Pinking of the high-lights points to the bath being too weak or becoming worked out.
Double Toning, i.e., the print shewing different colours, points to insufficient washing or uneven action of the toning bath, i.e., not keeping the prints moving, or too slow toning, or that the toning bath does not suit the brand of paper.
Blisters are usually due either to using a hypo fixing bath too strong, or passing the print from one solution to another of a markedly different temperature. Hence the importance of dissolving the hypo either in tepid water or some time before use. The best all-round temperature for working this process is between the limits of 60° and 65° F.
Tinting P.O.P.—The colours to be used may be the usual moist water colours by some good maker, or solutions of aniline colours. These latter may usually be dissolved in water and applied in thin washes. The surface of the print should be rubbed as little as possible. If water colours are to be used it will be found helpful to prepare the surface of the print with one or other of the following preparations.
| 29. | White (bleached) lac. | 1 | part. |
| Alcohol | 12—15 | parts. |
Apply evenly and quickly with a spray diffuser or with a broad soft brush, and let the print become nearly dry before applying the colours.
30. The white of an egg in twenty ounces of water. Shake well, then add ammonia drop by drop until the mixture just very faintly smells of it. Filter and brush over the surface of the print. In mixing the water colours also use this albumen solution in place of water.
Advantages of P.O.P.—As compared with ordinary albumenized silver paper the P.O.P. class has the advantage of giving more detail with marked transparency in the shadows. The operations are more flexible and the results are as permanent, if not more so, than those on albumen paper. The paper keeps in good condition for a longer time. The negative giving the best results with P.O.P. is one having delicacy rather than vigour, i.e., a long scale of gradation of delicate steps is well rendered. Printing takes place quicker with P.O.P. than with albumen papers. The cost of paper and materials is much about the same in both instances.
Notes.—In the glazed variety of paper the smooth shiny surface is the sensitive one, and, of course, goes next the negative in the printing frame. In the matt paper the sensitive side may generally be known by its tendency to curl inward, i.e., the concave or hollow side is the printing side.
Formalin may be used in place of alum for hardening the gelatine. Of the usual 40 per cent. solution of formalin take one ounce and dilute with ten or twelve ounces of water.