SILVER INTENSIFIER The silver intensifier has the advantage that the density is under control, and either little or much intensification can be given. The film should be hardened in a io per cent. solution of formalise for three minutes and then washed in water. Wellington's formula (1889) is : A. Silver nitrate . 120 grs. 28 g.
Water (distilled) . 2 oz. 200 ccs.
B. Ammonium sulpho cyanide . . 240 grs. 56 g.
Water . . . 3 oz. 30o ccs.
Add B to A, and keep in a dark place. The bottle is shaken immediately before use, and some of the liquid poured into a vessel. A strong " hypo ' solution is then added very slowly till all but a trace of the precipitate has dissolved. To each ounce of this solution 3 grs. of a ro per cent. stock solution of pyro (preserved with sodium sulphite) and 4 mins. of liquor ammoniac are added, and the solution poured upon the plate and allowed to act until the desired density is obtained. A few drops more of ammonia may be added if the action is slow in beginning, but too much will spoil the bath by precipitating the silver. The plate is then refixed for ten minutes in an ordinary " hypo " bath and then well washed. As the intensifier contains " hypo," a prolonged washing is not necessary after the first fixing and previous to intensifying. Many modi
fications of the above formula have appeared, but all are much alike in the results they give. Some workers recommend the rinsing of the intensified plate in a bath of 6 mins. of hydro chloric acid and r oz. of water before re-fixing, using an alkaline fixing bath.
For Farmer's silver intensifier, solutions of oz. of silver nitrate in 12 OZ. of distilled water and 1 oz. of potassium bromide in 2 oz. of dis tilled water are mixed together, and the pre cipitate is removed, washed with water, and stirred into a solution of 2 oz. of " hypo " in 6 oz. of water. In a few hours' time, filter and make up to 16 oz. with distilled water. In this immerse the negative for five minutes, and then develop with ferrous oxalate or with a pyro silver bath, consisting of pyro, 4 grs.; distilled water, 2 oz. ; silver solution, ; and ro per cent, solution of •880 ammonia, 3o mins.
Wellington's improved formula (r91r) is given under the heading " Wellington's Silver Inten sifier." For Monckhoven's intensifier, see under its own heading.