A "dry point" plate is produced by drawing on a copper plate with a steel or diamond point, and without biting by acid. The lines are cut into the copper and a burr thrown up which holds the ink in printing, and produces a soft, velvety line. The method of printing such a plate is similar to that of an etching, but the possibilities are not as great in the printing, as they rest to a greater extent upon the work of the artist. A great depth of color, producing wonderfully rich effects, can be obtained and the finer lines can be made much more delicate than by any other method.
The printing of intaglio plates in color flourished for a short period in the latter portion of the eighteenth century, and the best prints of that time now in existence are of rare beauty and bring enormous prices. The process, now almost a memory, is a costly one, and this prevents its use in book ill.u.s.tration excepting for volumes which command a very high price. This kind of printing requires the plate to be actually painted by hand with inks of such colors as the picture may require, and the painting has to be repeated for every impression that is taken. The colors are put on with a "dole,"--a small piece of muslin turned to a point,--and great care must be taken that they do not overlap, or run into, each other. As each color is placed, the plate is wiped clean with rags as already described, and when all the colors have been properly placed, the plate is pulled through the press in the same manner as in ordinary printing.
The successful printer of color plates must be a rare artist or else work under the direction of an artist. Little of this work is now done except in Paris and Vienna, and the limited number of color plates of this kind used for book ill.u.s.tration in this country does not warrant the time and expense necessary to train printers capable of doing the work. Even English plates are usually sent to Paris to be printed.
It is difficult to describe the work of what is termed artistic printing. Every plate is a subject to be treated by itself, and no hard and fast rule can be applied. It is really a matter of artistic feeling, and to revert to the simile of the angler, one cannot explain how a trout should be played, but can only say that it depends on the fish, the water, and the circ.u.mstances. A fisherman can _show_ you, if you are on the spot, and so can the printer.
THE GELATINE PROCESS
By Emil Jacobi.
Of the many photo-mechanical processes which have come into existence in recent years, the photo-gelatine, next to the half-tone process, has shown the greatest adaptability for practical use in art and commerce.
Whatever the name may be,--Collotype, Artotype, Albertype, Phototype, or Carbon-gravure,--the principle is the same; an impression is made in printer"s ink from a photo-chemically produced design on a gelatine surface, either on the hand-press or on a power cylinder press similar to that used in lithographic printing.
There is hardly any process which is more capable of producing fine works of art. It is the only true method for reproducing, in the full sense of the word, an etching, engraving, a drawing in pen and ink, an aquarelle, a painting, or objects from nature. The depth and richness of tone of an engraving, the delicate tints of an aquarelle or india-ink sketch, and the sharpness of the lines of an etching or pen sketch can be reproduced with such fidelity that it is often impossible to distinguish the copy from the original, and this is achieved the more easily as the printing can be done in any color and on any material, be it paper, parchment, leather, or textile goods.
Another great advantage of a gelatine print is its inalterability and durability, no chemicals being employed in transferring the picture to the paper. The picture itself being formed by solid pigments, such as are used in printer"s ink or painter"s colors, there is no possibility of its fading or changing color, which cannot be said even of platino prints, at present considered the most lasting of all photo-chemical processes.
Like all new inventions, the photo-gelatine process, in its early stages, had to undergo severe trials, and for some years almost disappeared from public view, after many failures precipitated through unscrupulous promoters and inefficient persons who claimed impossibilities for the new process. It took years of patience and perseverance to regain the lost ground and overcome the opposition of those who had suffered by the failure of this process to produce the promised results; but at present it is, in Europe, one of the methods in most general use for ill.u.s.trating, and in this country it is making steady progress and rapidly finding favor.
The process, simple as it may seem to the casual observer, requires, more than any other photo-mechanical process, skilled hands in its different manipulations to keep it up to the standard of perfection.
The following short description will give the uninitiated sufficient enlightenment to think and speak intelligently about it.
The foundation or starting point, as of all the other photo-mechanical processes, is a photographic negative; that is, a picture on gla.s.s or some other transparent substance, in which the light parts of the picture appear dark, and the dark parts light in transparency, graduated according to the different shades of tone in the original.
The next and most prominent feature is the printing plate. A perfectly even gla.s.s, copper, or zinc plate is covered on the surface with a solution of fine gelatine and bichromate of pota.s.sium, and dried. This printing plate is then placed under a negative and exposed to the light. The action of the light on the bichromated gelatine forms the basis of this process. In proportion to the graduated density of the negative, the light acts more or less on the bichromated gelatine, rendering the latter, in proportion, insoluble and hardening it. After sufficient exposure the plate is washed out in water to eliminate the bichromate not acted upon by the light, and is then actually ready for the press.
If the printing is to be done on a hand press, a lithographic leather roller is charged with printer"s ink, and the plate, which has been fastened on a suitable bed-plate in the press, is rolled up while it is still moist. Those parts of the plate which were acted upon by the light and hardened, repel the water and take up the ink, and thus all the graduating tones, up to the high lights or white parts, which have not been affected by the light, will take the ink proportionately. The white parts of the picture, where the light did not act upon the gelatine during the exposure under the negative, retain the natural property of gelatine to absorb water, and consequently repel the ink altogether.
From the foregoing it will be easy to understand that a certain degree of moisture in the plate is necessary to get a correct impression.
After the leather roller, a composition roller, such as is used in typographical processes, is employed to make the ink smooth and give the fine details not obtainable from the rough surface of a leather roller. A sheet of paper is then placed upon the plate and by pressure the ink is transferred from the plate to the paper.
The printing, in former years, could only be done on hand presses; but with the introduction of improved power presses especially adapted to it the process itself has been so perfected that the finest work can be executed on them, at the same time insuring greater evenness and increased quant.i.ty of production, and also admitting the use of larger plates than would be possible on a hand press.
The prevailing impression, whenever machinery is employed to supersede hand-work, is that the production is increased to such an extent as to reduce the cost to a minimum, but in the gelatine printing process, even with the aid of power presses, the rapidity of printing is far behind the possibilities of the lithographic or typographical printing press, and the process, therefore, is only applicable to works of art, and the better grade of ill.u.s.trations in literary and commercial publications.
The lesser rapidity of production and the greater cost is balanced by the quality, where this item comes into consideration; and where only small editions are required, even the cost compares favorably with other methods, as the initial cost of preparing the printing plate is small compared with the cost of photogravure or the better cla.s.s of half-tone plate. It is only in cases of large editions of many thousands that the advantage of rapid printing reduces the cost of the initial expense. But fine art publications and ill.u.s.trations will never be used in very large quant.i.ties, and, therefore, there is a large field for the photo-gelatine process in this country, where it is as yet so little used. In France, Germany, and Austria there are dozens of establishments which employ ten or more power presses for photo-gelatine work, while here only within the last few years has the process been sufficiently appreciated to warrant the introduction of a few steam presses; and these have to be imported from abroad at a high rate of duty, as the present demand for the presses does not make it advisable for our domestic press builders to invest in their construction, especially after an isolated attempt in that line, misguided by inexperienced and unpractical men, which turned out to be a total failure.
Notwithstanding all these difficulties and obstacles, it is a fact that the photo-gelatine process has gained ground sufficiently to indicate a prosperous future, as its products are becoming more widely known and appreciated.
LITHOGRAPHY
By Charles Wilhelms.
As an embellishment to the modern book, chromo-lithographed ill.u.s.trations are quite popular and in some cases absolutely necessary, being not only attractive, but conveying an accurate idea of the color as well as the form of the object ill.u.s.trated. Although the ill.u.s.tration is nothing more than a colored print, it may be a revelation to some when they learn of the numerous details incidental to its production.
It may not be generally known, and yet of sufficient interest to the reader to state that the art of lithography, or surface printing, was invented accidentally. The inventor, Aloys Senefelder, had been engaged for years endeavoring to find some process for etching copper plates as a subst.i.tute for typographic printing plates; and the piece of stone (of a kind now known as Solenhofen lithographic stone), which eventually led him to the discovery of lithography had been used by him as a slab upon which he had been accustomed to grind his printing ink. The materials which he used for his acid-resisting mixture while etching his copper plates were beeswax, soap, and lampblack, and in selecting these materials he accidentally invented the basis for all crayons or lithographic "tusche" or inks, now used so extensively for drawing on stone. It seems that Senefelder finally became thoroughly disheartened about his etched copper plates, mainly owing to the great expense and labor connected with their production, and was about to discontinue his efforts when the idea occurred to him to experiment with the stone which he had used as an ink slab for so many months, treating it in the same manner as the copper plates.
He knew that the calcareous stone was easily affected by acid and that he could protect its surface against it by a layer of wax. After polishing the surface of the stone and coating it with a slight layer of wax, he made his drawing with a pointed tool, laying bare the surface of the stone where he desired the engraving. Then applying the acid and removing the remaining wax, he filled the etched lines with printing ink, cleaned the surface of the stone with water, and was enabled to obtain an impression on paper from it. This manner of treating a stone has been employed by vignette engravers for many years, but of late has become obsolete. The result gave encouragement to Senefelder and induced him to renew his experiments, when he was accidentally led a step farther in the direction of surface or chemical printing.
Senefelder had just ground and polished a stone, when his mother entered the room and asked him to take a memorandum of some clothes which she was about to send away to be laundered. Having neither paper nor ink at hand, he hastily wrote the items with a pen, dipped in his acid-resisting mixture, upon the stone which had just been polished.
When he afterwards started to wipe the writing from the stone, it occurred to him that it might be possible to reverse his process by etching the surface of the stone, leaving the writing or drawing in relief, which could be printed from in the same manner as from type.
He was fairly successful in this, and after many disappointments and much hardship, he eventually succeeded in interesting a capitalist, with whose a.s.sistance he was enabled to establish his new relief stone process on a commercial basis.
The process, however, was at best only an imperfect one, and it seems strange that the final discovery of surface or lithographic printing should have been so long delayed, when Senefelder was in reality so near it, when he first poured the acid over the stone containing his laundry memorandum. If he had instantly washed off the acid and cleaned the surface of the stone with water, he might have proceeded to print thousands of impressions by simply keeping the surface of the stone moist while pa.s.sing the ink roller or dabber over it, then drying and taking an impression, and repeating this operation indefinitely. It is not surprising, therefore, that a man of such persistence and capability as Senefelder should eventually discover the best method for drawing and printing from stone; for it is a fact that, since he perfected his invention, more than a hundred years ago, it has been hardly possible to improve on his methods, so completely did he cover the entire field of manipulation in this direction.
Continuing his experiments, Senefelder finally found that the calcareous stone absorbed and held grease, and that it just as readily absorbed water, where the surface was exposed and clean; that any design drawn or transferred with a greasy crayon or ink upon a cleanly polished stone would be firmly held, after being slightly etched; and that after such a stone had been moistened, it could be inked with rollers, the ink adhering only to the greasy matter const.i.tuting the design (although it did not stand out in the relief) and that the ink rollers would not s.m.u.t the stone, the ink being repelled by the water or moisture covering its surface. Upon this principle of chemical affinity, the adherence of greasy substances to each other and the mutual antipathy of grease and water, the art of lithographic printing is based.
The methods or processes now employed in reproducing oil-paintings, colored photographs, or water-colors by lithography are numerous, and require great skill and experience, not only on the part of the lithographic artist, but also on the part of the printer. Photography has of late years been used to a great extent in creating the basis of the color plates, to be afterwards perfected by the manipulation of the experienced chromo-lithographer.
To insure a satisfactory result the first essential is, of course, a good original, which can be made in water-color, oil, or pastel. The number of printings to be employed should be predetermined and a color scale adopted. The lithographer must carefully a.n.a.lyze the original painting, making his calculations as to the best way of obtaining the desired color effects by a judicious selection and use of his colors, and the superimposing of one printing over the other, so as to obtain true color values. It must be remembered that, while the average painter has an unlimited variety of pigments at his disposal, the lithographer is in this respect very much at a disadvantage, not usually having more than from six to fourteen colors with which to produce a facsimile of the original.
The first step is the making of the so-called key-plate. A piece of gelatine is laid on the original, which is, let us say by way of ill.u.s.tration, a water-color to be reproduced in ten printings, and a careful tracing of the original is made by scratching, with an engraving needle, the outline of each wash or touch of color composing the picture. This being completed, the lithographic ink (tusche) or transfer ink is carefully rubbed into the tracing, which is laid face down on a polished lithographic stone, slightly moistened, and pa.s.sed through a hand press; thereby transferring the ink from the engraved lines to the polished surface of the stone. The design on the stone is then rolled in with black printing ink and etched, thus enabling the lithographer to take the necessary ten impressions of the key-plate.
These, in their turn, are again transferred to as many lithographic stones. This is accomplished by dusting the impressions with a red powder, which adheres only to the design printed on the sheet. The powdered outline design is then transferred to the surface of the stone by pa.s.sing both through a hand press. The key has been previously provided with register marks (a short horizontal line intersected by a vertical one) at top, bottom, and both sides. These are of the utmost importance to the prover, and finally to the transferrer, who prepares the work for the press, as without them it would be impossible to register one color over the other in its proper place. At any stage of the process, the register marks of all ten colors, which have been made in succession on a single sheet of paper, should coincide precisely and appear as a single mark in the form of a small cross.
The lithographer now has before him the ten stones, each stamped with the identical network of lines in red chalk representing his key. He proceeds to draw each color-plate successively, at all times adhering closely to the red chalk outlines, filling in with tusche where full strength of the color is required and using lithographic crayon or the stipple process to reproduce the various gradations of this color in order to secure the full color value of each printing. The register marks are ruled in on each stone corresponding to those on the key, so that the prover or printer has these marks in the same identical position on each and every color as a guide for register.
As each stone is finished it is etched; that is, treated with a weak solution of nitric acid and gum-water, in order to remove all accidental traces of sc.u.m from its surface, and to prepare it for printing. Then proofs are made, which serve as a guide to the lithographer during the progress of his work, and finally as a guide to the transferrer and to the printer. The proving is done on a hand press, and it is here that we have our first glimpse of chemical printing, which, notwithstanding its simplicity, seems so mysterious to one uninitiated in its secrets.
The writer recollects his own first experience. A stone had just been placed fresh from the etching trough in the bed of the press, when, to his amazement, the prover deliberately proceeded to eliminate every trace of the drawing with a sponge saturated with turpentine. After drying the stone by means of a fan, he pa.s.sed over the surface a sponge soaked in water, then applied black ink with a roller, when behold, the drawing was restored in its entirety. The solution is very simple: the greasy matter is absorbed and held by the stone and in its turn repels water and attracts grease.
An impression is made with black printing ink on paper by pa.s.sing it through the hand press. The black impression approved of by the lithographer, the stone is again cleaned with turpentine and proved in the color required, and so with each color-plate, until the proof is complete. When photography is employed, the half-tone negative takes the place of the key. Prints are made from a reversed negative on the sensitized surface of the stone, or on as many stones as the color-plates require, and then manipulated by the lithographer, who adds or modifies strength with his "tusche" or crayon, and sc.r.a.pes or washes out lights where necessary. The various modes of procedure are too diverse to enter into here, but it may be well to mention that the princ.i.p.al ones are the alb.u.men, the asphaltum, and finally the three-color process, the latter differing but little as far as the artistic part of the work is concerned from that employed for making relief printing plates for the typographic press.
The original drawing plates, or stones, are not used to print from direct unless the edition be very small. Just as the typographic printer uses electrotypes in place of the original type or cuts, the lithographer makes transfers from the original stones to print his edition and carefully preserves the original stones for future editions. The transfers are prepared in a very simple manner. The original stones are rolled over with a specially prepared transfer ink, and impressions are taken from them on a paper, known under the name of transfer paper, coated with a sizing of starch, flour, and glycerine. By printing from the original, only one copy can be produced at each impression, whereas by using transfers a number of copies of the original can be printed at one impression. For example, if the picture measures 8 10 inches of paper, a transfer can be made containing fifteen copies on one sheet measuring 30 40 inches. In this case fifteen impressions are made from the key-plate as well as from each of the color-plates, on the paper, and with the ink described above.
The first transfer to be made is that of the key-plate. The fifteen impressions are laid in their proper positions on a sheet of paper of the required size, and are held in position on same by indentations made with a dull-pointed steel tool. The sheet is laid face down upon a cleanly polished stone, which is then repeatedly pulled through a hand press until all the ink has been transferred from the paper to the surface of the stone. The transfer paper still adhering to the stone is then moistened and washed off the stone, leaving the design completely transferred to the stone. A slight solution of gum arabic and water is then applied, the stone washed clean, and after being repeatedly rolled in with printing ink and etched, is ready for printing. An impression is then made in the usual manner from this key-transfer, which impression is coated with a solution of sh.e.l.lac.
This is done for the purpose of rendering it impervious to the effect of the atmosphere, thus insuring against its stretching or shrinking.
Upon this varnished key-sheet all subsequent transfer impressions of the ten colors are "stuck up," to use the technical term, and transferred to stone in the same manner as is employed in the making of the key-transfer. The register marks serve as a guide in "sticking up" the separate transfer impressions and insure an accurate register of the colors laid over each other during the process of printing. New register marks are placed upon the key-transfer at top, bottom, and sides similar to those on the original (which are removed from the transfer), and these new marks now appear on all color transfers to serve as a guide to the steam-press printer in printing his edition.
He likewise uses the hand-press proofs of the picture as a guide in mixing his inks.
The lithographic power printing press is constructed on the same general principle as the ordinary typographic press, excepting that it is provided with an apparatus for moistening the stone previous to the application of the ink rollers. The stone containing the design is placed in the bed of the press, and the moisture, as well as the ink, is applied by means of rollers similar to those used in the typographic printing press. All the ten colors are now successively printed from the transfers on a steam press, and if it is a perfect job, the pictures can be cut to size and delivered to the publisher.
At present the c.u.mbrous stone and the slow-moving flat-bed press are being supplanted by the light and pliable aluminum plates and the fast-moving rotary presses. The aluminum plate has all the requisites for the highest grades of lithographic or surface printing, and the rotary press is beyond doubt a vast improvement over the flat-bed press, not only as to speed, but also as to the quality and uniformity of its product. The mode of procedure in making transfers to aluminum plates is much the same as that employed in making transfers to stone.
The pliability of the aluminum plate and the ease with which it can be adjusted to a printing cylinder has resulted in the successful introduction and use of two-and three-color lithographic rotary presses, printing at one operation two or three colors. It has been demonstrated that the result is fully equal to that obtained from the single-color press, provided good judgment be used as to the succession of the colors or printings. This marks a new epoch in the art of lithography and enables it to compete with the typographic three-color process, which has been making such wonderful progress during the last five years, and at one time seriously threatened lithography as a medium for the reproduction of certain cla.s.ses of colored ill.u.s.trations.
Our experience teaches us, however, that the surface or lithographic and the relief or typographic method will never seriously interfere with each other, but on the contrary by actively competing in all matter relating to the reproductive art will continue to improve their respective methods, and thus enable them to satisfy the continually increasing demands on the part of the public for colored ill.u.s.trations, not only as to the quant.i.ty but particularly as to the quality thereof.
COVER DESIGNING