RESINISED PAPER (Pr., Papier resini ; Ger., Harzemulsionspapier) The use of resin for photographic paper was first suggested in 1863, and the method adopted was to make an alcoholic solution of resins with a chloride and brush this over the paper or immerse the latter in the solution, dry, and sensitise subsequently by floating on a solution of silver nitrate. Three years later an aqueous solution of shellac in borax or sodium phosphate was used. Later still, Cooper suggested the emul sification of bleached shellac in gelatine. In 1891, Valenta suggested the following method of work ing, which gives excellent matt surface prints :— Hard gelatine . . 35o grs. 8o g.
Soak in water for half an hour and drain well.
Pale French resin . 35o grs. 8o g.
Liquor ammoniR . q.s. q.s.
Distilled water . . to oz. t,000 ccs.
Powder the resin, rub up with the ammonia and a little water, add the rest of the water, boil, and add ammonia from time to time till a dear solution is obtained. Add the gelatine, stir till
dissolved, and add— Ammonium chloride . 88 grs. 20 g.
and filter. Finally add enough saturated solu tion of citric add to give a strong acid reaction. The acid precipitates the resin as an impalpable powder, which is suspended in the gelatine. The paper should be brushed over with the solution and then floated on the surface for three minutes and dried, and then sensitised in the usual way by floating.
A variant was suggested by E. J. Wall, and consisted in the use of an ammoniacal alcoholic solution of resin, which was added to an ordinary gelatino-chloride print-out emul sion. These papers are particularly suitable for platinum toning, and give fine black tones.