Wash for five minutes and fix in bath 23.
Intensifying and Reducing P.O.P.—When the negative is obtainable and printable it is very much better, and altogether more satisfactory to make a fresh print than to attempt to intensify or reduce an unsatisfactory one.
Nevertheless, it sometimes happens that this course is not possible, and the best has to be made from an unsatisfactory print.
If the print is only very lightly printed, and comes straight from the printing frame, it is best to strengthen it by development (see [formula 17] et seq.). If the print has been toned and fixed, etc., the following may be tried:—
26. Make a saturated solution of mercury bichloride in cold water, let it settle, and use only the quite clear supernatent liquid. Immerse the print in this for 15 minutes, turning it from time to time, and see that no air bells are clinging to either side. Wash the print in running water for 15 minutes at least, and longer if convenient. Then immerse it in a bath consisting of strong ammonia one part, water ten or twelve parts. Again wash for five minutes under the tap.
Reducing P.O.P.—
| 27. | Hypo | 120 | grains (120·) |
| Uranium nitrate | 4 | " | |
| Water | 2 | ounces. |
The advocates of this solution claim for it that it can be used either before or after toning with equal facility and advantage. Prints must be well washed both before and after its use in any case.
Another method, which is somewhat risky except in expert hands, is as follows:—
28. Dissolve metal iodine in alcohol to a rich dark port wine colour. Dilute a small quantity with cold water until the whole is a pale sherry colour. Now prepare a one in ten solution of potassium cyanide (N.B.: a powerful poison) and add this a little at a time until the pale yellow colour of the iodine solution is just discharged.