Julius Schnauss

Finishing and Varnishing Collotype Prints.

RETOUCHING Prints.—Under the above heading Leon Vidal, in his work “TraitÉ Pratique le Phototypie,” gives the following directions, which I reproduce from the “Photographic Archives.” Even with the utmost possible care in the preparation of the printing surfaces there will be required in most impressions a little retouching, if only to hide a few white spots. In large orders this cannot be carried to the extent it is in silver prints. It happens in printing that particles of dust find their way to the plate, and cause either light or dark spots in the impressions; the former are covered by touching with ink, the latter are removed with the erasing knife, and the white spot resulting from the operation is toned down with ink. This spotting is quickly performed. The paper being dull a colour should be used containing only a small proportion of gum; it will then be invisible. Prints which it is intended to varnish should not be spotted until they have been sized, unless printed upon a paper already impervious to the varnish. The colour most suitable of all is the actual printing ink thinned with turpentine, by using which the trouble is avoided of mixing any special colour to match the tone of the impression, as the two colours are necessarily identical. Another advantage gained by adopting this method is that the spotting may be completed before sizing, as the aqueous solution of gelatine will not cause it to run. For impressions in pure black the lithographic chalk is probably the best medium for correcting proofs, as the colouring matter will be found to well harmonise with the general appearance of the picture. A blacklead pencil, on the other hand, is quite unsuited for the purpose on account of the highly metallic appearance visible wherever the pencil has been applied to the print. Retouching or spotting should not extend beyond the removal of light and dark spots; the correction of larger faults should not be entertained, but a fresh printing surface produced. Faults present in the original negative should be carefully retouched and removed or reduced as far as possible. Should the white margins of the picture become soiled by contact with the inky mask or by finger marks, they may be cleaned with indiarubber ink eraser. The backs of impressions may also be cleaned in the same manner.

When copies have to be mounted on cardboard they may be either left with a matt surface or varnished. In the first case, the edges are trimmed, and they are then mounted upon the cardboard mounts. If the latter have been previously damped they will retain their flatness. Rolling or Burnishing must not be done until the prints have completely dried, or the picture may be torn from the mount.

Sizing and Varnishing.—Prints to be varnished may be printed on prepared or sized paper, and in such cases may be at once varnished. If, on the contrary, the paper is not sized, they require a special preparation, as follows:—A 10 per cent. solution of gelatine is laid on with a broad camel-hair brush, avoiding air bubbles and streaks. After a little practice this operation will be found both easy and rapid. The sized pictures are pinned in pairs back to back on a wooden frame, to which strips of cork are attached; when the prints are quite dry the operation of varnishing may be proceeded with. A good varnish, probably the best for the purpose, which possesses the double advantage of remaining colourless and setting very hard, consists of a solution of 15 parts of white (bleached) lac in 100 parts of wood spirit (vegetable or wood naphtha). On dissolving the shellac it will be found that the solution is clouded on account of the suspended fatty matter, the removal of which is always desirable; the varnish will then filter more rapidly and give a more glossy coating. By adding powdered lime three parts of the solution may be decanted clear, and the remainder may also be used after filtration through felt. Or if to three parts of varnish one part of benzine or petroleum ether be added, the solution will resolve itself into two layers, and the upper one, which will contain the fatty matter, may be poured off. The varnish is best applied by means of a ball or dabber, care being exercised to avoid air bubbles; the print is next placed in

The Drying-box (see fig. 8), which is a four-sided tin box 1 m. long by 0·25 m. high. A gas-pipe, perforated with small holes drilled about 6 to 8 cm. apart, runs through the upper part of the box, the front of which is open to two-thirds its height. A plate, finely perforated, divides the upper third from the lower two-thirds, and forms an inner division, through the upper of which the gas-pipe passes. The flat perforated division is hinged to allow of being opened for the purpose of igniting the gas. The pictures placed on the bottom of the box dry very rapidly, while the perforated division prevents the possibility of the ignition of the vapour of the spirit employed. With such an apparatus it is possible to varnish and dry a large number of prints in a very short time.

Sizing may be Avoided if each picture, after well drying, be dipped into the following solution: Water 500 g., borax 130 g., white shellac 100 g., carbonate of soda 6g. The borax and carbonate of soda are dissolved in boiling water, and the powdered shellac then added in small quantities; when solution is complete carefully filter and allow to cool. The impressions, two and two, back to back, are pinned on frames, dipped in the varnish, and afterwards dried. By this procedure a shellac coating is given to the surface only of the print; there is no gelatine substratum to soften through atmospheric influences, and so crack and destroy the layer of varnish. In winter the temperature must be kept high, and the solution should be heated 15° to 20° C.

Parchmentising to a slight degree may also be adopted to close the pores of the paper. Add one part by volume of water to two parts of sulphuric acid, allow it to become quite cold, immerse the pictures for one second only, and at once wash in a copious supply of clean water to which has been added a small quantity of ammonia to effectually neutralise the acid. The action of the acid must not be carried too far, as it is merely necessary to act on the surface. To prevent paper so treated from cockling while drying, it must be put under pressure or stretched upon a frame; when quite dry it has to be varnished and dried by heat.

Varnishing Enamel Paper without previous sizing is best done by means of an alkaline solution of shellac prepared as follows: Place in a six litre tin flask 1/2 kilo of bleached and powdered shellac, pour over it 1-1/2 kilo of alcohol and 1-1/4 kilo of strongest ammonia. In the course of a few days the solution of the shellac will be complete, then add, with constant stirring, 2-1/2 kilo of hot water, and when cold filter. It may be applied to the print with a broad Blanchard brush,[K] and left to dry in a horizontal position. The prints may also be floated on the varnish for about half a minute, and then suspended to dry by means of clips. After a few minutes have elapsed a piece of blotting paper should be applied to the bottom edge to absorb the superfluous varnish.

Rolling or Burnishing must on no account be attempted until the mounted prints are perfectly dry, otherwise they may be seriously damaged or even completely torn from the mounts.