Photo-Lithographic Transfer Paper.

Photo-lithographic transfer paper and ink are prepared in the following manner:—The paper is treated with a solution of a hundred parts of gelatine and one part of chrome alum in 2,400 parts of water. After drying, it is treated with the white of egg. It is made sensitive with a bath consisting of one part of chrome alum, 14 parts of water and 4 parts of alcohol. The latter ingredient prevents the white of egg from dissolving. On the dark places the white of egg, together with the ink with which the exposed paper has been coated, separates in water. The transfer ink consists of 20 parts of printing ink, 50 parts of wax, 40 parts of tallow, 35 parts of colophony, 210 parts of oil of turpentine, 30 parts of Berlin blue. It is found that a varnish formed of Canadian balsam, dissolved in turpentine, supplies a most valuable means of making paper transparent. The mode by which this is most satisfactorily accomplished is by applying a thin coating of this varnish to the paper, so as to permeate it thoroughly, after which it is to be coated on both sides with a much thicker mixture. The paper is kept warm by performing the operation before a hot fire, and a third and even a fourth coating may be applied until the texture of the paper is seen to merge into homogeneous translucency. Paper prepared according to this process is said to come nearer than any other to the highest standard of perfection in transparent paper. Care must be used in making, as the materials are highly inflammable.