PHOTOTINCTURE Villain's process, invented in 1891, for the production of photographs on fabrics and paper by means of dyes. The fabric is sensitised by a few seconds' immersion in a solution of Ammon. bic.hromate . 5 oz. 55o g.
Ammon. vanadate . 240 grs. 55 „ Water . . . 10 oz. i,000 ccs.
The material is dried in the dark at a temper ature not exceeding (24° C.), for at 85°P. (29° C.) the transforming action begins and shows itself by veiling the whites. The dried material is exposed to daylight under a negative, the time being found by experiment, the image being visible, and washed to eliminate the chromium salt not acted upon by light, leaving the fabric mordanted where exposure has fixed upon it the chromium and vanadium oxides. Next the fabric is boiled in a dye bath, preferably of alizarine or purpurine, this being gradually heated to boiling point, at which it is maintained for fifteen minutes. The fabric is then washed and, if the whites are not pure, passed through a warm bath of soap and sodium carbonate, or a cold bath of chloride of lime to which has been added a few drops of hydrochloric acid, it being necessary before drying to drive out every trace of the acid by the use of a bath slightly alkaline.
The fabric is finally washed and dried. The dyes fix themselves only on the parts where the mordant is fixed ; and the parts where the light has not acted (high lights) will give the whites, unless the materials were impure or a mistake has been made. The colouring products used by Villain were the artificial alizarine sold under the name of alizarine for violet, alizarine for red ; alizarine blue S ; alizarine black S ; gallo Ravine ; purpurine ; anthracene brown (antho gallop ; alizarine orange ; alizarine yellow A ; alizarine chestnut ; alizarine green S ; alizarine blue indigo S, and galleine.