Julius Schnauss

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.

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.

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.

Transposing—Black and White.

A modification of the foregoing process may be utilised for the reversal or transposition of black to white, or vice versa, of any subject of which a print may be obtained in printing ink.

An Impression is first obtained either upon sensitised carbon tissue or, preferably, on a thinner paper, coated and sensitised as for photo-lithography. Such paper must not be submitted to a light of much actinic power during or before printing, and as much ink as possible should be used without risk of filling up the work.

Dust Over the impression while still wet any dense opaque colour, applied by means of wool or camel-hair brush, carefully going over every part and piling on as much colour as possible, after which

Expose the Paper bearing the print so treated to the light for a short period, dependent upon the light and sensitiveness of the paper. If it be a full impression, well dusted, the latitude in exposure will be very considerable. Ink Up the whole surface of the paper with lithographic transfer ink, thinned with turpentine, and applied by means of a sponge or roller.

Develop, as in photo-lithography, either by means of warm or cold water, according to the coating upon the transfer-paper. The sensitised paper, where protected by the ink impression, has not been hardened by the action of the light, and readily parts with the ink and colouring matter. If the impression has been one from ordinary type it will now show in the form of white letters on a black ground.

Transfer to Stone, and otherwise treat as an ordinary photo-lithographic transfer.

Engraved Negatives for Photo-lithography.

In certain processes for the production of photo-relief blocks many operators prefer artificial negatives, in the production of which photography has played no part, but which are, on the contrary, the direct production of the artist’s hand.

Factitious Negatives may be produced by coating a plate with a transparent but non-actinic coating, and by removing or erasing in a suitable manner designs may be copied without the use of a camera or lens. Professor Husnik and others have published different methods whereby the artist is enabled to transfer the creations of his pencil to zinc or stone, without resorting to the aid of the photographic negative process, although the subsequent operations may still entitle it to be styled photo-lithography.

The process most likely to lead to success consists of first coating a glass plate with a strongly iodised collodion, sensitising as usual, well washing on both sides and drying. To engrave, lay the plate upon a black cloth, and the design may be traced and engraved upon the surface by means of etching points or needles. Remove all loose particles of collodion from the plate by gentle brushing when the drawing is completed. Immerse the plate a second time in the silver bath, and develop with either pyrogallic acid or sulphate of iron developer.

Husnik proposes to first coat the plate with a solution of pure fuchsin, and afterwards with one of gum, and then engrave as previously indicated.[Y]

By either of these methods negatives of extreme density and absolute clearness in the lines may be produced and used for obtaining impressions in ink, the transfer of which to stone presents no difficulty.

It remains to be added that there are several methods of producing grained negatives for photo-lithography in half-tone, and therefrom a transfer for stone, and so obtaining impressions at a much greater rate than is possible from a Collotype plate. They may each produce results with a certain amount of success; but even those from the best methods indicated cannot be compared with Collotype. The too obtrusive grain of the half-tone pictures so produced destroys much of the finer details, and it is to be regretted that all such processes leave so much to be desired.