Julius Schnauss

Printing in the Press.

THE etching or damping and rolling-up of the Collotype plate presents difficulties which are greater even than those met with in the preparation of the plate. These remarks also apply with equal force in photo-lithography, and whoever stops at the preparation of the plates or the photo-lithographic transfer, and leaves the subsequent operations to be performed by another, should not be considered either as a collotypist or photo-lithographer. The whole success depends upon a succession of apparent trifles; many errors it is impossible, or at any rate difficult, to rectify, and great care should be taken that nothing is overlooked, or from some trivial cause the whole may result in failure.

Firstly, remove all adherent matter from the back of the plate, as the smallest amount of dried gelatine, particle of grit or other hard matter will suffice to cause the fracture of the strongest glass plate on the first application of pressure.

The Etching or Damping Solution in most common use consists of a stock solution of five parts water, one part liquid ammonia, three parts glycerine, and one-tenth part of nitrate of lime. For use add five or six parts of this solution to 100 parts of water, sufficient of this being used to well cover the plate when placed in a clean dish. Another reliable formula is one litre glycerine, 600 cc. water, chloride of sodium three grammes. Plates may be immersed in these solutions for a time extending from ten minutes to five hours, or they may be well flooded with it, wiped off, and dried with blotting paper.

The press having been examined, oiled, and put in thorough working order, the next consideration will be

Fixing the Collotype Plate, which may be performed in several ways. Immersing the plate in the etching fluid precludes the old method of cementing it on with plaster of Paris, or glue and whitening, but it may be fixed by adhesion to a bed of glass or a polished iron plate, or a special and somewhat complicated frame may be procured for securing the thick printing plate by means of adjustable clips secured by screws. Should the printing surface be upon a thin glass adhesion alone will be found sufficient, a few drops of water causing the printing plate to adhere to the thicker glass plate underneath. This method has the disadvantage that it is most difficult to ensure the position of the plate being in keeping with the mask on the frame. Should the mask be placed directly upon the gelatine surface of the plate it will not last many impressions without either tearing or causing damage to the surface through the formation of creases or wrinkles. If the picture has to be trimmed without margin, and mounted—either with or without varnish—the masking is altogether unnecessary. The preparation of the ink and rollers should next be proceeded with. Supposing the work in hand to be one of a simple character—say the reproduction of an impression from a copperplate in black—take a piece of the best chalk ink about the size of a hazel nut, in an unthinned condition, as supplied to the printing trade, and with an iron spatula or palette knife spread it upon the inking slab. Add one-quarter the amount of middle varnish (refined and odourless), one drop of olive oil, and one or two drops of best French turpentine, incorporate thoroughly by means of the palette knife, divide, and apply one-half to the roller. The next operation is the important one of

Distributing the Ink.—A really good leather roller, the handles of which should be encased with easy fitting leather covers, is most suitable for the purpose. The ink, by careful manipulation of the roller, should be gradually distributed over the entire surface of both roller and slab in a perfectly even and regular manner. Should any small lumps be observable upon either surface they should be carefully removed with the palette knife and the rolling and distributing again proceeded with, as on careful attention to this matter the excellence of the resulting print greatly depends. The printing plate being well secured, its moistened surface should be very evenly dried. This is best effected by means of a roller covered either with fine cloth or washleather, or a fine soft linen cloth may be used as a substitute.

Rolling up.—Apply the inking roller with light pressure to the nearest edge of the plate, and roll backwards and forwards over its surface several times; an experienced printer will at once perceive the condition of the surface. For the first inking a stiffish ink should be used, as the plate will not then so readily become dirty. By repeated rolling in different directions, and what is of equal importance, with varying pressure, endeavour to distribute the ink with perfect evenness, and with a view of producing a clear and vigorous inking, which will yield a similar perfect impression. It should be remembered that

1. A slow rolling with heavy pressure deposits ink on the plate; and

2. Light and quick rolling removes the ink from the print layer.

By modifying the treatment of the plate, and varying the application of the roller and damping solution, an experienced printer will demonstrate his power of producing from the same plate flat, weak, and unsatisfactory impressions, or prints as clear and vigorous as may be desired. The first application of the ink having been made with a leather roller, it should be distributed, and the half-tones improved by the application of a smooth roller, preferably of glue composition. Without this second inking, it will be found impossible to produce the highest results in half-tone.

The Second, or Composition Roller, must be lightly charged with ink considerably thinner than that applied in the first instance, the remarks concerning the pressure applied to the leather roller applying with equal force in this case. By light, quick rolling, the ink is partially removed from the plate, while heavier pressure and slower movement will deposit ink and strengthen the shadows.

When the inking is complete, the frame with the mask is placed in position. The printing paper, which may be either strong, well-sized letter-paper, thin cardboard, or the paper known in the trade as “dull enamel,” cut to a suitable size, is adjusted over the mask, and backed with a couple of thicknesses of smooth paper. This again is covered, with the tympan attached to its frame. Push the bed of the press so far under the scraper that the latter, when pressure is applied, will nip the plate about one centimetre from the commencement of the picture. This position has to be ascertained by trial before covering with the second or tympan frame.

The Scraper being regulated so that it will give a sufficient pressure, pass the bed quickly through the press to the extent necessary to produce a complete impression. The length of traverse of the bed during printing can on most presses be regulated by side screws, or the tympan may be lightly marked. After releasing the pressure, the bed is withdrawn, the tympan and masking frames thrown back, and the printing paper cautiously raised by one corner. It often adheres slightly to the printing surface, and this is usually an indication of a good plate. The adhesion may, however, at times be so strong as to tear the paper, or, in the case of enamel paper, remove the chalk coating. As previously mentioned, the scraper should be selected of a width somewhat exceeding that of the picture, but never exceeding that of the glass plate. It may be left plain and moderately sharp, or covered with leather.

Damping the Plate between each impression will usually be unnecessary, providing a good sample of gelatine is used, and the damping solution contain a sufficient quantity of glycerine. In cases where the Collotype plate has been over exposed, or the subject be one which requires an absolutely white background, damping between each impression will be absolutely essential. Where it is omitted for any length of time, the whites of the pictures will always be more or less degraded or tinted. Should the early impressions not be satisfactory, patience should be exercised, and by careful treatment with the roller or rollers, and care in the damping, favourable results will often ensue after the first few impressions have been pulled. Only from actual damage to the print layer, or excessive over exposure in the copying frame, need the plate be placed aside as in a hopeless condition. The beginner should guard particularly against mechanical damages in damping; drying and rolling. Lithographers are inclined to treat the delicate printing surface with the same vigour and energy that they would apply to the more substantial lithographic stone to which they are accustomed.

The following directions from “Kleffel’s Manual of Photography” are to be recommended in printing line subjects, particularly in “glass” printing direct from the negative:—“The chromated layer of gelatine must have been submitted to a sufficiently long exposure to ensure it taking the ink over the whole surface. For the first rolling in of the plate, the ink should be composed as follows: White wax, 45 parts; middle varnish, 5 parts; gum elemi, 15 parts; litho ink (about 5s. per lb.), 20 parts.

“After the plate has been thoroughly rolled in and blackened, it must be rubbed with a piece of unbleached muslin, previously saturated with the following solution: 30 parts of ammonia and oxgall (about equal parts), 30 parts gum arabic, 90 parts water, until the picture develops perfectly clear. Dry with a clean piece of muslin, and roll in for the printing proper with ordinary thin copper plate printing ink. Plate paper, similar to that used in printing from the copper plate, is most suitable.”

When printing operations are complete, the rollers, printing plates, and inking slabs should be at once cleaned, as the varnish colours soon harden and create difficulties.

Cleaning Leather Rollers without damaging them requires considerable practice. They are always scraped with a clean knife, and the operation should be performed in one direction, to ensure which it is advisable to mark one of the roller handles. Leather rollers not in constant use, before being put aside, should have their surfaces carefully and thoroughly rubbed over with tallow, which must, of course, be scraped off before the roller is again used.

Cleaning Composition and Indiarubber Rollers should not be effected by means of scraping, but their surfaces should be cleaned with turpentine, applied with a linen rag free from lint.

Cleaning the Plates.—Turpentine is used to free the surface from every particle of ink, and after the thorough evaporation of the spirit, the plates should be well washed in water to remove all trace of the damping solution, dried, and stored in a cool place. It is sometimes a matter of difficulty to remove ink from Collotype plates that have been printed from, but a simple method is to pour over the plate—as in developing a collodion picture—some lukewarm water. This will dissolve a thin layer of gelatine, and enable one to at once proceed with the work.