Julius Schnauss

Other Collotype Processes.

THE Artotype Company, of New York, which has acquired Obernetter’s process, proceed on somewhat different lines to those laid down in this work, and an abstract of their proceedings is here given as interesting to those about to experiment. According to Bachrach, “Photographic Archives, 1879,” p. 66, they proceed as follows:—

Plates coated with Husnik’s silicate of soda substratum are dried rapidly in a box heated to 65° C. This causes the solution to coagulate, the plates are dried in half-an-hour, and as it adheres with great tenacity to the glass plate, the latter may be at once coated with the chromated gelatine solution, or it may be kept till the next day. Before the second coating is applied the plate is well washed and allowed to dry spontaneously. The drying-box is of wood, 2-1/2 feet square and 5 feet high, the entire front being a large door, as shown in the sketch (fig. 9), and the bottom a flat water tank about four inches deep fitted with two pipes, one to allow the escape of steam, and the other of use in filling the tank with water. It may be heated by means of gas or a petroleum lamp. After the bottom of the box has been accurately levelled, it is covered with a few sheets of blotting paper, on which are placed the albumenised plates. Occupying the upper part of the box are adjustable racks, on which other plates are dried. The box is heated to 82° C., the plates are levelled in their places, and just sufficient hot chromatised gelatine solution poured on each to spread up to the edges—not more. The Artotype Co. takes one-third each of gelatine, isinglass, and the so-called Magdebourg isinglass. Plates are allowed to remain in the drying-box about 20 to 30 minutes, during which time the door must not be opened, and particular importance is attached to the high temperature, reaching even to 93° C., at which the drying is completed, as it is considered by these means printing plates of much finer grain are obtained. (The Author believes the temperature given is much too high, as it would be sufficient, without exposure to light, to bring about a partial decomposition.) When dry, the plates may at once be printed under the negative. To etch the plate it is immersed in a solution of 5 gr. alum in 1 litre of water, rinsed, allowed to dry, and put in a bath consisting of 150 ccm. of water, 1 litre of glycerine, 300 ccm. of ammonia, 30 g. nitrate of lime. Plates that have been exposed under the negative too long are treated with a solution of 20 parts of ammonia, 20 parts of glycerine, and one part of Venetian turpentine; with this they are flooded. The remainder of the process is very similar to that already described.

Seignior Carlos Relvas.—Vidal publishes the following method of procedure as that adopted in the studio of this eminent Portuguese amateur collotypist, where it was introduced by Jacobi:—Very thick glass plates, finely ground on one side, are used; they are cleaned with nitric acid, and rinsed in distilled water. The drying box used is provided with iron bars, fitted with adjustable screws for the purpose of accurately levelling the plates. Midway between the top and bottom of the box is an iron plate, underneath which are fitted gas jets. The doors by which access to the box is gained for the plates consists of very fine wire gauze, allowing the escape of steam, but preventing the access of insects. After a thorough cleansing, the plates are levelled on the adjusting screws, allowed to thoroughly dry, and then coated on the ground side with the following solution—

To which is added sufficient ammonia to give the liquid a pale yellow tint, somewhat less being used where a hard negative is to be employed. This substratum is filtered, and the plates afterwards coated and placed upon the levelling screws in the drying box, which is heated to a regular temperature of 40° C. In about two hours the plates will be dry, and are then placed, coated side downwards, upon a black cloth, the back of the plate being exposed to diffused light for half-an-hour. It is again placed in the drying box, and the second coating, as follows, applied—

The preparations A and B are as follow:

To each square decimetre of surface should be allowed 2 ccm. of the above solution. The plates are replaced in the drying box, which is heated to 45° or 50° C. They should be dry in three hours, and are then ready for printing under a negative in the copying frame. They are afterwards well washed in filtered water, and allowed to dry spontaneously in a dust-proof situation. In two or three days the printing may be proceeded with, the surface having been softened by allowing the plate to stand for seven hours in the following solution—

All solutions are filtered through flannel. From the face of the plate the superfluous moisture should be removed with a sponge. A very thick glass plate is fixed to the face of a lithographic stone by means of glue and whiting, and adhesion is secured between the face of the thick glass plate so fixed and the back of the Collotype plate by means of a few drops of water. The whole, so arranged, is placed upon the bed of the press. Should the prints lose their contrast while the printing is in progress, they are lightly sponged over with a sponge dipped in the last-mentioned solution. If this fails to produce sufficient effect, the plate is first washed with turpentine, and then with the glycerine solution. Care should be taken to prevent the two liquids becoming mixed on the plate, to prevent which different sponges and drying cloths should be used.