PHOTO TRANSFER FROM PAPER.

In this method, now universally employed, success may be said to depend more particularly upon two points. (1.) The paper for the transfer. (2.) The suitability of the negative for the purpose in view. The properties and preparation of a suitable transfer paper demand a few words. It should be of substantial body, smooth and well sized; that known as bank post is usually employed in this country. Professor Husnik in his patented process proceeds as follows: 1 part of finest gelatine is swelled, and then dissolved in 24 parts of water a solution of chrome alum 1-100 in water is added, and the solution while still warm is poured into a large zinc dish heated to 34° R. by means of a petroleum or spirit lamp. Remove any scum from the surface of the solution, float the paper one sheet at a time, and suspend to dry. The sheet is floated upon the gelatine solution a second time, and once more suspended, this time by the diagonal corner to that by which it was previously hung. Prepare a solution of white of egg 1 part, water 2 parts, and on this float the paper on one side. After again drying it is ready for sensitising, for which operation prepare a bath of water 14 parts, bichromate of potassium 1 part, methylated spirits 4 parts, adding sufficient ammonia to turn the reddish solution a bright yellow. If the paper is not prepared in large quantities, but only for immediate use, the ordinary gelatine paper of commerce[Q] may be employed with advantage, if further prepared by floating upon a bath of albumen (beaten to a froth and allowed to stand) 50 parts, water 50 parts, bichromate of potassium or ammonium 7 parts (Märkl), upon which bath the paper should be floated for five minutes. This solution is subject to the disadvantage that even in the dark it will not keep for more than a day or two, therefore it must be used at once. All photo-lithographic transfer papers, after sensitising, should be used within a few hours of their preparation or their good qualities are partially sacrificed, the solubility of the albumen layer in cold water being impaired. Photo-lithographic transfer paper prepared as above described has been for some time in the market, and may be procured as an article of commerce, in an unsensitised condition; it will keep indefinitely in this state, and may be sensitised as required. The surface should not be allowed to remain in contact with the bath, neither should the immersion be lengthy, as in either case the surface of the paper would probably suffer. After drying by suspending by one corner in the dark, the chromated paper is exposed under a suitable negative—if possible to the sun—for a few minutes only; it may be examined by non-actinic light, and when the image appears brown or grey upon a yellow ground, and all details are visible, it is removed from the copying frame and entirely covered with a thin coating of transfer ink. This as purchased is much too stiff for use, and must be reduced by means of turpentine to such a consistency that it is possible to distribute an even and quite thin layer upon the surface of the print, without its penetrating to the paper. The ink should be so thin that it presents a grey, not black, appearance.

[Q] For instance, the double transfer paper as used in the carbon process.—Trans.

Those who may find it necessary, or who care to prepare their own ink, should take—chalk ink (printing) 4 parts, beeswax 10 parts, resin 7 parts, turpentine 40 parts, tallow 8 parts, Prussian blue 6 parts, ground and mixed in a paste. The chalk printing ink should be melted by gentle heat, then add the wax and resin in a molten condition, then the tallow, and lastly the Prussian blue and turpentine; on account of the inflammable nature of the latter these operations should not be conducted at an open fire. If, after prolonged keeping, this ink becomes tough, and does not readily leave the transfer paper when transferring to stone, the addition of a few drops of olive oil will restore it to a usable condition. The ink is best applied by means of a fine, dry sponge,[R] with which it should be spread on the transfer as evenly as possible, during which operation the print must be protected from actinic light; on its completion the print is placed aside to allow the turpentine to evaporate. This in a warm room will be about ten to fifteen minutes; the print is then placed in cold water, care being taken to remove any air-bubbles from its surface. After remaining for about half an hour the uppermost layer will have become sufficiently loose to allow of its removal, together with the adherent ink not forming part of the picture, upon the application of slight friction.

[R] A smooth composition roller answers equally well.—Trans.

The Development is readily effected by means of a small, fine wet sponge, or a pad of cotton wool well moistened, which is passed over the print a few times with gentle pressure; it will be found convenient during these operations to place the transfer face upwards upon a sheet of glass.

Judgment may be formed at this stage as to the suitability of the negative, and also as to the correctness or otherwise of the exposure under it of the sensitised paper; if it should have been too short the finest lines will not be firm, but appear broken or “rotten,” as it is technically termed. On the contrary, should the exposure have been too long, the spaces between the lines, which should be quite free from ink, will retain a certain amount, in attempting to remove which the transfer will be damaged.

Washing.—Exposure, inking, and development being satisfactory, the print is thoroughly washed to remove the chrome salt. Dry the transfer by means of repeated applications of blotting-paper, and it is then ready for transferring.

Transferring.—The print should retain a little moisture, but be by no means wet. It should adhere to the warmed stone to prevent any probability of it moving while passing through the press.

Transfer too Adhesive.—Should the gelatine surface, in the judgment of the operator, appear likely to prove too adhesive, it may be further dried before use, or placed for two minutes in a one per cent. solution of tannin, and again dried between blotting-paper.

Preparation of Gelatine Transfer Paper, as used in the Imperial Military Geographical Institute in Vienna, is described as follows in the “Photographic Correspondence”:—A sheet of well-sized paper is soaked in a dish of water, and when thoroughly limp is allowed to drain, and then placed on a horizontal glass plate. All air bubbles and superfluous moisture are removed by blotting-paper and a squeegee, the edges of the paper are turned up to the depth of about 2 cm., and a warm gelatine solution (1 to 30) poured upon the paper. It sets in a few minutes, and the sheets are placed upon wire gauze to dry, this operation usually occupying about two days. A day before using the gelatine paper is sensitised by immersing for three minutes in a cold bath of bichromate of potassium (1 to 15). On removal from the bath it is allowed to drain, and the gelatine side placed upon a glass plate. The back is dried with blotting-paper, and all air bubbles removed. These operations and the subsequent drying must be performed in a non-actinic light. It may occur that after these operations the sheets when dry adhere partially or wholly to the glass plate. To prevent such an occurrence it is well to wax the plate, as in the carbon process, or to apply to the surface a weak solution of ox-gall.[S] When dry the sheets are cut to the required size and printed under the negative. On removal from the printing frame they are placed in cold water until quite limp, removed, placed face upwards upon a glass plate, and surface dried with blotting-paper. Should the gelatine swell too much the sheet is placed for two minutes in a chrome-alum solution (1 to 200) and again blotted. Ordinary transfer ink, thinned with turpentine, is now thoroughly rolled up on the inking slab by means of a leather roller (as previously described in the instructions under Collotype); a fine velvet roller, lightly charged with ink, is then passed over the still moist transfer. Should the latter become dry in places it is again passed through the water bath, and the inking is again proceeded with. If the ink adhere to other parts than the design it is easily removed by the application of a damp sponge or the tip of the finger. The process of transferring to stone is as previously described. The stone itself is prepared in the manner described for the autographic process (see page 135). Damp the back of the transfer with water only, and after passing through the press several times, remove the paper from the stone; if of good quality this may be done without tearing. The transferred impression being still easily obliterated, it is better to let the stone stand for a few hours without gumming; this will allow the ink to dry deeper into it. Coat the whole of the surface with a moderately thick solution of gum, and again allow to dry. In this condition it may remain indefinitely, but under any circumstances it is advisable to allow it to remain a day before etching and printing. The gum solution used should be freshly prepared, as when old it becomes acid and acts as a mild etching medium. Remove the gum with a clean sponge previously to printing, and while the stone is evenly damp with gum solution the picture may be either rolled up with stiff chalk ink, applied by means of a leather roller, or, as preferred by many, rubbed in with a sponge containing thinned transfer ink. When the drawing appears clean and perfect the stone is washed with a wet sponge, coated with gum, placed aside to dry, and allowed to stand for a day. After the removal of the gum proceed as previously described, viz., roll up with stiffish ink, nowhere allowing the stone to become dry, and etch. This operation must be conducted with care and judgment, or there will be a probability of losing the finer lines of the drawing. The best mordant to use is nitric acid, so dilute as to taste no stronger than lemon juice, and which, placed upon the edge of the stone for a few seconds, will show only slight effervescence. To this is added a little gum-water, and it is then evenly and quickly spread over the stone. After being allowed to act a few seconds, the stone is sponged over with clean water, and is then ready for printing from.[T] There are many practical lithographers who prefer to entirely remove the visible image from the stone by means of turpentine before printing. A little gum is left upon the stone, and while the latter is still moist the drawing is removed by means of turpentine upon a piece of rag; the latter must not be too frequently changed, or a too liberal supply of turpentine made use of, or the drawing may be irreparably damaged. Unless the latter be the case the picture will reappear upon applying the roller charged with chalk ink. As may be expected, the first few impressions are seldom so perfect as the later productions. After each impression is removed the stone is at once slightly moistened. For this purpose a soft, clean sponge is suitable, or damping cloth, as supplied by dealers in printing materials. The sponge or cloth should be thoroughly wetted, wrung as dry as possible, and in that condition will possess the necessary dampness. In rolling it should be borne in mind that as in Collotype a stronger grip of the roller handles and heavy pressure with slow rolling will deposit ink upon the drawing—while, on the other hand, light quick rolling of the drawing will tend to remove the ink. To leave the stone without gumming after transferring is a convenient method of rendering the transfer more receptive of the ink. In lithographic as compared with Collotype printing the ink is reduced to a far greater extent with varnish, while both the inking slab and roller are charged far more heavily. The paper may be damp, or a dry, well-sized paper may be used.

[S] A more reliable method of imparting to the surface of the paper a high gloss is to squeegee it down upon a ferrotype plate, the surface of which requires no preparation, and the risk of sticking is nil.—Trans.

[T] For etching extremely delicate transfers a decoction of Aleppo gall with gum is to be recommended. 15 gr. of crushed nut galls are boiled for one hour in half a kilo of water and strained through a cloth. To etch the transfer add a few drops of this solution to a solution of gum of a syrupy consistency; spread over the stone with a soft sponge, and allow to dry.

CHAPTER XIX.

Negatives for Photo-lithography.

AN unconditionally good negative is required for photo-lithography, and those who have not seen one produced for the purpose by an expert should endeavour as a first step to do so, or they will scarcely be likely to devote the attention necessary for producing one of a thoroughly suitable character. Not only must the lines of the copy be represented in the negative by clear glass, and the white ground of the original be represented by opacity, but the utmost sharpness of definition of the finest dots and lines to the very corners of the plate is absolutely necessary to render the negative thoroughly serviceable. To produce such a negative a lens entirely free from distortion, and capable of giving microscopic definition, is, of course, a first necessity.[U]

[U] Lenses of the rectilinear or symmetrical class are best.

The Wet Collodion Process is better adapted than any other for the production of suitable negatives, possessing the necessary density and freedom from fog or veil. The bath must work with the utmost cleanliness, and the collodion should not be used too soon after iodising. The developer works better when not quite fresh, and should contain a sufficiency of acid, and the negative, after fixing, should be subjected to a vigorous intensification.

Professor Husnik thus comments upon negatives for photo-lithography:—

“As in photo-lithography only subjects in black and white line or stipple can be reproduced, to the entire exclusion of half-tone, the negatives should represent the copy by clear lines and opaque spaces. This is seldom the case except in instances where the drawings are specially prepared, and the subjects somewhat bold and coarse. For example, in copying a proof from a fine steel engraving the graduated, grey, hair-lines, appear in the negative somewhat veiled, whereas the intermediate spaces between close shading, and which are somewhat toned in the print, are not developed actually opaque in the negative. On this account the fine hair-lines will take longer to print in the copying-frame than the bolder shadow lines. The latter may develop faultlessly, while the ink may leave the hair-lines. The intermediate spaces between close shading may not be sufficiently opaque in the negative, consequently the print is over-exposed in these portions, and during development remains covered with ink. Such faults must be overcome as far as possible by shading the negative during printing in the usual well-known manner.”

The Colour and condition of the original copy will greatly influence the class of negative it is possible to obtain, and if allowable it will be advisable

To Bleach old engravings or other copies, either yellow from age or stained, by immersing them in eau-de-javelle[V] 10 cc., water 100 cc., wash in water for two hours, and finally in a weak solution of hyposulphite of soda.

[V]Chloride of lime1oz.
Water15oz.
Carbonate of potash2”
Water5”

Mix the two solutions together, boil, and filter before use.

Intensifying.—Having developed a clear, sharp negative, wanting only in density, it must be intensified to the utmost limit—without fogging—first with citric acid, pyrogallic acid, and silver. This solution may be applied either before or after fixing, preferably the former; if this course is adopted, after washing and fixing, and again thoroughly washing, the final intensifying operations may be proceeded with. Opinions vary as to the actual best method to adopt, but preference is usually given to an intensification by a salt of mercury or lead; under any circumstances there must be a good deposit of silver to work upon, or the necessary density cannot be obtained. In fact, a negative too thin, submitted to mercurial combinations, particularly the bichloride, will become more bleached and spotty, and the after application of sulphide of potassium will not again restore it; the deposit will assume a dark brown appearance, but the spots arising from the mercurial salts will still be apparent. The two mercurial salts referred to are—(1) Bichloride of mercury, corrosive sublimate, a well-known and highly-poisonous substance used in solution in water, and (2) iodide of mercury, which, used in intensification, acts more evenly, though with somewhat less energy. This substance, which is of a beautiful red colour, is insoluble in water, but is soluble in sublimate, and also in a solution of iodide of potassium. It is recommended for intensification, and is easily obtained by dropping into a solution of bichloride of mercury—with agitation—a concentrated solution of iodide of potassium until the red precipitate as first formed is again dissolved. This yellow solution may be diluted as required by an addition of ten times its volume of water. If, instead of flowing the solution over the negative, a dipping bath be used, into which the negative is steadily lowered for a few seconds, a more uniform intensification is likely to ensue. Carefully watch the plate, and stop the action before it goes too far, or the silver deposit will lose strength in parts. An important gain in density may be obtained by exposing to sun or daylight a negative which has been developed and intensified with pyrogallic acid, fixation taking place after drying. The negative must be thoroughly washed before exposure to light, and with ordinary care there is little danger of fogging.

Illumination of the Copy should be perfectly even, a front light being made use of, and direct sunlight if possible. The latter is seldom admitted direct into the studio, and against outside work wind and rain are almost fatal objections. Where much copying has to be done it will be found an advantage, if at certain hours of the day the sun shines direct upon the studio, to remove all blinds, screens, or other obstructions, and so allow the rays to fall direct upon the print or drawing to be copied.

A Side Light, particularly if direct sunlight, must be avoided, as any unevenness or grain of the paper will be exaggerated and rendered more apparent if lighted in such a manner.

Under Exposure, if slight, is a fault much to be preferred to an error in the opposite direction.

New Transfer Paper for Photo-lithography.—In the photographic office, Calcutta, a new method of preparing the photo-lithographic transfer paper with arrowroot has quite recently been introduced, which, as is said, has the advantage of being much cheaper than the method of coating with gelatine usually adopted, and of giving results quite as good, if not even better, than by the old proofs. Bank post paper is coated in the usual way with two coats of the following mixture:—

Arrowroot140parts
Bichromate of potash70”
Water3,500”

After exposure to light, the prints are coated with transfer ink in the press as usual, the transfer ink used being composed of—

Hard re-transfer ink (plate to stone)100parts
Lithographic chalk ink100”
Palm oil7”

After inking in the prints are washed off with hot water, hotter than is required for gelatine transfers. The arrowroot transfer prints are found to go down well on the zinc without sticking, and give clear, sharp transfers.

Gelatine Plates have hitherto been considered almost useless for photo-lithography. Messrs. Mawson and Swan, however, have recently introduced a special make, known as the “Photo-mechanical” plate, which gives negatives of great density, and at the same time clearness in the shadows. The makers recommend the ammonia-pyro developer, with meta-bisulphite of potash. It will be found of considerable advantage if, before proceeding with the development, the plate be submitted for one minute to a bath of water 2 ounces, gallic acid 6 grains; this, without prolonging the development, will add considerably to the density of the resulting negative.

CHAPTER XX.

Application of the Carbon Process to Photo-lithography.

AN Ingenious Process, capable of yielding satisfactory results, is one in which a carbon print is transferred to and developed upon the stone direct. Such operation will present no difficulty to those familiar with the details of the process. In the “Photographic Archives,” vol. 17, page 193, are to be found working details, and it is there shown that by this method it is possible to directly transfer to stone pen and ink sketches, impressions from woodcuts, or copper-plates, without the necessity of a photographic negative. This process may, therefore, be available in cases where anastatic[W] printing is not applicable.

[W] The anastatic process consists in reproducing by zincography a copy of any recently printed matter. The subject for reproduction is moistened on the back with dilute nitric acid. It is then laid face downwards upon a freshly polished sheet of zinc and passed through the press. Printing is then proceeded with as in zincography. A lithographic stone may also be used, if, before laying down the impression, the face is moistened with turpentine, and allowed nearly to dry.

To those unacquainted with carbon printing it may be pointed out that it is a most valuable process, affording great facilities for the reproduction and reversal of negatives for Collotype. A knowledge of the process is here presumed, as it would necessitate too wide a digression to give an ample idea of the many useful applications of this beautiful and permanent method of printing. Very complete instructions will be found in Dr. Leisegang’s “Carbon Process.”[X] As regards the application of this process to lithography, only pictures devoid of half-tone, such as drawings in line and dot or impressions from engravings, are suitable for reproduction by this method, if upon clean paper (not too thick) and printed on one side only. The sensitised tissue may be printed from the original by contact, in the printing frame, instead of producing a negative in the camera by contact upon a dry plate. Should it be decided to print direct from the copy surround the edges of the same with strips of black paper or tinfoil, half-an-inch wide, and in a weakly actinic light. So adjust the ordinary sensitised carbon tissue that its edges are about in the centre of the surrounding strips, care being taken that the edges of the tissue nowhere extend beyond them.

[X] Translated by R. B. Marston, and published by Sampson, Low and Co., Fleet Street, E.C. The “A B C of Pigment Printing,” published by the Autotype Co., Oxford Street, W.C., may also be recommended.

Expose to Daylight for a time, gauging the exposure by means of the actinometer. Probably it will be necessary to print till the 7 shows.

A Finely-polished Stone is dusted and adjusted in a horizontal position, and flowed over with cold water.

The Exposed Tissue is placed in cold water, and allowed to soak till quite limp. It is then placed face downwards upon the wet stone, covered with indiarubber sheeting, and squeegeed into close contact with the stone; allow to remain under pressure for half-an-hour to an hour.

Development is effected by pouring warm water about 100° F. over the back of the exposed tissue. So soon as the colour exudes around the edges of the paper backing, the latter may be removed, and the development proceeded with by continuing to pour warm water over the surface. Only a slight impression should remain—the lines showing the bare stone perfectly clear and clean. Allow the stone to dry in a cool, shady place without the application of artificial heat.

Roll Up with lithographic chalk ink until the surface presents a solid black appearance, stand the stone aside for a few hours to allow the ink to penetrate its surface, and then

Remove the Negative carbon print from the stone by means of a piece of woollen cloth moistened with a thin solution of gum. This takes some time, but it will be found that the fatty ink has penetrated where unprotected by the carbon negative, and has formed a complete positive.

Gum In, etch, and proceed as in ordinary lithographic operations. It cannot be expected that the operation, as conducted above, will produce the finest results; the drawing will usually require a certain amount of retouching at the hands of the lithographic artist, who will, however, often be saved a vast amount of trouble. It is obvious that if the proceedings, as described, be carried out, using, however, a photographic glass positive in place of the printed impression, the process will be found capable of giving much finer results, and the exposure will be very materially decreased.