Bromoil printing and bromoil transfer

by Emil Mayer

The bromoil printer obviously does not need all these. One representative of each group will be quite sufficient, and I should state that when colors are obtainable in both light and dark shades, the light one should always be chosen.

The colors must be very finely ground; it will not be necessary, or only exceptionally, to prepare the powder colors oneself, for they can be obtained commercially in every high grade store dealing in painters’ materials. If, however, this becomes necessary, then the lumps of color should be crushed on a stone or glass with a flat muller, and the coarse granular masses thus formed kneaded with a little water, or, better still, some alcohol and then thoroughly ground. The mass should be allowed to dry thoroughly and the process repeated two or three times. The finer the powder is rubbed up in this way the finer the tone it will give. The coarse color powders, often found in drug stores, are not suitable for our purpose; they are used more for industrial purposes.

Aniline colors, or those brightened with anilines, should be absolutely avoided, as they stain the gelatine and thus spoil the print. On the other hand I call the attention of all bromoil printers to the pastel colors, which can be used with excellent results. They offer many advantages over the powder colors, since among the hundreds of color shades, in which they can be obtained, it is easy to choose that which is most suited for the subject. The tints are ready to use, while with the powder colors the desired tint can only be obtained by mixtures. These colors have the further advantage of covering much more strongly, even to obtaining brush texture; they are somewhat more difficult to apply to the print, because of the fact that they are mixed with a medium which is from its nature not so well adapted to our process. Those, however, who have well mastered the brush technique, will easily overcome this small hindrance.

If the pastel colors are used one should only take those of reliable manufacture, such as those made according to Mengs’ formulas, which are everywhere obtainable under the name of Meng’s pastel pencils, though this does not mean that those of other makes will not give excellent results.

The Rubbing Plate.—For this we use a thick plate glass slab, ground on one side, about 15 by 20 cm (6 × 8 in.).

Pestle or Muller.—A pestle of glass is the best. The head must be round, not flattish, and have a matt surface.

Spatulas.—It is necessary to have a flexible spatula (palette knife) about 1 cm (⅜ in.) wide and a stiff one, an ink or putty knife, about 4 to 5 cm (1½ to 2 in.) wide.

Now that we have become conversant with all the necessary materials, I come to the:

Practice of Ink Grinding.—As I have mentioned above, the purpose of the work is to obtain an ink of as stiff a character as possible. To this purpose, after the vessel in which the varnish is kept has been allowed to stand at least 10 minutes in hot water, or an hour in winter, we remove from it by means of a wood or glass rod a very small quantity of the varnish, spread it on a glass plate and rub it with the pestle so that it covers a surface of 3 to four qcm (½-¾ sq. in.). To the varnish thus spread out we add with the flexible spatula a small quantity, about as much as will lie on the end of a pocket knife blade, of the powder color and rub it with the pestle until certain that the color is absolutely mixed in. If too little color has been taken, more should be added and rubbed again until a firm doughy mass is obtained which has a slaty and not oily gloss, and can scarcely be worked with the pestle. Now with the springy spatula the whole ink mass is pushed together from the edges to the middle to make a little heap, and the ink that remains on the pestle scraped off and added to it; the whole mass should then be again worked up with the pestle and this procedure repeated two or three times. Then the ink is ready. It must be so hard that a brush set into a small quantity of the ink that has been taken from the heap with the stiff spatula and spread out in a thin film, neither takes up the ink nor gives it up again to white paper. In order to make it fit for use, one must add to this thin film one small drop, not more, of pure linseed or poppy oil, petroleum, light copper-plate printing varnish, or medium, and mix it well with the ink with the stiff spatula. Petroleum can be highly recommended for the softening medium. One can use the ordinary lamp petroleum, but the so-called purified petroleum is better. It ought only to be added to the ink drop by drop. Now the brush will take up and give up the ink. If it should not be sufficiently soft, the procedure should be repeated, but always carefully, so that too much linseed oil is not added and thus the ink made too soft. If we use the pastel instead of the powder colors it is not necessary to break these up first. Small pieces broken from the pencils dissolve readily in the varnish. It would seem permissible to assume that the whole work of dilution with linseed oil could be saved by not adding so much color to the varnish, but by proceeding with the inking-up as soon as the ink is taken up by the brush, but this is not the case.