Lithography (Gr. lithos, 'a stone,' and graphein, 'to write'), the art of printing from stone, and one of the most important of the reproductive arts, was invented in 1796 by Aloys Senefelder (1771-1834). In that year a piece of music—Senefelder's first work—was printed from the stone, and in 1800 he patented his invention in Bavaria, most of the German states, and Austria. Afterwards he opened establishments in London and Paris, but did not succeed very well. The great secrecy and jealousy with which the new art was guarded by its patentees prevented progress being made, and it was not till many years afterwards that their complicated manipulation became sufficiently simplified for the rapid advance which then became possible. Senefelder, on whom the king of Bavaria settled a pension, lived to see his invention brought to complete perfection.
The principles on which lithography is founded are (1) the strong adhesion of greasy substances to calcareous stone; (2) the affinity of one greasy body for another, and their antipathy to water; (3) the facility with which calcareous stone imbibes water. It follows that, if a greasy line be drawn on a prepared stone, its adhesion is such that it can only be erased by entirely removing the surface of the stone so far as the grease has penetrated. If water be put on the surface of the stone it remains on those parts not covered with grease; a roller charged with greasy ink may then be passed over the stone, the ink adhering to the greased portions, while the parts wet with water will repel the ink and remain clean. A piece of paper put on the stone, if pressure be applied, will receive an impression in ink of the greasy line. The covering of the stone with a solution of gum-arabic (to be afterwards described) is an almost indispensable aid to the water in resisting the ink.
There are various methods employed in lithography—drawing on stone with pen or brush with liquid ink; drawing on paper, and transferring to stone; engraving on stone; drawing on stone with crayons or solid ink, transferring from engraved plates or woodcuts, &c. These differ only in the manner of applying the greased drawings to the surface of the stone. The printing from them is in nearly all cases identical.
The Stones.—The immense quarries of Solenhofen in Bavaria furnish the best stones; others of inferior quality are obtained in France and Italy. The stones are composed of lime, clay, and siliceous earth, and are of various hues, from a pale yellowish-white to a light buff, reddish, pearl-gray, blue, and greenish colour. Those of a uniform gray colour are the best. They are found in beds, commencing with layers of the thickness of paper; the thickness required for printing-stones being from about 2 to 4 or 5 inches. When in the quarry they are soft and easily cut to any required size. They are afterwards ground face to face with sand and water, and when quite level polished with pumice-stone, and finally with smooth polishing stone. Sheets of zinc faced with thin coatings of artificial stone have been introduced, but not as yet with much success.
The writing and drawing inks and crayons are composed of lard, hard soap, white wax, shell-lac, Venetian turpentine, carbonate of soda, and Paris black. The proportions used and the methods of manufacture vary considerably. All descriptions can be purchased ready prepared. The greasy ingredients are the important parts; the black is only added to enable the artist to see the effect he is producing as he goes on.
Writing or drawing on stone is performed with a fine pen or brush, or a ruling pen for straight lines. The ink is rubbed down with a little water and under gentle heat, in the same manner as China ink, and the subject may be traced as for a drawing on paper. Great care is necessary in handling the stone, as its affinity for grease is so keen that a finger-mark would develop into a black blot in printing. When the drawing is finished it is covered over with a solution of gum-arabic in water. This gumming fills up the pores of the stone on the undrawn parts, and prevents the greasy lines of the drawing from spreading. The stone is then removed to the printing-press and prepared for printing. The gum is first washed off with clean water, enough remaining in the pores of the stone, however, to assist the water to resist the ink in the subsequent printing. The stone is then damped with a canvas cloth, and a roller (made of wood or iron, covered with one or two thicknesses of flannel and an outer covering of fine leather) charged with printing-ink is passed over the stone till every part of the drawing is thoroughly inked. Any accidental grease or finger-marks will now become visible, and must be removed with acid, scraping with a knife, or polishing with polishing stone. When the drawing is made satisfactory the stone is washed over with a weak solution of nitric acid in gum-water. This etching, as it is called, is a very important operation. If applied too strong the acid would remove the drawing completely from the stone; but when diluted to the proper strength it gently eats away the surface of the bare parts of the stone, opening up the pores for the better reception of the gum to be afterwards applied, thoroughly cleans it from grease-soils, and sharpens the lines of the drawing. When the stone is sufficiently etched the acid is washed off and another coating of gum applied; when this is dry it is again washed off, and, usually, to clean the stone from the drawing-ink, the surface is washed with turpentine. For all that can be now seen on the stone the work is quite lost; but it is only the black ink that is washed off; the grease lines are in the stone, which is all that is necessary. The stone is now damped with a cloth and inked with a roller till all the drawing is black again; a piece of paper is placed on the top, passed through the press, and when taken off has received an impression of the drawing. The damping and inking is repeated for every impression, and when the stone is put away or left for a time it is, for preservation, covered with the indispensable gum, which is again washed off when printing is resumed. The ink for black printing is composed of Paris black, ground up with varnish made from boiled linseed-oil.
Writings and drawings made on prepared paper and transferred to stone for printing are, perhaps, the most important items in general lithographic work. The transfer paper is prepared on one side with a coating of isinglass, flake-white, and gamboge, and afterwards smoothed by passing several times through a press over a heated stone. The writing or drawing is made on this preparation with a pen or fine brush with the lithographic transfer ink, and when finished is transferred to the stone in the following manner. The paper is put for a few minutes between damped blotting-paper. A warmed polished stone is put in the press, the paper is placed with the coated side upon it, and passed several times through the press, after which the paper is damped with water and gently rubbed with the fingers till it comes easily off, leaving the drawing adhering to the stone. The stone is gummed over and proceeded with as already described. After the first inking-up, and before etching, any defects in the transfer can be touched up with a pen or brush. In France and some other countries this class of work, however, is generally either directly drawn or engraved on the stone.
Fresh impressions of lithographs, of engravings on wood, steel, or copper, and of letterpress may be transferred to and printed from the stone by the above process, the paper used being prepared with a special composition, and the ink a mixture of the writing and printing inks. Many subjects, such as music titles, &c., are engraved cheaply on zinc, expressly to be transferred to stone. When the design is small and required in large numbers, it may be transferred many times on one stone, and many printed on one sheet of paper at every impression.
Engraving on stone, so called, is another method of putting a drawing on stone, and is as follows. A polished stone is covered with a coating of gum slightly coloured; this is afterwards roughly washed off, leaving only a very thin film of the gum, which can be easily cut through. On this ground the drawing is executed with etching-points of diamond and steel of various breadths, exactly as in etching, the surface of the stone being cut through the gum in making the lines. When the drawing is finished any greasy matter is rubbed into the lines and allowed to remain an hour or two till the stone has imbibed enough at the lines. The gum is then washed off, and the stone damped and inked and proceeded with as above, except that engraved stones are generally inked with a dauber—i.e. a piece of wood covered with one or two pieces of flannel, with which the ink is rubbed into the lines.
The following modification of this process is very useful when a photograph or drawing has to be copied in line for the stone. A thin sheet of gelatine is placed over the subject to be copied, and, it being transparent, a careful drawing may be made on it with etching-points. When finished, lithographic ink is rubbed into the lines and the gelatine placed on the stone and the drawing transferred by passing through the press. The weak point of this process is that the gelatine is apt to warp on the stone and spoil the transfer; in which case the drawing is lost.
Chalk-drawings were, before the invention of the steam lithographic press, and still on rare occasions are, drawn on grained stones. The grain, coarse or fine as required, is imparted to the stone by grinding with sand of varying degrees of fineness. The drawing is made on the stone with lithographic crayons in the same manner as the ordinary drawing chalks on ordinary crayon-paper; when finished it is proceeded with as before. Very beautiful work can be produced in this way; but as, owing to various causes which are too technical for our space, the grained stone cannot be printed at the steam-machine, and hand-press printing is too expensive for modern requirements, such work is now almost invariably executed by the grained-paper process. A sheet of copper or other metal is grained on the surface by aquatint, stipple, or ruling-machine; paper, coated with a white transferring ground, is passed through a press on the face of the prepared plate, becomes impressed with the grain, and may be drawn on with lithographic chalks in the same way as a grained stone. This drawing is transferred to a flat or polished stone in the same manner as writing or pen drawing, and printed in any lithographic press. Very good work is produced by this process, but the result of the somewhat artificial grain of the copper-plate is inferior to the beautiful grain of the ground stone. In the United States drawings are made on grained stones and impressions transferred to flat stones for printing; but this process has not found much favour in Great Britain.
Photo-lithography is a very useful method of reproducing in any size, for stone printing, existing drawings, such as architects' plans, maps, &c. A photo-negative of the required size is taken from the drawing to be reproduced, and is exposed to light over a thin film of bichromatised gelatine on paper. The paper, after being soaked in water, which takes out the bichromate unaltered by the light, is stretched on a sheet of glass and carefully inked with a velvet roller. The ink only adheres to the parts rendered insoluble by the light, and which have remained dry during the soaking, and leaves the soluble parts, which are wet, quite clean. This is transferred to stone in the ordinary manner.
Chrono-lithography is the most beautiful of all the methods of printing from stone. The object being to produce, as nearly as possible, fac-similes of pictures in colour, it is necessary to employ a number of stones, in some cases as many as twenty or thirty, each printing a separate tint, to produce the infinite variety of colour in a finished colour-drawing. The usual method of procedure is as follows. A careful outline of the entire design is drawn on, or transferred to, a stone; from this, called the key, as many copies are printed as there are colour-stones required. These impressions are dusted with dry black or raddle, and, being set off on the colour-stones, form guides to the artist in drawing in the various colours; after which the key lines can be washed away with water. On one of these stones the general effect of the picture is sometimes drawn, and this, printed in a neutral gray, forms the basis of the finished print. The other stones are drawn separately to correspond with the different colours required to produce the necessary effect. It will be easily understood that in arranging the various colours with their varying degrees of depth on the different stones, the proper amount of force to be given to each, and the effect likely to be produced by printing one tint over another, have to be considered, and give scope for a great deal of professional skill. There are many different methods of drawing the tints on the stone which are too technical for our limits. The finest work is done by stipple, drawn by hand with a fine brush, a method in which French and German artists on stone are very skilful. The colour stones are printed in the manner already described, except that coloured inks are used instead of black. The different colours, varying in number from four or five to twenty or thirty, being printed by separate impressions on the same paper, it is obvious that great care is necessary to see that every impression is exactly fitted to the others, or exactly registered, as it is called. Several mechanical appliances are used to secure this exactness. When the necessary number of impressions have been printed and the stone has to be cleaned for another subject, the surface must be laboriously polished down till every vestige of grease is removed.
Such is a brief outline of the different methods employed in lithography, but each method is capable of infinite number of variations in the hands of different operators.
Lithographic presses vary as much in construction as those for the letterpress. The hand-press is very simple. The stone is placed on a movable table, and a tympan, an iron frame covered with leather, folds down over the paper when placed on the stone. It is then rolled under the scraper, generally a piece of boxwood fixed in an upright, which applies the pressure. The damping and inking are done by hand.
The first self-acting lithographic machine, introduced into Britain by Sichel of Berlin and Vienna, failed from the fact that it was constructed, like the hand-press, with a scraper arrangement for the impression. This produced too much friction, rendering speed dangerous, and work difficult to keep on the stone; and it was not till about 1860 that the machine as at present in use, with a cylinder for the pressure, was introduced from France. It is somewhat an adaptation of the letterpress single-cylinder machine (see PRINTING), and a very brief description will suffice. The stone is placed on a movable bed, which can be raised or lowered according to the thickness of the stone. The sheet is fed in at the top of the cylinder, whence a gripper arrangement leads it over the stone. At one end are the damping-rollers, which are covered with some soft absorbent fabric; and at the other the inking-rollers, covered with the finest French leather, with inking-table, duct, and distributors. The stone passes first under the dampers, then to the inking-rollers, thence back to the cylinder to print the impression, and so on ad infinitum.
Zincography, the invention of Eberhard of Bavaria, is an application of lithography to zinc plates instead of stones, with some necessary modification of the etching and printing. Its only advantage is in connection with very large subjects, as the zinc is more portable and less liable to breakage than stone.
See G. A. Audsley, Chrono-lithography, a popular treatise (44 plates), and W. D. Richmond, The Grammar of Lithography and Colour and Colour Printing as applied to Lithography (6th ed. 1887), both in Wyman's Techn. Series.