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Screen-Plate Practice 527
bath, washed and redeveloped with an amidol developer or treated with 5 per cent solution of sodium bisulfite.
E. J. Steichen9* avoided intensification as far as possib/e, as he considered that this was the cause of the glaring colors so often seen in Autochromes. When required, he preferred the Agfa intensifies which is a solution of mercuric sulfocyanide. A. David95 had recourse to the chromium process, using :
Potassium dichromate 20 g.
Hydrochloric acid 20 ccs.
Water 1000 ccs.
The plate should be immersed in this for from 30 to 60 seconds, washed and immersed for not more than 30 seconds in a 3 per cent solution of bisulfite, so as to remove any yellow stain, and then redeveloped with an amidol developer.
"Anon"90 suggested the use of lead ferricyanide. The plate was to be bleached in this, dipped for 15 seconds into a 2.5 per cent solution of hydrochloric acid, washed and blackened in a 2.7 per cent solution of sodium sulfide, again immersed in the acid bath, washed and dried. The permanence of the result is doubtful.
Fixing. — After intensification the plate should be washed for 30 seconds, then treated to a clearing bath of :
Potassium permanganate 1 g.
Water 1000 ccs.
For from 30 to 60 seconds, then washed for the same time and fixed in :
Sodium hyposulfite 150 g.
Sodium bisulfite lye 50 g.
Water 1000 ccs.
And washed for 5 minutes. R. Namias considered this bath was too strong and very liable to dissolve the intensification and preferred a 3 per cent solution of hypo. Sometimes the above clearing bath causes brown stains, and he proposed97 the use of a 0.2 per cent of oxalic acid after it. E. Konig98 suggested for the same purpose a very dilute solution of sodium bisulfite, and this had the advantage that if it was not washed out, it would do no harm when the plate was placed in the hypo.
G. Muller™ pointed out that one common failure was the practical disappearance of the image in the fixing bath, and the plate was usually given up for lost. But if physical intensification was resorted to, full intensity might be obtained, although it sometimes took a long time. Neuhauss' old formula was recommended :
Ammonium sulfocyanide 24 g.
Silver nitrate 4 g.
Sodium sulfite 24 g.
Hypo 5 g.
Potassium bromide, 10 per cent sol 6 drops
Water 100 ccs.