Reduction of Over-Exposed Prints.
Mr. England writes as follows to the Photographic Journal, and we can unhesitatingly say that the method of reducing an over-printed proof is excellent.
"A simple and certain method of reducing over-printed proofs has been one of the wants long felt by all photographers. It is well known that in every photographic establishment even the most careful printers cannot always be sure of getting the exact depth of tone required, and proofs occasionally get over-printed. Of course prevention is better than cure; but, when a remedy is necessary, the method I am about to describe answers admirably. I tried a great many experiments before I succeeded to my satisfaction. I found that cyanide of potassium totally destroyed the print, even when used moderately strong. By using a weaker solution it was well under control, and the exact depth could be readily obtained; but during the washing to remove the cyanide the action of the latter continued, and spoiled every proof. I then tried several methods to arrest the action of the cyanide, but without success. It then occurred to me to use the cyanide in such a weak state that but little should be held in the paper, only sufficient to reduce the print to the required depth; for this purpose I made a bath of only four drops of saturated solution of cyanide to a pint of water. The prints immersed at first showed no signs of getting lighter, but after about an hour the most perfect results had been obtained with prints considerably over-printed. With lighter pictures a less time is required. Proofs treated in this way lose nothing of their tone during the after-washing, which should be thoroughly done, and, when dry, retain all the brilliancy of an ordinary print."
The plan of using cyanide has, we know, often been proposed, but with no success until, we believe, Mr. W. Brooks gave a formula which worked successfully with him.
Another plan, proposed by Mr. L. Warnerke, for effecting the same thing is the use of ferric sulphate. A weak solution is prepared, and the print immersed in it. The reduction takes place rapidly, but evenly.
We need scarcely say that it is better not to have to use either of these remedies, by avoiding over-printing; but as mistakes will occur, it is evident that the above will be of use at times.