much less friction than the scraper.
This defect might be corrected:—
(a) By supporting the cylinder so that it would come down on the stone only at the point where the print is to begin. But as the stone must be drawn pretty well forward for convenience in inking, this would demand that the cylinder be revolved forward and backward again as far as is needed for the impression, which means a great demand on the strength of the printers, not to count the loss of time.
(b) A second way would be to plane off a piece two inches wide from the cylinder at the point where the impression is to begin. The stone could be forced under this space readily, and when the cylinder revolves, it presses forcibly at once without pulling the paper very much.
(c) The press might be fitted with iron wheels with cog teeth to engage similar cogs on the cylinder. This would prevent pulling, but the mechanical work would need to be very accurate.
(d) The best arrangement will be the following: Set the upper cylinder so high that the stone can be brought under it without touching. Then bring it down with a screw, or better still, with a lever that can be operated by the foot.
The first figure in the plate showing presses represents about how a copper-plate press is to be fitted for this work. On the whole, this is an ordinary copper-plate press, but the upper roller is set with its two axles or spindles in two iron levers, each of which is fastened to a piece of wood with iron screws one inch thick. Each of these pieces of wood is covered with strong sheet iron and can be adjusted higher or lower with two screws or with underlay of pasteboard. This is necessary that the press may be adjusted to varying pressures. The two other ends of the two levers, in which the cylinder sits, can be raised or lowered, so that the cylinder also can rise or sink. Now two springs or two weights are so adjusted that the cylinder with the levers always remains elevated. To force it down on the stone, an iron beam enters both sides of the press with two pegs so adjusted that when the beam is turned ninety degrees the levers are depressed at least two inches. As the cylinder is about in the middle of the two levers, it will thus be depressed one inch, which suffices to permit the stone to pass under it freely while it is elevated and gives the greatest pressure when it is depressed. However, the upper cylinder must not be one inch distant from the stone, but at the most only one fourth inch, for the remaining space of three fourths inch is required to provide margin for the elasticity of the various materials, and also to give margin for increased pressure whenever demanded.
On one end of the iron beam with the two pegs is an arm or lever which is joined to a thin stick with a treadle. This tread is so arranged that it remains elevated of itself. If the pressure is to reach sixty or more hundredweight, it must not be fastened directly to the treadle, but a second lever is required which is affixed to the side of the press.
Without going into tedious detail I cannot further describe this press. Mechanicians will understand me readily and perhaps be able to add many improvements. My belief is that a copper press so arranged would diminish all danger of squashing and pulling the impression, furnish powerful pressure, permit overlays of felt or fine cloth, and make possible considerable facility and celerity, which is a great advantage, because impressions always are better if too much time is not lost between inking and printing.
To safeguard the stone against cracking in such a press, the following points are to be noted:—
(1) The stone must be ground very true on the under side as well as the upper.
(2) Both cylinders must be perfectly true, and care is to be taken particularly that one cylinder is not thin toward the middle and the other thick, as this would easily crack the stone lengthwise. The board on which the stone rests must be equally true and uniformly thick. At the same time it must be very thin, only one half inch thick at most. It will get very heavily squeezed during the printing, and the more the impression approaches the centre, the more concave will it become. The parts farthest from the point of pressure then resist unduly if the board is thick, and thus become the chief cause of cracking the stone. If the rollers are very true and the stone is very uniform, it is almost impossible to crack it if it is passed between the two rollers without a board underneath. If the board is thin, it is as if it were not there.
I believe that competent mechanicians can improve the present presses greatly.
III
LITHOGRAPHIC PRESSES USED HITHERTO
Most owners of lithographic printeries have tried their hands at inventing presses, but in the end it has always been something based on the scraper or the cylinder principle. I myself have made more than twenty designs. Some were very useful and had advantages either in power or convenience, but generally were handicapped by some defect, so that I cannot even say with certainty which was the best of them all. So much depends on the mechanic's execution of one's plans, and a perfect design can be so spoiled by a workman that it is worthless.
I will, however, recount the best that has been done so far for lithography.
In Munich two kinds of stone presses are mostly used. They are:—
(1) The lever press, or, as the workmen generally call it because of its form, the Gallows Press.
(2) The Cylinder or so-called Star Press, the latter term being used because a star-shaped lever is commonly used instead of a crank to turn the rollers.
I have tried and found good the following:—
(3) A press with double levers.
(4) A gyrating or sliding press. I know also—
(5) The roller press used by Herr Andre.
(6) And the press of Herr Steiner in Vienna.
Herr MÜller in Karlsruhe and Herr Ackermann in London have a press with paper cylinders the construction of which is unknown to me.
IV
THE LEVER PRESS
This was the first press that I used with advantage, and it is used still in Munich in all important establishments for work that demands speed particularly. It would be an excellent printing-machine in all respects if it did not have the defect that its power cannot be increased much more than six hundredweight without forcing the workmen to undue exertions. Therefore it is no longer available for large plates or for works that require immense power. It is very good for pen designs not larger than a letter-sheet, and two workmen, one to ink-in and the other to print, can produce twelve hundred impressions in a day without hardship.
The pressure is produced by a lever six to twelve feet long, fastened to the scraper below and to a spring (an elastic board) above. It is connected with a tread, and when forced down, presses with the desired force on the scraper and so on the plate. The board holding the lever overhead must be partially movable like a spring because the lever describes a part of a circle on the plate below. Hence the pressure at the beginning and end of the impression is not so great as in the middle, and great care in choice of wood and manufacture is demanded to give the spring board the necessary elasticity and power combined. I have found a board of young dried pine the best, the dimensions being six feet long, eight inches wide, and two inches thick, provided that the fibres all ran lengthwise. It is not always possible to find a good board at once. Often I have found that the difference between two boards made a great difference in the effectiveness of two presses otherwise exactly the same.
The scraper arm consists of two parts, of which the shorter one, to which the scraper is fastened with a screw, is only one and one quarter feet long. The other part is as long as the height of the press permits. The higher a lever press is, the better is it, because then the circular motion described by the scraper wood approaches a straight line more and more, so that the press exercises a more uniform pressure during all stages of the impression and is easier to handle. The second illustration shows this kind of press in the moment when the impression has been finished, the printing-frame opened, and the scraper arm swung back again.
The printing-frame is much like a book-printing frame, and is furnished inside with a second small frame which holds the paper, being furnished with small springs or strings. When the frame has been turned over the stone, the paper must be at least half an inch from the stone to avoid smutting, which will occur if it touches. The paper must not touch the stone till pressure is applied, and then only on the spot pressed downward by the scraper.
As soon as both parts of the scraper arm are in a straight line, so that they form practically one piece, the scraper wood is pulled down and the printer draws it toward himself over the printing-frame and the stone plate. At this time the following is to be observed:—
(1) Both parts of the arm must be so fastened to each other that they may be bent like a knee, but once they are straight in line, they must stay in that position. It is well, therefore, so to adjust the parts that they will not be directly over each other, but rather exceed a straight line under pressure, and bend a little inward. The position of the scraper must be considered also. On the whole the following rule holds good: the point where both parts are united with a nail or a screw must not be in a perfectly straight line between the point where the scraper rests and the point where the arm is fastened above, but should be at least two and a half inches forward of that point. Otherwise the arm may spring outwards toward the workman and injure him severely. The third illustration shows the construction of the scraper arm and the scraper.
(2) The arm must be grasped as low as possible when being drawn toward one's self, in order to diminish the danger of springing outward. (3) The workman must press his body tightly to the table of the press to get proper leverage. Standing free, a man of moderate strength could not move the scraper at all when the pressure is on, but a man standing in correct position can do it without difficulty.
(4) Under very heavy pressure the inker-in, who stands on the other side of the press, can help by pushing.
The scraper is a piece of pear wood as long as the size of the plate demands. Its height is about four inches, its thickness one inch. The end that rests on the leather is trimmed down so that it has a thickness of only one line. This end must be especially true and planed to fit the stone, also neatly rounded off. It should be so fastened to the arm that it may be adjusted to the position of the stone. The stone does not always lie truly horizontal in the press, sometimes because it is not uniformly thick, sometimes because the underlay is not quite even, and sometimes because the press itself has been a little strained. If the scraper has been made properly, it will adjust itself to the stone, even if the scraper arm is not quite plumb on the stone, a condition that often occurs with small work, such as titles and other things that are at the end of a stone.
(5) For every press a number of scrapers of different dimensions must be in stock. Generally a lever press is so made that the printing-frame can be raised or lowered according to the thickness of the stone. Then the scraper must be changed accordingly.
(6) The connection of the upper board with the tread is made by a thin stick that is fastened to a lever below, by means of a small iron piece which contains several holes that serve to adjust the height of the tread according to need.
(7) The leather in the printing-frame is strong calfskin. It must be stretched very evenly and tensely and must be smeared from time to time very thoroughly with tallow.
(8) On the outer side of the frame there are four wooden strips that can be adjusted as desired. One serves to show the point where the impression is to begin. Another shows where it is to end. Both must be so strong that they can resist the scraper. The other two are adjusted at the sides and guide the scraper.
V
THE CYLINDER PRESSES
When Herr Professor Mitterer installed a lithographic institution for the Feyertags-Schule, the lever press appeared to him to demand too much labor, especially when powerful pressures were desired. He invented the so-called Cylinder or Star Press, which has its place in most establishments, especially those in other countries. It has had minor changes made in it by many persons, but on the whole, nobody has succeeded in improving it notably, except for a considerable improvement made by Herr Mitterer himself. My description will include this improvement.
The cylinder press might almost be called a reversed lever press. Herr Mitterer borrowed from it the idea of effecting the impression with a scraper, but he did not let it move over the plate, as in the lever press. He gave the scraper a fixed, immovable position while the stone was drawn through underneath, thus making his press resemble a copper-plate printing-press somewhat.
Illustration number 4 shows this machine in the moment when the impression has been made. In the middle of the machine is a cylinder ten to twelve inches thick and as long as the breadth of the press. It has strong iron spindles that revolve in well-lubricated brass bearings. Above the cylinder is a board on which is fastened the stone with the printing-frame. The scraper is on a strong lever that is held up by a counterpoise. When everything is ready for printing, the scraper is forced down. By means of a strong iron hook it engages the treadle and thus can be pulled down with the utmost tension. Then the cylinder is turned by means of two levers affixed to the crank, and this draws the stone and printing-frame through under the scraper. One workman alone can do this under ordinary pressure, but an appliance at the other end of the press enables a second workman to help.
VI
GYRATING SCRAPER AND DOUBLE LEVER PRESSES
I have already mentioned the gyrating scraper press. I have improved it considerably. It has the form of the ordinary lever press, but all the parts can be much lighter. For instance, the lever is only one and a half inches thick. The spring (the elastic board) is very elastic and need exert a pressure of only one hundred pounds. The little scraper is only an inch long and presses on the plate with a force of fifty pounds. The press is useful for very thin stones that might crack under greater pressure. The pressure, nevertheless, is great, because it is all exerted on such a small area. The press has two defects. It is easy to miss many parts of the design with the small scraper, and the paper is likely to stick to the leather, producing poor register. I have obviated these faults with the following invention: A large scraper is fastened to the lever to press on the plate with a force of one hundred pounds. A small one is fastened to this in such a manner that it can be moved to and fro easily. While one workman rubs to and fro with the small scraper, another draws the entire stone and printing-frame slowly along under the large one. If good underlays are used in addition, this process will produce beautiful work that cannot be produced so well with any other machine. However, a large field is left in this form for improvement.
The fact that the concentric motion produced by a single lever can be transformed into an almost straight motion by use of a second lever, led me to design a double lever press, which has turned out very successful, giving great force with speed. As its description would demand much space, and since on the whole it ranks equally with the improved cylinder press, I offer to send models to those who desire to have everything useful for the art.
VII
THE OTHER STONE PRINTING-PRESSES
The cylinder press of the Chemical Printery in Vienna would, without question, be of excellent service for the art if it were more powerful. Its construction is as follows: The stone is fastened to a table with the printing-frame which has fine felt instead of leather. To make the impression a brass cylinder eight inches thick is rolled over it. As this cylinder would not produce enough pressure from itself, despite its massive make, two iron beams are fastened to the axles. They pass through the table and are fastened to a box that contains iron or leaden weights. Unfortunately the space prevents the use of more than five or six hundredweights, and this is too little for the large surface of the cylinder, thus forbidding any sharp, clear impressions.
This kind of press could be greatly improved if it were built higher to give more room below for weights, or the beams could be lengthened and passed through the floor into a lower room, thus giving space enough to add weights up to fifty and more hundredweight.
The press of Herr Andre is much like this, except that its cylinder is only three inches in diameter and that it is forced on the stone not with weights, but with a lower cylinder that presses upwards. It prints fast, like the other, but does not possess enough power.
In conclusion, I must remark that the concentration of ideas caused by writing this chapter has led me to begin experiments toward making a lithographic press which shall leave nothing to be desired. As soon as my affairs permit, I shall execute this on a large scale, and if the result fulfills my hopes, it will be a pleasure to describe it accurately to all friends of my art, or to furnish them models at cost.
