This process is for making photographic reproductions of a subject in black lines on a white ground, half-tones and shadings being indicated by hatching, or stipple, but no washes of color are permissible. The object sought for from such a subject is to produce a transfer which can be laid down upon stone or zinc, and proofs printed therefrom in the ordinary lithographic press or machine.

To gain this end there are three methods: the first, by printing upon paper prepared with bichromated gelatine, the lines of which, after exposure to light under a direct negative (i.e., a negative taken without a mirror behind the lens), will retain ink, whilst the gelatine protected from light absorbs water, and rejects the ink. The result is a replica of the original in fatty ink, and may be transferred to stone or zinc, and printed from by the usual lithographic method.

In the second method, a print is made upon zinc from a reversed negative (in the same manner as directed in Chapter V., Part I.) in bichromated albumen, which is rolled up in transfer ink, and from that a transfer is pulled on Scotch transfer paper, which may then be transferred to stone or zinc, and printed from at a litho. press or machine.

In the third, and by far the best method, the print is made from a reversed negative on zinc, in bitumen, as directed in Chapter V., Part I., then rolled up in transfer ink, the transfer pulled on Scotch transfer paper, then transferred to stone or zinc, and printed from at a litho. press or machine.

The defects inherent to the first method are, first of all, in the preparation of the gelatine paper; this is tedious and messy. Then there is always danger of breaking the lines in transferring, and also the difficulty of working exactly to scale. {130}

The second method is quick, easy, and simple, the only drawback being a tendency of the lines to thicken. With this and the third method there is no difficulty in getting absolute scale.

The third method is perfect, and presents no drawbacks.

The two latter methods having been amply explained in Part I., it will not be necessary to redescribe them, except to explain that when the print is made on the zinc in albumen, it is gummed in, fanned dry, then damped off with a wet sponge, followed by a damp cloth, rolled up with transfer ink, and the transfer pulled upon good Scotch transfer paper.

The same remarks apply to bitumen prints.

For a transfer printed in bitumen, the image is developed in turpentine, and when this is completed, wash the plate thoroughly under the tap, then immerse it in the graining bath (Part I., Chapter I., page 24), and keep the tray rocking for a few minutes; the effect of this will be to destroy the polished surface of the metal, substituting a pearly matt surface, which will show up the picture properly, and allow the operator to judge whether any of the fine details are wanting; if there are, it will be necessary, if the details are dissolved out, to repolish the zinc, first with pumice-stone, then with snake-stone, then with pumice powder, finishing with fine rouge; then coat with bitumen, whirl, and again expose to light, giving this time, longer exposure under the negative.

But if the fine details are buried in undissolved bitumen, a further immersion in the turpentine bath will soon clear them; then again wash under the tap, immerse in the graining bath, again wash, then, with a sheet of clean blotting paper, remove the surplus water, and allow the surface to dry in a cold current; but beware of using heat, as it has a tendency to make the bitumen image refuse ink in rolling up.

The zinc being dry, it is gummed in, fanned dry, then the gum is washed off, and the image rolled up with a leather roller charged with transfer ink. As soon as the bitumen has taken the transfer ink all over, a transfer is pulled upon Scotch transfer paper, which in turn is transferred to stone for printing from.

In rolling up these prints upon zinc, care must be taken to keep the surface (whether the image is in albumen or bitumen) properly damp.

The preparation of paper transfers will be treated upon in the next chapter.

The negative from which these transfers are made, must have all the characteristics of a good negative for printing on zinc for etched blocks, viz., the lines {131} must be represented by clear glass, and those portions of the negative representing the whites of the original, must be as near opaque as possible.

The subjects to which photo-lithography is applicable, are those that are strictly in line, or stipple, or dots, or cross hatched, or chalk drawings; in fact, any subject that may be done by lithography, or in black and white; but no shading by color washes is permissible.

Transferring to stone or zinc is done as follows:

First of all, the transfer is trimmed to proper size; it is then placed in a damping book, made by placing wet sheets of brown or good printing paper alternately with dry sheets, then placing all under a weight for a few hours, until the whole of the book is evenly damp; the trimmed transfer is allowed to remain here until limp; it is then sponged on the back with a very little of oxalic acid (half an ounce), water eighty ounces; now lay the transfer carefully down on a perfectly clean and polished stone, backing the transfer with a piece of smooth paper. Having adjusted the pressure of the scraper on the stone, pull through twice, then reverse the stone in the press, and pull through twice more. Then remove the backing and lift the transfer from the stone, when the whole of the ink should be upon the stone, leaving the paper quite clean. Now, if the picture is quite satisfactory, wipe the stone first with a wet sponge, then with a damp cloth, then gum in and allow to dry, and, if possible, to stand with the gum on all night.

Paper for photo-lithographic transfers may be made by coating bank post paper or a good hand-made writing paper, with

Put the above into a wide-mouthed bottle or jar, and allow the gelatine to soak until soft; then place the vessel in a large saucepan containing cold water, and set on a fire, or over a gas-burner, and by the time the water in the saucepan is hot the gelatine will be dissolved. Then add slowly (stirring the gelatine with a glass rod) one drachm of a ten-grain solution of chrome alum. Now strain the gelatine solution through fine muslin into a clean dish, standing it in a larger dish containing hot water; float the bank post paper upon this solution (taking care to avoid air-bubbles) for two minutes, then lift it off slowly and hang it up to dry, pinning it by two corners to the edge of a shelf.

When dry, the operation is repeated, but this time the paper is hung up to dry by the two opposite corners, so as to equalize the coat of gelatine.

When dry a second time, it must be floated for two minutes upon

(Shake up well, and filter into a cold dish.)

Paper prepared as above will keep for any reasonable length of time.

For use, it is drawn slowly through a solution composed of

This being done, the paper is again hung up to dry, this time in a dark room.

When dry, the paper should be laid face down, upon a polished litho. stone, and be pulled through the press three or four times, so as to get the surface as smooth as possible, and insure absolute contact. {133}

This must be done in a yellow light, or in a room lighted by gas or oil light.

The paper is now placed in contact with the negative, in a printing-frame, and exposed to light; the exposure for such paper should be from five to fifteen minutes.

Note well that these paper transfers are printed from negatives taken direct in the camera, without the intervention of the mirror, therefore negatives suitable for printing paper transfers will not do for printing upon zinc, or vice versa.

The progress may be watched by undoing one side of the back of the frame, and examining the image in the dark room; but in damp weather this should not be done too often, as the paper may expand or contract, and blur the image.

The exposure to light under the negative being complete, the print is removed from the frame in the dark room, and is next coated with a thin film of ink as follows:

A smooth litho. stone is carefully coated with a fatty ink by means of a leather roller, extreme care being necessary to insure an even coat of ink over the stone; this being attained, the exposed print is laid face down (the room being lit by yellow light or gaslight) upon the inked stone, then a piece of backing paper laid upon it, and pulled through the press, with a good nip upon it; pull it through twice, then reverse the stone on the press, and again pull through twice, which will leave a fine, thin film of ink upon it. Now take the inked print, and place it in a tray of clean, cold water, allow it to remain therein for five minutes, then lay the print upon a piece of glass, and rub it gently with a pad of cotton-wool—previously wetted in the water. This will remove the ink from those portions of the paper that were protected from the action of light by the opaque portions of the negative, representing the whites of the original.

The application of the pad of cotton-wool is continued until the whole of the picture is cleared from superfluous ink, and the lines composing the image are evenly coated with ink. The ink adheres only to those portions of the paper which the light has acted upon, through the negative.

Now wash the transfer under the tap, then hang it up to dry. When dry it is ready for transferring to stone or zinc.

To transfer to stone or zinc, place the transfer first of all in the damping book, and when limp place it upon a clean, cold, polished stone, and pull it through the press. {134}

When transferred, the image is treated in exactly the same manner as an ordinary transfer on stone or zinc.

The enamelled double transfer paper sold for double transfer carbon work may be used for photo-litho. transfers by floating it upon

and then dried.

Paper thus prepared must be kept in a dry air-tight case, and just before using is laid face down upon a smooth litho. stone, and pulled through the litho. press. After this, it is placed in contact with the negative in the printing frame, and exposed to light until the details are visible. Although the progress of the action of light can be seen, the frame must not be opened too often, or the paper is apt to expand and blur the image. After exposure the print is inked up, developed, and treated exactly as explained above.

The ink suitable for inking up the stone, previous to laying upon it the exposed print, is composed of

Put the ink and fat into a small iron or earthenware pot, and place it over a Bunsen burner, or a paraffine stove, or on the hot plate of a kitchen stove (but not over an open fire); allow the heat to melt the two ingredients, stir so as to incorporate them thoroughly; take great care not to allow it to catch fire; if it does, at once extinguish the flame, as the firing would be apt to spoil the ink. When thoroughly melted and incorporated, pour into a tin, or pot, for use when cool; the time occupied in making this ink will not exceed twenty minutes. The mutton fat is obtained by dropping solid kidney suet (shredded) into a pan of clean boiling water, then allowing to cool, when the fat is taken off the surface of the water, freed from damp and stored for use.

Another formula for the preparation of paper, to be inked up, after printing in the same manner as the above transfers, is to coat paper twice with the following preparation, drying between each coat: arrowroot, 1 ounce; wet this thoroughly with 5 ounces of cold water, stirring well with a spatula, adding more cold water, if necessary, to moisten the lot; then pour over it 20 ounces of boiling water, stirring all the time; if, when the 20 ounces are added, {135} the arrowroot has not thickened, add more boiling water until it does do so; now add ¹?/?₂ an ounce of powdered bichromate of potash and stir until dissolved; then strain through muslin into a warm dish and float the paper upon it whilst hot, and dry at a temperature of 70°F.

If the bichromate of potash be omitted, the paper may be prepared in quantity and stored away for future use, being made sensitive by floating for five minutes upon

Paper for either gelatine or arrowroot transfers, after keeping so long after preparation as to be useless, should not be thrown away, but should be again floated upon bichromated gelatine or arrowroot, and after drying will give finer results than new paper.

Prof. Husnik’s photo lithographic transfer paper is obtainable in England and in America. He recommends the following chromate bath:

Keep well corked in a dark place.

Prepare a solution of

Soak the gelatine in the water (cold) until quite soft, then melt it by the application of heat (nothing is better for this sort of work than a Bain Marie, a domestic utensil with a porcelain pan enclosed in one of tin); then add the sugar and stir well, continuing the application of heat until a temperature of 150°F. has been reached; now strain the gelatine through muslin, into a clean dish placed in a larger dish containing boiling water, the heat from which will keep the solution of gelatine in a properly liquid state during the operation of coating the paper.

The best for these transfers is a good hand-made writing paper, or good bank-post.

Cut the paper into suitable sizes, leaving a little extra margin at one end, and float it upon the hot gelatine solution as above; be careful in laying the paper upon the gelatine, that air bells are avoided; when the sheet is laid upon the surface, raise it rapidly, and throw it at once over a cylinder of cardboard or of wood, and at once commence to revolve this cylinder rapidly, first in one direction, and as the limit of the length of paper is reached, revolve it in the other, which motion will alternately bring first one end uppermost and then the other. By this means an even coating of gelatine upon the paper is secured, which is not possible when the paper is hung up by clips directly it is taken from the surface of the hot gelatine. The cylinder is kept revolving until the gelatine has set, when it may be hung up to dry upon clips, or laid face up, over a line upon a piece of cardboard; during the operation of revolving the cylinder, any air bells formed in the gelatine coating may be removed by blowing or pricking them.

This, to my mind, is a most elegant method of coating small sheets (up to thirty inches long) with a coat of gelatine, for which I willingly give the {137} Royal Engineers the credit, it having been demonstrated to me by Ex-sergeant Dalton, of that corps.

Paper coated in this manner, when dry, is ready for sensitizing; but if coated in the ordinary manner, it should, when dry, be coated a second time and hung up to dry in the opposite way that it was the first time.

Paper coated with gelatine solution as above, may be stocked, as the coating does not deteriorate with time; but the operator must be careful not to allow the solution of gelatine to get below 125° during coating, else the surface will be sticky. The temperature of the drying room must not exceed 70°, in fact, 60° will be best.

Paper so coated is sensitized by immersion for three minutes in

In hot weather this solution must be kept cool with ice.

When the time of immersion has expired the paper is removed, and laid face down upon a sheet of glass free from scratches—which sheet of glass has been well polished with finely powdered talc (or French chalk)—now squeegee the back of the paper vigorously, to remove the superfluous solution and bring the surface of the paper into absolute contact with the glass plate. The sheet of glass is now placed in a rack, in the dark room, until the paper is quite dry, when it may be readily stripped off the glass, and is ready for printing the transfer. The operation of drying should be done in a current of air at a temperature of about 60°, and the paper must be quite dry before attempting to strip it from the glass.

The exposure under the negative is the same as described in the previous chapter.

When sufficiently exposed, the print is removed from the frame in the dark room, and at once immersed in cold water, where it is allowed to stay for five minutes, when it is withdrawn and laid upon a piece of plate glass, or a zinc plate, the face being uppermost; then the loose end of the paper (provision for which must be made in cutting the paper) is tucked under the plate, so as to hold the transfer in position in the subsequent operations.

Now take a glue roller (the same as used for inking up the albumen image on zinc, described in Part I., Chapter IV.), and having spread a little of the ink described in the last chapter (chalk, litho. ink, and mutton fat) upon the slab, charge the roller carefully with a thin coating of ink, and then, having {138} removed any moisture from the face of the transfer with a soft sponge, apply the inked glue roller, rolling one way only—i.e., from the body (presuming that the edge of paper tucked under the slab is next the body of the operator); continue rolling until the whole of the lines forming the picture are coated with ink, and the whites quite clean and free from ink. If the roller should get wet from water oozing from under the transfer, wipe it with a damp cloth and then roll it a few times on the inking slab, and continue rolling the transfer. Be careful that the portion of the transfer representing the whites of the picture has absorbed its full modicum of water before beginning to roll up, and also that there is not too much ink upon the roller. When the transfer is successfully inked up, it is hung up to dry, and when dry is trimmed to size, placed in a damping book, and transferred to stone.

The exposed transfer, after wetting, and being placed upon the plate of glass, or zinc, may be developed in another way. First remove the superfluous water from the surface with a soft damp sponge, then rub it gently all over with a pad of cotton-wool dipped in a thin mixture of ink thinned with turpentine and well mixed with a palette knife (this ink should be a little thicker than ordinary copying ink); all the image must be covered with the ink. The turpentine is then allowed to evaporate, when by rolling with the glue roller from the body, the ink will clear away from the whites, leaving the lines sharp and distinct. Do not use too much pressure, else the ink may be removed from the lines, in which case cover the whole picture with a fresh coat of the thin ink, and again roll off. The subsequent operations are the same as for the other paper transfers.

The ink for this method is made by melting over a Bunsen burner, or paraffine stove,

When these are melted and well stirred together, set the mixture on fire and allow to burn for three minutes, then extinguish by putting the cover on the pot or pan, then pour it into a tin. When cold it is ready for use.

In handling the sensitized gelatine paper for transfers, every care must be exercised to keep the paper from being exposed to the action of light, before and after exposure in the printing frame, else there will be great difficulty in getting clean transfers.

A good smooth paper is floated for five minutes upon finest picked

This is dried in the dark, then exposed to light in a printing frame under a direct negative. It is then laid, face down, upon a polished zinc or stone, if a line subject, or on a grained zinc or stone, if a half-tone subject; upon the back of the print several sheets of damp paper are laid, and then the whole is subjected to very heavy pressure in a hydraulic press, so that the water in the damp paper may be forced through the print and dissolve the gum in the unexposed parts of the sensitive gum coating (which is still soluble). The dissolved gum attaches itself to the stone, whilst the exposed parts being rendered insoluble by the action of light, the damp has no effect upon it, and the stone is protected in those parts.

When the stone has been under pressure for a sufficient length of time, to allow the small traces of gum in the deepest shadows to attach themselves to the stone, the pressure is removed, the stone withdrawn, and the paper carrying the photographic print is carefully lifted up, leaving the bare negative image on a gummed ground. The stone is well dried, and covered all over with a greasy ink applied by a roller or otherwise. The ink is thus brought into contact with all parts of the stone or zinc unprotected by the gum.

The image is then washed out with turpentine, and the gum removed by a damp sponge, after which the stone or zinc is rolled up in the ordinary manner with a leather roller, and is printed from in the ordinary manner.

Of course, it will not be expected that the best results are obtainable by so simple a process. Perhaps in no other branch of work does an outlay of thought and time “pay” so well as in the practice of these interesting photo-printing methods.

Now the inked and exposed transfer is placed in water at 80°F., and allowed to remain for three or four minutes, when it is taken from the water and placed upon a plate of glass, and the superfluous ink is removed by means of a sponge dipped in the hot water. If the negative has been sufficiently opaque, and the exposure right, the image will quickly develop, the lines retaining the ink, while that upon the whites will come away.

Hot water is used where the coating is of gelatine only; if gum arabic, or albumen has been used, then, after inking up on the stone, the transfer must be developed in cold water, and cotton-wool used to remove the ink from the whites, rubbing very carefully with very little pressure.

Paper prepared with a thick coat of gelatine may be developed in another way; after removing it from the printing-frame, the transfer is inked up on the stone, then placed in a dish of cold water and left there for five or ten minutes; then removed and placed upon a thick glass slab, the end tucked under so that when placed on the bench the slab will press the paper and keep it in position. Now, with a sheet of clean blotting-paper, remove the water from the transfer, using pressure with the hands from the end tucked under the slab; then, with a glue roller, roll from the tucked under end until the image is developed. Instead of inking the transfer up when dry, the transfer may be placed in the cold water directly it is taken from the printing-frame, and allowed to remain for ten or fifteen minutes, during which time the image will swell, by the whites absorbing water. Now place upon the glass slab (one end being tucked under), and remove the superfluous water first with a {141} sponge, then with a damp cloth; now dip a sponge in transfer ink thinned to the consistency of cream by turpentine, and dab all over the damp transfer, then allow it to stand until the turpentine has evaporated. Next take the glue roller and roll the transfer until the whites are clear; only roll one way—i.e., from the end tucked under the slab.

The transfers being developed, they are rinsed with clean water, and hung up to dry in a current of cool air. If dried at too high a temperature, the transfers will be inferior, and difficult to handle.

Instead of using a slab of glass, and tucking the end of the transfer under­neath, a pro­per de­vel­o­ping-board may be used as follows: A is a clamped board 18 inches by 12 inches, by 1 inch thick; B is another 4 inches by 12 inches; these are hinged together at C, the hinges being let into the boards un­der­neath. Now, if the trans­fer be laid upon the board A, the end placed in the aper­ture C, then the pres­sure of the rol­ler will cause the piece B to clamp the paper quite tight.

A few lit­tle dif­fer­ences in ma­nip­u­la­tion are re­quired by the various trans­fer papers found on sale in the market. For this reason I add the ins­truc­tions given by Prof. Husnik for his transfer paper.

Take a pane of glass, coat it with a fatty substance, as tallow or wax dissolved in benzine; wipe the glass clean, so as to leave only a trace of fat on; lay the paper in the solution about one minute, drain off and then lay the paper face down on the glass, removing all air bubbles by rubbing over the back with a rubber straight edge, or better, a squeegee. When dry, the paper will leave the glass easily and will have a glass-like surface.

The development is the same as above described. This later method gives excellent results.