CHAPTER VI.

HINTS FROM ALL SOURCES.

Although the number increases almost every week, there are but few persons who understand photo-reproductive processes in all their details. Those who do, have been so chary of giving of what they know, that our literature on the subject is very scanty indeed. Consequently, as all the hints that are obtainable are very welcome, I have collated a few from various sources, and make a mosaics of them here for the general good.

Every would-be photo-engraver, if he is not already a skilled photographer, should obtain and study a good photographic text-book. If he proposes to make his own drawings, he should also obtain Burnet’s _Essays on Art_. The first will not only teach the best formula for the production of negatives, but it will also enjoin the importance of being careful, cleanly, and exact in all the manipulations. The second will teach how to draw according to the best rules of art. Remember always, the old injunction, _whatever you are, be best_! After the regular photographic manipulations are well looked after, the preparation of the drawing should have attention.—EDWARD L. WILSON.

AS TO THE DRAWING.

There are two separate and distinct styles of drawing for reproductive purposes, whether the artistic engraver be employed, or any of the means of automatic engraving be used. These two methods are technically known respectively as _fac simile_ drawing, and drawing in wash. The former consists in the sole employment of lines, in which the shading is to be produced as well as the outline of a picture. Every line and mark that is subsequently to appear in the engraving must be traced in the original. This description of drawing is applicable to wood engraving, to line engraving upon copper or steel, as well as to all the methods for automatically producing blocks for relief printing. The line method is also universally adopted by etchers in _intaglio_.

Successfully to prepare drawings for photographic reproduction it is essential that some knowledge should be possessed of the fundamental principles of |95| photography, as well as an acquaintance with the capabilities of the particular process of production which is to be employed. Thus, the material upon which the drawing is to be made should be of such a character as will yield a strong and well-defined contrast to the lines of the drawing; while the pigment employed for the drawing should be as black as can be procured. White Bristol board of fine surface, and the best India ink meet these conditions. A blue-black does not form a desirable drawing medium, but the introduction of red or orange into the composition should serve to intensify the photographic image. To draw upon a dark orange-colored paper with a pale blue-gray ink would be simply to disregard all photographic principles, for the photographic value of the paper and of the ink would be nearly equal, and the drawing would consequently be lost.

Uniformity of color in the drawing is also desirable, and the artist should resist the natural tendency to express distance and to produce his effects by diminishing the intensity of color in parts of his picture. From a drawing uniform in color a satisfactory negative is obtained; but, in the other case, the photographer must estimate an average duration of exposure, and will rarely escape the dilemma of some portions being overexposed while others are comparatively undeveloped. This theory receives illustration from the fact that very good subdued effects can be obtained from well-executed pencil drawings, where this uniformity of color is preserved. A longer exposure may be required, but every part of the picture will be equally developed.

To return to the matter of the paper used, color is not the only important consideration. If the surface of the paper is irregular and coarse in texture, such as painters in water-color delight in, good results must not be expected. A negative, taken in the ordinary way from a drawing made on such material, would inevitably reproduce all the inequalities of the texture of the paper, to the manifest injury of the more delicate parts of the drawing. In reproductions from old prints or printed books, the conditions and character of the paper present some of the greatest difficulties with which the photographer has to contend. The ridges in the surface of the paper cast shadows which are too faithfully reproduced in the negative. The employment of a diffusive rather than a direct light is the usual remedy, but the best way of dealing with the difficulty is that employed in the studio of the Autotype Company. The original is laid upon the floor under a strong light, and the camera set at an angle of forty-five degrees.

Mr. Alfred Dawson informs me that he inclines to the opinion, founded upon |96| his extensive experience and untiring experiment, that it is desirable to get rid of the surface of the paper altogether, by covering it with a substance similar to an enamel.

In conclusion, the conditions required in the successful preparation of drawings for photographic reproduction, may be thus briefly summarized: That a sufficient photographic contrast should exist between the pigment employed and the material upon which the drawing is made; that a paper should be selected which is smooth and without water-mark, and white; that the drawing material may be pencil or ink, in which blue is not a component.—JAMES S. HODGSON.

FADING OUT THE PHOTOGRAPH.

For newspaper line work excellent results may be obtained by drawing over a photograph, and then fading out the photographic parts not wanted. There are several methods, but the following is the most simple and the easiest to manage: Make a weak solution of cyanide of potassium and add a flake or two of iodine. When the drawing is made with water-proof ink and on a photograph printed upon bromo-gelatine paper the above solution flowed over it will at once cause such portions of the image as have not been drawn upon with the ink, to fade away and leave nothing but a fine ink sketch against a perfectly white background.—ROBERTS & FELLOWS.

THE REVERSAL OF DRAWINGS (NEGATIVE PRINTING).

This very simple and very safe method is to be recommended especially for advertisements in papers and for titles of books, and can be made both by aid of photography (by a transparency) and without it, in the following manner:

Make a copy, on copy-paper, of the drawing to be reversed, using an ink of gum, glycerine, and aniline, and transfer it carefully, without using too much water, when loosening. Dry the plate, and pour over it a solution of 1 part of asphaltum, 1 part Venetian turpentine, in 18 parts benzole; then allow to dry upon a plate. Place the plate into a weak soda solution, and develop with a fine pad of cotton, till the drawing stands clear. Ordinarily I employ the following method: A plate prepared for transfer is uniformly cleansed with gallic acid and then coated with gum, as in the case of blackening a transferred drawing, while both solutions are left to dry spontaneously. This done, the coating of gum and gallic acid is thoroughly washed off, and the plate is carefully dried and gently warmed. The transferred drawing must be made on |97| paper with an easily soluble layer composed as follows: dissolve 100 grammes of wheat starch—_i. e._, starch _made_ of wheat—in 400 c.cm. of rain-water; raise 1 litre of water to boiling and dissolve therein: 50 grammes of common salt, 75 grammes of glycerine, 50 grammes of gelatine, and 25 grammes of molasses; when these are well dissolved and taken up, add slowly the wheat-starch, stirring continually; then allow to boil a short time so that we may dissolve it without an excess of water after the ordinary transfer of the picture. When this has been done, we wash it again with a soft brush and water, dry, dust twice, and burn in thoroughly with asphaltum. Place the plate in a very weak bath of nitric acid (10 cubic centimetres of acid to 1 litre of water), and rock it lightly for about two minutes until the zinc changes color. Then wash, dry, and warm.

The combination of gum and gallic acid is broken up by this etching in all those places which were not protected through the transferred drawing, and the latter itself, in the subsequent blackening with chemical India-ink, forms the coating and protection against a combination of the zinc below. It is best to blacken it with a brush and to warm the plate until the ink has become dry. Now moisten again with gallic acid and gum, wash the plate (without great pressure) with spirits of turpentine, rub on more of the solution of gum, and blacken as usual. Practice will insure safe working by this method.—J. O. MORCH.

ETCHING APPARATUS.

It does not come within the province of this work to instruct in the preparation of inks and colors for etching or for printing, since such articles are better purchased of the dealers ready prepared. In all cases the choicest results are obtained by using the best apparatus and the purest materials. There is no economy in “getting on” with the “cheap.”

A few hints as to some of the “tools” which are found convenient in practice: For sifting the fine _resin dust_, a machine is employed, known to sieve manufacturers as “the _composition_ sieve.” It consists of the ordinary sieve, having on each side a cover with a bottom of calf skin. The sieve-bottom is made of the finest silk texture. (See Fig. 10.)

For fixing and melting-in of the drawing on metal, I use a grate made of a wooden frame with diagonal iron rods. This form is preferable to the ordinary grate, because it allows the flame free access to the metal plate. Inasmuch as the heat is strongest in the _centre_, the cross-bars protect the centre of the plate from burning and from warping. The source of heat is either an alcohol |98| lamp (Fig. 11) in which cotton soaked in alcohol is ignited (the cover shown in the drawing serves to smother the flame), or a strong gas flame (Bunsen burner). The adoption of the latter mode is advisable.

Formerly I employed a plain cast-iron heating-plate, with a gas or a petroleum flame. The zinc plate, however, being in direct contact with the hot surface, warped very much. I obviated that somewhat by covering the heating-plate with a piece of wire-gauze. The strata of hot air thus obtained between the cast-iron and the zinc plate heats the latter equally throughout, and prevents warping. Still I prefer the direct method.

For freeing the plate from resin-dust, employ a strong pair of ordinary bellows.

The table (Fig. 12) for washing the coating material from the plate consists of a heavy framework, upon which rests a wooden grate. A massive table-board is not to be recommended, as the dirty sawdust adheres to the same, while with the other it easily falls through the openings into a box, and leaves the table free and clear.

The measuring or calibre-bridge (see Fig. 7) serves to determine accurately whether the ready plates have the height of type. A rule of forty |99| centimetres will suffice for any plate. No plate should leave the workshop without having been tested as to its thickness or height on this instrument.

The zinc plane is of ordinary construction, to the bottom of which is attached a double layer of hard wood. The iron being arranged for scraping can be inserted in a position just the reverse of the ordinary plane.

The “hand-bridge” is a strong ruler, thirty centimetres long, and five centimetres wide, to the ends of which are fastened two blocks of wood one centimetre high. It serves as a support for the hand in retouching.

The rollers of the “chemigraphist,” and also the pads, are of greatest importance. For etching by the French process we need a good, rough roller, and a faultless, smooth one; for the Vienna process only the latter is needed, in addition to a smooth, tight leather ball or pad, such as was used in the art of printing prior to the introduction of rollers. A perfectly smooth surface is obtained by covering the rollers with a dryer, and allowing them to dry in the open air. A solution of shellac with camphor, applied like furniture polish, also yields a fine surface.—J. O. MORCH.

THE BEST DRYING BOX.

After bichromatizing the gelatine sheet for printing the transfer image, I proceed with the drying in a box constructed as follows:

The box has four walls or sides of cloth, or any other stuff that allows the air to pass through, and must have a solid bottom, which will allow the attachment of a heating apparatus beneath it. In this box is a cylinder which turns on its own axle, and which can be set in rotation from the outside when the box is closed. Upon this cylinder the gelatine paper, as we may call it, is placed, and the box closed. A very equalizing drying is thus obtained, by keeping the heating apparatus under the bottom of the box constantly at a steady, uniform heat. By these means, it will be noticed:

1. That an uneven running down of the chrome-layer is avoided, and uneven drying also positively prevented in consequence of the centrifugal force.

2. That the drying by the draft of air is regulated, and at the same time the air can be driven to a more rapid current.

3. That the grain formed by this extraordinary method is unusually perfect, and the nature of the grain more pleasing to the eye than when formed by chlorides.

4. That, as already stated, a rolling up or an uneven drying is hereby |100| positively prevented, as the paper is placed tight around the cylinder. And now for the main advantage:

This so dried paper is ready for use, and, when exposed to light, under a negative, produces a perfect and correct picture, which, when rolled up with transfer ink and developed in water, is ready for transferring direct on to the lithographic stone, or on to a metal plate, and to be further proceeded with as usual.—EDWARD MEISSNER.

TO PRODUCE GRAIN ON A NEGATIVE.

The negative is taken, and a solid pigment of Chinese ink sprinkled on it with the Air Brush, by which it gets a wonderfully fine grain. A coarser grain is made in a similar way, by sprinkling with a knife over a tooth-brush that has been dipped in Chinese ink. The Air Brush, however, will always be found the most suitable instrument, and now a wide field for its use is opened to artists of all classes. Instead of using Chinese ink, gamboge, or any other solid and well-covering pigment may be used.

For the practical photo-engraver, lithographer, photo-lithographer, and other men of experience in photo-mechanical processes, no further explanation is required. They will at once see the _superiority_ of this process over everything that has hitherto appeared. After the information we have just given, they will all be enabled to do work by this process. It will henceforward be easy to produce photo-lithographs for lithographic printing as well as printing plates for the type press _without difficulty, in a short time, and at trifling expense_.—FRED. BUEHRING.

ON THE USE OF ACIDS.

A few hints on use of the acids will form my contribution to your work:

In order to obtain a proper resistance and firmness in the lines, it is necessary to prevent the acid from making the base that supports them too thin, and to strengthen the base by giving the depression the form of a V, and the base itself the form of an A. The depth must be great enough in the broad blanks to prevent the roller from sinking (although there is no danger of this when the lines are close together), and thus soiling them. A useless depth between very thin sides might weaken them; but, in the process employed, the attack by the acid continues only in proportion to the width of the spaces to be excavated. |101|

These results are obtained as follows: The prepared plate bearing the design is inked with a thick ink containing a little wax, and is placed in a trough with acidulated water, which slightly attacks the metal.

The trough is mounted so as to rock, and is kept in motion by a lever actuated by a steam motor. The water moves to and fro over the entire surface, and keeps continually washing the parts that are not protected against its action. No local saturation, therefore occurs, and the continuously renewed liquid attacks the bottom as well as the sides of the hollow. The sides would soon be rendered too thin were the biting-in too long continued, and for this reason the first attack is made with great care. It is upon this that depends the sharpness of the proof. The acid used is nitric, so dilute that it is scarcely perceptible to the taste, and in the proportion of about one and a half ounces to a quart of water. The acidity is kept up by a small quantity of acid of 36°, that falls drop by drop from a bottle provided with a cock. After about a quarter of an hour, the plate is taken out, and the operation repeated as generally directed.

Remember this: At every new biting-in the acidity of the bath is increased, and, when the broad parts alone remain exposed to the attack, acid of 6° B. may be used. In this state, the zinc plate, taken from the bath and washed and dried, is treated with benzine, and then with potash, in order to remove all fatty matter. It may then be seen that the sides of the hollows do not exhibit a regular sloping surface, but a series of ridges corresponding to the series of bitings-in. As these might take the ink, and affect the purity of the lights and shades, it is necessary to remove them by an operation analogous to the first, but carried on quickly in an opposite direction. With this intent, the plate, well cleaned and heated upon the iron table, is inked while hot, with a composition formed of two parts printing ink and one part each of resin and beeswax. This ink, which can be used hot only, descends along the sides of the depressions, and when it has got half way to the bottom the plate is cooled, and the inking is renewed so as to well cover the entire surface.

It must not be believed that in practice these operations can be conducted without extreme care. A want of attention, unsuitable ink, or a too high or low temperature, may lead to the loss or poor execution of the piece. It is often objected that the lines in this style of plates have not the boldness of those produced by the graver. It is not for us to answer the question whether this is a merit or a defect; artists generally endeavor to employ paper with an irregular and granular surface, and which is far from giving such boldness; |102| and he perhaps would be poorly appreciated who should present upon glazed paper a drawing made with the pen and resembling a picture made with the graver. It is the artist’s business to produce the work such as he desires the Gilloteur to render it.—GILLOT.

MULTIPLICATION OF ZINC ETCHINGS BY GALVANIC MEANS AND BY STEREOTYPING.

Multiplication of printing-blocks by galvanoplastic, or stereotyping, is not so easy as in case of woodcuts or type. The main difficulty lies in some peculiarities of the process of etching, especially if the plate has been produced by the French method. The reproduction of a form is often impossible, since the matrix is caught on certain rough spots and then tears, thus rendering galvanoplastic reproductions imperfect.

Having very frequent opportunity of making matrices from plates, I call the etcher’s attention to several points upon which the success of the work depends. On no condition whatever may any parts of the plate be corroded from beneath, as wax or gutta-percha will invariably tear when lifting off the impression (mould).

In the second place, the bottom of the etching must be perfectly smooth, not rough; the single grades, left by etching, must be removed, and the lines must incline perfectly smooth toward the depth of the etching.

In stereotyping, the process of drying presents special difficulties, since with heat the wood warps and distorts the plate; the cold process, on the other hand, does not give equally sharp impressions. For this purpose I have mounted the plates on lead instead of on wood, and am thus enabled to get sharp impressions and to apply hot drying.

Instead of paste, I employ light magnesia; instead of oiling the plate before planing or rolling it in, I give it a high polish with stearine oil and rouge by means of a circular brush, and brush it once more with talc. Thus I am sure of success.

PREPARING ZINC PLATES ON THE PRINTER’S PRESS.

A wood-cut gives the _outrunners_ of the finest portions in a plane which runs downward; an etching, on the contrary, shows the whole engraving in one plane. According to this the _outrunners_ (the borders) often print somewhat hard, unless care is taken to alleviate this fault. This will be easy to the experienced workman. |103|

Starting from the fact that a zinc plate is easily bent, place something under the back of the _heavy_ portions in mounting, and when nailing drive the nails tight in the white lights and on the edges; thus the borders are deepened, and _print_ softer.

In this manner an experienced and practised hand can produce effects impossible in any other way.

For printing on rotary machines, galvanos are used in many places. But a zinc plate may be excellently fastened in the following manner:

Clean the back well and solder the back with soft solder, as is customary in galvanic backing. Then attach it lightly to its place on the wooden or metal block, hammer or roll in the plate without paying special attention to the zinc plate, dry the matrix, and lift it from the form. After preparing for casting take the zinc plate from the wooden block, bend it while hot, put it back into its position in the matrix, cover the edges with tissue paper and paste, dry the edges with an iron, place into the casting apparatus and cast as usual. In this manner the zinc plate (metal, cast from a matrix) is in place at exactly the height of the type and will print excellently. (The face is to be slightly oiled before fastening in the matrix, to prevent any sticking of the lead.)

As a _cover_ for the printing cylinder, I have always found paper most serviceable, although covers of English leather are also advantageous, especially for large editions. I should not recommend felt.

The rollers for printing zinc plates should be held with somewhat stronger tension than for printing of wood-engravings.

As a method of preparing, I recommend the gradating of the lights and shades, known to every intelligent machinist. Wherever possible, highly calendered paper should be used, as it gives the best results.

ETCHING WITH SULPHATE OF COPPER SOLUTION.

Nitric acid may be replaced by sulphate of copper, especially in the first periods of etching, and etching can be obtained both in a galvanic way and by easy shaking of the tray. The sulphuric acid of the copper sulphate combines with the zinc and the copper, and when liberated, precipitates as an amorphous, muddy substance.

Although this process has almost entirely fallen into disuse, the most important points are treated of below.

_The bath._—Dissolve pure copper sulphate (of the strength of 9° Beaumé) at a temperature of 15° C. Etch galvanically in this bath by placing in it a clean |104| copper dish. The plate prepared for etching as per page 84, is rubbed bright at the four corners and four S-shaped narrow strips of sheet copper are so fastened to the bright zinc that the S-shaped end rises about three millimetres over the picture. Then place the plate face downward for three minutes into the bath, above the copper plate, which is electrically connected with the zinc by brass strips, so that instantly a strong galvanic current is set up. The etchings are found to be very satisfactory and interesting. In three periods (nine minutes) a beautiful preliminary etching is obtained with rather perpendicular faces.

I cannot recommend etching by shaking, as the sediment causes rupture of the finest lines.

PROCESS FOR HIGH ETCHING IN RELIEF.

Experienced etchers can also apply their art to the reproduction of drawings by means of the printer’s press, in the following manner:

A plate, ready for etching and free from grease, is cleaned with weakly acidified water, the remaining water drawn off with a blotter, and the plate gently heated. By means of a pad a fine paste of graphite is rubbed upon the surface; it is then moderately heated and a very thin gauze-like layer of warm white wax is applied to the graphite surface. After cooling the plate, spread upon it a coat consisting of the finest orange-colored chrome yellow (rubbed to a fine dough with water and gum). In this ground layer we can erase as for deep etching.

Brush the finished surface with writing ink dissolved in benzine (using a fine wide brush). The plate should be warm. Take a pad made of cotton, dip it into water and work over the surface in small circles until the image has become well developed. From this point we can continue according to the usual method.

J. O. MÖRCH.

THE RUNNING OF A WORKSHOP.

The great competition demands of every chemigraphical business a ready, productive organization, which is also attentive to the rules of economy. In following out the latter it is advisable to aim at a division of labor. By giving to the single workmen more practice in each particular manipulation, the quality of the work is also promoted. To secure a lucrative trade, we need the following helpers: 1. A foreman thoroughly acquainted with the whole process. 2. A photographic assistant, who is skilled especially in straight line |105| reproduction, and who aids in the copying of negatives. 3. A carpenter, at the same time polisher of the zinc and finisher of the plates, who will also assist at other things in general. 4. A first manipulator, who understands blacking of the plates and the examination of the same throughout the whole process. 5. A man to form the etching varnish on the plates. 6. A man to scrape off. 7. A man to etch. 8. One to wash plates and to make himself generally useful. With the aid of such a staff it is possible to produce 2000 square centimetres of etching daily, and by the addition of a ninth assistant the capacity can be raised to 3000 square centimetres.

A first manipulator can be trained in three months, a carpenter in the same time, and the others in four to six weeks.

The head of the establishment will, of course, be doubly busy during these first months. Upon his abilities depends the success of the whole.

I think it is inadvisable to introduce etching into all the printing establishments, as production on a small scale is far more expensive and less satisfactory. But it _is_ advisable to add to the chemigraphy a small lithographical laboratory.—J. O. MORCH.

SOME WRINKLES AND DODGES.

As I had to stumble through to success like many others, I gladly give a few little items of practice which may speed the work of others. I like this for a sensitizing solution:

Bichromate of Potash in powder 1 ounce. Water 15 ounces. Alcohol (950) 4 ounces. Liquor Ammonia 1 ounce.

After I have sensitized the gelatine transfer paper I increase the surface quality by laying it upon a glass plate which has been heated _very slightly indeed_ with vaseline. I use a squeegee to secure close contact and then stand it up to dry, say over night. A slight start at one corner with a knife point will cause the paper to leave the glass readily.

It pays always to get the best material. Nothing is worse than a bad quality of zinc. I use No. 10. A strong, well-made clotheswringer will answer for a time, for making transfers, when a lithographic press is not convenient. The pressure should be uniform.

Learn to be systematic until you are familiar with all the details of the work. It might be well for you to make a numbered list of the necessary operations |106| and paste it up where you can see it and refer to it handily. Accustom yourself to having a place for everything and everything in its place. I have seen many an etching lost by disregard of this rule.—C. W. ROCHE.

CARBON PRINTING.

In Chapters III. and IV. on engraving on copper, the resist and relief are made by what is called in photographic nomenclature the carbon process—that is, printing in gelatine to which has been added a suitable pigment. This pigmented gelatine, spread upon paper and dried, is known in commerce as carbon tissue, and is sold of various colors and degrees of density as regards the quantity of pigment incorporated with the gelatine. For our purpose that tissue containing the minimum quantity of pigment is the best (this only applies to the resist or relief on the copper, not to the transparency necessary for printing the resist from; in this case what is known as transparency tissue must be used, and that is made with the maximum quantity of pigment (India ink) incorporated with the gelatine), but as the subject of making transparencies in carbon has already been treated of, the present notes will be confined entirely to developing carbon prints upon copper for resists (Chapter III. for reliefs Chapter IV.).

The carbon tissue of commerce is not sold in a sensitive condition; therefore, the first care will be to render it sensitive to the action of light, which is done by immersion in a solution of bichromates of potash and ammonia.

First of all dissolve in eighty ounces of water one and a half ounces of bichromate of ammonia, and one ounce of bichromate of potassium, and filter. Then cut the carbon tissue into suitable sized pieces—_i. e._, pieces a little larger than the subject on the transparency or negative to be used, and a little smaller than the copper plate upon which it is intended to develop the carbon print; next select a sufficient number of glass plates quite free from scratches a little larger than the pieces of tissue, now clean these glass plates carefully by polishing with clean linen or silk cloth free from lint, then dust over with French chalk and again well polish; then coat with thin plain collodion, and when the film is well set place the collodionized plate in clean cold water until the greasy appearance that shows on the first immersion in the water has disappeared.

Place the filtered bichromate solution in a clean dish, then immerse the pieces of tissue, one at a time, taking care that no air bells are allowed to |107| remain upon the surface; if any form, remove them by bursting them with the fingers. After the tissue has been in the solution for three minutes, take one of the collodionized and washed plates from the water and remove one of the pieces of tissue from the bichromate bath, place the two face to face, lowering the tissue gently down upon the collodion film, then place the glass plate upon a bench, lay a piece of Macintosh cloth (larger than the plate) over the tissue, and with a squeegee gently scrape along the Macintosh; this will bring the carbon tissue into contact with the collodion film, and also expel superfluous bichromate solution, but care must be taken not to remove too much of the bichromate else the tissue will be insensitive and print hard. The plate is now placed upon a rack, and all the remaining pieces being done in the same way are also placed upon the rack.

The tissue being thus squeegeed into optical contact (the squeegee is made with a strip of soft rubber fixed between two pieces of wood) with the collodionized glass, it must be dried in the dark room in a current of warm air, not higher than 60° F., else the pigmented gelatine will melt and be useless (bye the bye, the bichromate solution in hot weather should be iced so as to keep the temperature below 50° F.).

When the tissue is dry it is stripped from the glass and stored in a tin tube, and care must be taken to keep it away from the light, as if the tissue be once exposed to the light even for a short time, the action will go on in the dark.

In treating of the transparencies, it is mentioned that the subject on the transparency or negative is marked, this being necessary to form what is called a safe edge to the carbon print. If such a safe edge be not provided, the carbon print will not adhere to the copper during development; therefore, the extreme edges of the tissue must be guarded from the light during the exposure in the printing frame.

The exposure to light under the negative or transparency must be timed by means of an actinometer, which may be improvised by dividing a strip of tracing paper into ten spaces, and numbering these spaces so:

─────┬─────┬─────┬─────┬─────┬─────┬─────┬─────┬─────┬────── │ │ │ │ │ │ │ │ │ 1 │ 2 │ 3 │ 4 │ 5 │ 6 │ 7 │ 8 │ 9 │ 10 │ │ │ │ │ │ │ │ │ ─────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┴──────

Write the figures with good black ink and then cut other pieces of white tracing paper into strips of the same width. |108|

Now lay the piece of tracing paper with the numbers on it, upon a piece of glass 4-1/4 × 3-1/4 inches, and fix it in the centre, then place thicknesses of tracing paper over this so that space 2 has three thicknesses of tracing paper, space 3 five thicknesses, space 4 seven thicknesses, space 5 eight, space 6 nine, and so on up to 10. Now if a piece of ordinary sensitive albumen paper is put into a frame behind this screen, it will form an actinometer, and when, after exposure to light the figure 5 is just visible, five tints are registered.

This actinometer will with practice enable the operator to judge when the carbon tissue has been exposed sufficiently long; the only guide that can be given, is to err on the side of overexposure rather than underexpose.

The carbon tissue being exposed, it is removed from the frame, and placed in clean cold water; then as soon as it begins to uncurl itself, the copper plate is placed in the water, and the two are brought into contact, the tissue adjusted in position upon the copper, then removed from the water, and a squeegee applied vigorously to the back of the tissue, applying the squeegee first one way and then the other.

Now allow to stand a few minutes, then immerse it in water at a temperature of 90° or 95° F., and in a few minutes the pigmented gelatine will begin to ooze from under the paper backing, which may now be stripped off and thrown away. The copper plate may now be raised and gently laved with the hot water, or it may be allowed to remain until the whole of the soluble gelatine is dissolved away, leaving the picture upon the copper plate, which is rinsed in cold water and dried.

For the purpose of copper plate work, the image must be thoroughly well exposed, every detail being impressed, else it will be impossible to get a good photogravure; therefore, until the operator thoroughly understands the use of the actinometer it will be as well to make a few prints upon a piece of opal glass.

Carbon tissue does not keep in a sensitive condition more than a month, under the most favorable conditions, the general time perhaps being a week. The first sign of deterioration is generally shown when trying to mount upon the copper, after soaking in cold water, the tissue refusing to adhere after the application of the squeegee. The best way to test the sensitive tissue is to take a small piece and immerse it in cold water for a minute, then put it into water at 95°, and, if the coating dissolves off the paper the tissue is all right; if it does not, it is useless. Tissue will generally be found at its best about |109| three days after sensitizing, and will gain rapidly in sensitiveness daily afterward.

Carbon tissue can be made at home, the following being the formula:

Gelatine (soft) 10 ounces. Sugar 4 ounces. Water 30 ounces.

Dissolve the gelatine at as low a temperature as possible, then add the sugar and churn thoroughly; then add sixty grains of India-ink, previously dissolved in a little water, again churn, then strain through muslin into a dish (which dish is placed in another containing hot water). Now take two sheets of paper, grasp one end tightly and drag them rapidly through the tissue compound, and directly they are lifted clear of the solution let an assistant grasp the bottom and you dropping the top, will reverse the sheets and keep the gelatine on the surface of the paper; when the gelatine has set, divide the two sheets and hang up to dry; when dry the subsequent proceedings are the same as for commercial tissue.

COLAS’S BLACK PROCESS.

This process will often be found useful to reproduce a drawing on yellow tracing-paper, so as to give a more suitable copy to photograph from.

Coat with a fine sponge a hard, well-sized paper, with

Water 300 parts. Gelatine 10 parts. Perchloride of Iron (dry) 20 parts. Tartaric Acid 10 parts. Persulphate of Zinc 10 parts.

and dry in a dark-room.

When dry, expose under the tracing until the greenish-yellow tint of the paper has disappeared, except where covered by the opaque lines.

Development is effected in a bath made by dissolving 20 parts of gallic acid in 200 parts of alcohol and 1000 parts of water; then wash in plenty of clean water.

MORDANTS FOR ETCHING.

I. MORDANTS FOR STEEL.—Nitric acid forms the basis of most fluids for etching steel as well as for other metals. Acetic acid and alcohol are sometimes added, and some formulæ contain nitrate of silver, corrosive sublimate, salts of |110| copper, etc. Iodine is also a most efficient mordant for steel, and Mr. Fox-Talbot used the chlorides of iron and platinum for etching his plates through the coating of bichromated gelatine.

_Plain Acid Mordant.—(Kruger.)_

First biting: Muriatic or Nitric Acid 1 part. Water 8 parts.

Stronger: Acid 1 part. Water 4 parts.

Deepest: Equal parts acid and water.

_Kruger._—Chromic acid, diluted according to the effect to be produced. This also serves for zinc, copper, and brass, and bites with great ease and certainty, making a good vertical cut.

_Ed. Turrell._

Glacial Acetic Acid 4 parts. Absolute Alcohol 1 part. Nitric Acid (specific gravity, 1.28) 1 part.

The acetic acid and alcohol are mixed and allowed to stand for half an hour, then the nitric acid is added very gradually. This mordant is applied from one to fifteen minutes, according to the strength desired, and may be strengthened by adding nitric acid.

_Etching Solution with Alcohol._

Alcohol seems to be added with the object of softening the action in the first biting, and of making the mordant bite at once. For etching Niepce de St. Victor’s asphaltum plates, M. Lemaitre used, for the first biting:

Nitric acid, at 36° 1 part. Distilled Water 8 parts. Alcohol, at 36° 2 parts.

And finished off with nitric acid and water, without alcohol.

_Etching Solution with Nitrate of Silver._

Alcohol 6 parts. Distilled Water 9 parts. Pure Nitric Acid 16.6 parts. Nitrate of Silver 0.83 parts. |111|

The liquid improves by keeping. Before beginning, wash the plate for a few seconds with dilute nitric acid (at four per cent.), then apply the above mordant for about three minutes, and wash off with distilled water containing six per cent. of alcohol. Repeat the biting as often as may be necessary, well washing between each operation.

_Deleschamps.—Glyphogen._

Acetate of Silver 8 parts. Rectified Spirits 500 parts. Distilled Water 500 parts. Pure Nitric Acid 260 parts. Nitric Ether 64 parts. Oxalic Acid 4 parts.

This is recommended as being free from the defects of many of the other mordants, and as giving a clean vertical bite.

Several formulæ contain salts of copper.

_Roret._

Nitric Acid 62 parts. Distilled Water 125 parts. Alcohol 187 parts. Nitrate of Copper 8 parts.

Iodine is recommended as a very efficient mordant for steel, being free from the inconveniences caused by the disengagement of gas, as when biting with nitric acid. Messrs. Schwarz and Boehme give the following:

Iodine 2 parts. Iodide of Potassium 5 parts. Water 40 parts.

This may be further diluted up to 40 parts more water, for etching the finest lines. It gives good deep lines, sharp, and with clear edges even, for the finest and closely ruled lines have no tendency to run one into the other.

The following resembles the etching fluids for copper, commonly known as “Dutch mordant.”

_Cooley._

Hydrochloric Acid 5 parts. Water 95 parts.

Mix and add:

Chlorate of Potash 1 part. Water 50 parts. |112|

_Cooley._—For electric etching with the battery, a solution of common salt is used.

II. MORDANTS FOR COPPER.—The most useful mordants for copper are nitric and nitrous acids, more or less diluted with water. Latterly, however, a mixture of chlorate of potash and hydrochloric acid, known as the “Dutch mordant,” has come more into use. For some purposes, perchloride of iron in solution is a useful mordant, particularly in photographic work with gelatine films. These two latter mordants bite more quietly than the acids, so that the lines are not so much enlarged, and there is not the same risk of close lines running together and other inconveniences caused by the evolution of bubbles of gas.

_Acid Mordants.—(Lalanne.)_

Nitric Acid, at 40° 1 part. Water 1 part.

With a little old etching solution added, or pieces of scrap copper.

_Malaret._

Nitric or Sulphuric Acid 1 part. Saturated Solution of Bichromate of Potash 2 parts. Water 5 parts.

Fizeau used for daguerrotype etching a mordant composed of nitric, nitrous, and hydrochloric acids.

_Dutch Mordant._

Fuming Muriatic Acid (specific gravity, 1.190) 10 parts. Water 70 parts.

To this add a boiling solution of

Chlorate of Potash 2 parts. Water 20 parts.

This may be diluted with from 100 to 400 parts of water as required.

Perchloride of iron, more or less diluted in water, is, according to Hamerton, an excellent mordant. It bites deep and clear, without enlarging the line much, and there is no ebullition, as with nitric acid. It is particularly useful in photographic etching through gelatine, as the latter is insoluble in it.

In most cases the mordant is flowed over the plate, or kept moving on it in the same way as a photographic developer. Such mordants are generally used for finishing off and deepening the light tints, and are called _eau fortis à couler or à passer_. The following formulæ are given: |113|

_Roret.—(Abraham Rosse’s.)_

Strong White or Distilled Vinegar 3 litres. Sal Ammoniac 180 grammes. Common Salt 180 grammes. Pure Verdigris 120 grammes.

A little oxalic acid is sometimes added. The solids are ground up, and boiled in the vinegar. Acetic acid at 3°, or pyroligneous acid, may be used in place of vinegar, and, if too strong, more vinegar should be added.

The following, used by Callot and Piranesi, is similar and prepared in the same way:

Strong Vinegar 8 parts. Verdigris 4 parts. Sal Ammoniac 4 parts. Salt 4 parts. Alum 1 part. Water 16 parts.

For relief etching use only 10 parts of water.

_Relief Etching._

For etching copper in relief, the following glyphogen is recommended by Deleschamps:

Nitrous Acid, at 30° 2 ounces. Acetate of Silver 6 drachms. Hydrated Nitric Ether 16 ounces.

The nitric ether is prepared by mixing two ounces each of nitric acid and alcohol, and, when the reaction commences, stopping it by adding eight ounces of distilled water.

_Tint Etching._

Flour of sulphur mixed with oil forms a good composition for etching tints. It can be applied with a brush. For a flat tint, Hamerton says “Oil the plate liberally with olive oil, and blow flour of sulphur upon this.” The sulphur, if allowed to remain on the plate, will produce a flat tint, more or less deep in proportion to the time it remains.

Roret gives the following formula for tint etching:

Bay Salt 2 parts. Sal Ammoniac 1 parts. Verdigris 1 part.

These are pounded together, and the mixture kept in a bottle. |114|

When required for use, grind up a little in a glass with some syrup of old honey, so as to make a mixture which flows readily. It may be used with a brush like a color. It is used after the bitings of aquatint plates with acid, to give finish and vary the tints.

_Fielding (for aquatint)._

Nitrous Acid 1 part. Water 5 parts.

For the strongest touches, nitrous acid and water, equal parts, applied with a feather or brush. No. 19 may also be used for this purpose, either with or without a little gum.

_Hamman._—Dilute nitric acid at 12° (sp. gr. 1.09), mixed with:

Distilled Water 12 parts. Alcohol 3 parts.

This is said to give a grain in biting, so that the ordinary grained ground may be dispensed with.

_Electric Etching._

It has frequently been proposed to etch by means of electricity, and in some cases it may be an advantage to do so.

The copper plate to be engraved is attached to the positive pole of a suitable battery and placed as anode in a solution of sulphate of copper, or in water acidulated with sulphuric acid.

In suitable cases, different degrees of depth may be given, putting parts of the anode and cathode nearer together or further apart.

Grove etched daguerrotype plates with a single pair of Grove or Bunsen cells, by inserting the plate to be etched, and a platinum plate of the same size, in a wooden frame having two grooves a quarter of an inch apart.

The daguerrotype having been attached to the battery as anode, and the platinum plates as cathode, the frame is immersed in a suitable vessel filled with

Hydrochloric Acid 2 parts. Distilled Water 1 part.

Contact is made for about half a minute, after which the plate is removed from the acid, washed thoroughly with distilled water, then placed in a solution of hyposulphite of soda or ammonia, and the deposit removed from the surface |115| with gentle rubbing with cotton. It is again rinsed with distilled water and dried.

MORDANTS FOR ZINC.

The comparative cheapness of zinc would give it an advantage over copper or steel for engraving or etching with the graver or point, but it does not seem to be recommended for these purposes. It is hard to cut with the graver, and, though it bites easily, it is not suitable for fine work. Another defect is that it will not stand a long impression; but this may be overcome by surfacing the plate with copper. The principal uses of this metal for printing purposes are for surface printing or zincography in the same manner as lithography, and for the process of biting in relief, and zinco-typography or Gillotage, now so largely employed as a substitute for wood blocks. It can also be engraved very delicately in the same style as engraving is done on stone, through a coating of gum.

The etching fluids for zinc are of two entirely different kinds: first, mixtures of gum and weak acids used for preparing plates for zincographic printing in the lithographic press, or for preliminary inking preparatory to being bitten in relief by the Gillotage process; and secondly, mineral acid, more or less dilute, used for biting in relief and ordinary etching.

_Zincographic Etching._

This kind of etching is more of a preparation of the plate for printing than engraving or biting, the object being merely to fill up the pores of the metal with gum, and prevent it receiving printers’ ink from the roller elsewhere than on the lines of the drawing.

The solution most commonly employed for this purpose is a mixture of gum and decoction of nut-galls, in use at the Ordnance Survey Office, Southampton, and given by Sir Henry James in his work on _Photo-zincography_. It is prepared as follows: Four ounces of Aleppo galls are bruised and steeped in three quarts of cold water for twenty-four hours; the water and galls are then boiled up together, and the decoction strained. The gum-water should be about the consistency of cream. One quart of the decoction of galls is added to three quarts of the gum-water and to the mixture are added about three ounces of phosphoric acid, which is prepared by placing sticks of phosphorus in a loosely corked bottle of water, so that the ends of the sticks may be uncovered. The oxidation of the phosphorus produces phosphoric acid, which dissolves as fast as it is formed. |116|

The etching solution should only just mark a piece of plain zinc.

In Richmond’s _Grammar of Lithography_ the following modifications of this formula are given:

Decoction of Nutgalls 3/4 pint. Gum Water as thick as Cream 1/4 pint. Phosphoric Acid Solution 3 drachms.

Boil one and a quarter ounces of bruised nutgalls in one and a quarter pounds of water till reduced to one-third, strain, and add two drachms of nitric acid and four drops of acetic acid.

Richmond recommends, however, the use of a simple decoction of galls without acid, and gumming in after etching.

Scamoni has the following, by Garnier: Boil about one and a half ounces of bruised gall-nuts in a pint of water till reduced to one-third, filter, and add two drops of nitric acid, and three or four drops of muriatic acid. For very fine work this may be weakened with water. It is applied for about a minute, then washed off, and the plate gummed.

_Zinco-typographic Etching._

In biting zinc plates in relief, the acid generally used is nitric of different degrees of strength, according to the nature and state of the work.

After the transfer is made, the plate is etched with one of the foregoing preparations, then inked in and dusted with finely powdered resin, which adheres only to the lines. This procedure is followed after every biting, the plate being warmed to melt the resin and inky coating, so that it may run down between the lines and protect them from the undercutting action of the acid.

Kruger, in his _Die Zinkogravure_, recommends for the first relief etching, nitric acid 30 to 40 drops to 100 grammes of water, applied for five minutes. For each subsequent etching, 8 to 10 drops of acid are added for each 100 grammes of water, and the time is increased, from five to fifteen minutes. For the final etching of the broad lights he uses:

Muriatic Acid 4 parts. Nitric acid 1 part. Water 16 parts.

To soften down the ridges between the lines the plate is inked and dusted as before, and etched with dilute nitric acid at five per cent., applied for a |117| minute, and the inking, dusting, and etching repeated as often as may be necessary.

THE DIFFERENCE.

Finally, in this department, only the novice will require an explanation of the varied productions possible by means of the processes already given. As actual examples, reference may be had to the illustrations in this work. Figures 1, 2, and 3 are specimens of line work, zinc etchings made from pen and ink drawings. The figures in the following chapter were made in the same way.

Figures 4, 5, 6, and 7, as well as some others, are zinc etchings reproduced from Mr. Mörch’s work. With them more effort has been made to secure half-tone by a variety and quantity, or filling, in of lines. The example below was made by using the objects (ferns) themselves as the negative, without any interposition from photography, and shows one of the possible applications of zinc etching. It is delicate work and is very beautiful when carefully done. An example of true half-tone, obtained in the manner described in Part II., is the one which follows. It was made by Mr. F. E. Ives, the earliest inventor of a half-tone process, several years ago. The larger examples of half-tone work which appear in this book are made after the most modern fashion and formulæ, as described in Part II., and will serve well to show what the worker in this fascinating process may expect to reach after patient and persistent experiment. When we look upon Fig. 1 and see the very best that zinc |118| etching could do a few years ago, and compare it with the Mosstype and other half-tone pictures now possible, we may well wonder at the growth of the art.

It has been attained by the careful and persistent plodding of a few. Many a method has been discarded for a newcomer, and there is no telling what may come next. Photography has about revolutionized the illustration of books and magazines, and has made the newspaper far more attractive than it was a few years ago. It has made the faces of almost every renowned individual familiar in every land and in every household, and the attractions of every known country have been so pictured by it that every intelligent child is familiar with them. It has been said that process-engraving has supplanted wood-engraving. This is not so. How many newspapers were illustrated before process-engraving was made available? How many works of the old masters and gems of the old museums abroad were made familiar to the lovers of pictures everywhere, by wood-engraving? Instead of coming into the arts to take the place of another, photo-engraving has made a place for itself and a market for itself. Moreover, it is refining and educating the masses by creating a love for art, where before its advent, there was very little feeling for the beautiful. Its accomplishments have been marvellous, and yet they have hardly begun. The good photography has done in bringing the wood-engraver up to his duty in following the artist in every line and light and shade, it will augment by teaching him how to secure the loveliest effects of nature. It will make way for more wood-engraving as well as for more process-pictures if you choose to call them such.

|119|