TONING P.O.P.
Of the two methods of toning and fixing prints on printing-out silver papers, one is to tone first and afterwards fix, and the other is to tone and fix at one operation, the second method saving much time and trouble,while capable of producing quite as good results. It is described under the heading Toning and Fixing Combined." For separate toning and fixing, the prints require first to be washed for about twenty to thirty minutes in several changes of water ; the first two changes should be made as quickly as possible, care being exercised to prevent the prints from clinging together. To prepare the toning bath, two solutions are necessary : A. Am. sulphocyanide . 52o grs. 120 g.
Water to . . 10 oz. 1,000 ccs.
B. Gold chloride . . 15 grs. 3.5 g.
Water to . . 31 oz. 375 ccs.
To prepare the toning bath, take 2 drms. of A, add 5 oz. of water, and then add slowly 2 drms. of B ; in ten minutes the bath will be ready for use. It will be sufficient for four whole-plate prints or sixteen quarter-plates. A proportionate quantity should be prepared for any other number of prints, allowing always / drm. each of A and B, and ti oz. of water for each whole plate print. The prints to be toned are placed in the solution and continuously turned over by lifting the lowest print and placing it on top until the desired colour is reached. They are then rinsed in two or three changes of water and fixed for fifteen minutes in the following : Sodium hyposulphite I/. oz. 165 g.
Liquor ammonia; . 5 mins. t cc.
Waterlo oz. 1,00o ccs.
. .
Take care to ensure free access of the solution to the surfaces of the prints, and to prevent them from clinging together. After fixing, wash the prints, in water frequently changed, for from one to two hours.
An additional method of toning P.O.P. is by means of platinum. The most satisfactory manner of working is by first toning with gold, preferably by the sulphocyanide bath, then, after a short washing, toning with platinum, washing again, and fixing.
An alternative plan is to use a self-toning paper, by which the operation of gold toning is avoided, and then the prints are washed, toned simply with platinum, washed and fixed. Or the prints may be toned first with platinum and then finished in a combined gold toning and fixing bath.
Formul for platinum toning baths are given under the heading " Platinum Toning " ; another is Potassium chloroplatinite 1 gr. 25 g.
Sodium chloride . . 10 grs. 2.5 „ Citric acid . . . 10 „ „ Water . . . .5-6 oz. 500-60o ccs.
Whatever method of toning is adopted, only sufficient of the working solution should be pre pared for the prints to be toned ; it should be used once, and then thrown away.