The soft, delicate negatives, of which the best professional portrait negatives are a good sample, yield the best possible results, whilst with the CC paper, negatives so thin and delicate as to be suitable for hardly any other printing process, give all that can be wished for.
Much, of course, will depend on the kind of print desired and the paper used, and here it may be remarked that from a given negative the different kinds of platinotype paper give different results.
From a given negative the hot-bath papers yield the greatest amount of half-tone, the hot development tending to yield flatter results. Next comes the smooth, cold-bath paper, and finally as yielding the maximum amount of vigour is the CC paper. Hence if we make our negatives specially for our chosen printing process, a stronger negative will be needed for S, RS, A and C than for the AA and CC, whilst for the latter a negative distinctly erring on the side of extreme thinness will be best.
If a negative gives prints which are too weak and flat for our purpose, a great improvement may be effected by printing through blue glass. If on the other hand the prints are too hard and harsh in contrast, it is advisable to print through "signal" green glass.
TONING PLATINOTYPE PRINTS.
Several formula and methods have been published from time to time, the object of which is to change the colour of the platinotype print by subsequent staining or toning, and whilst by such methods pleasing colours may sometimes be obtained, they possess an element of uncertainty, and must not be too much relied upon. An exception in this respect must, however, be made in the case of what is known as Packham's method, the effect of which is to change the black platinotype to a sepia brown, or a brown slightly tinged with green. The necessary "tinctorial powder" must be obtained from Mr. Packham or through a dealer. To prepare the bath a packet of this powder is dissolved by boiling for three or four minutes in five fluid ounces of water, to which when cold add one ounce methylated spirit. This forms the stock solution and will keep for a long time if well corked. For use add thirty or forty minims of the stock solution to one pint of water, and in this steep the prints, turning them over frequently. Toning may occupy several hours. To expedite matters, the dilute solution should be made with water of 150° F., and the bath maintained at this temperature as in the case of hot-bath development. As soon as the desired tint is secured, remove the prints and wash well in three changes of cold water.
Prints may be so treated at any time after they have been made.
Glycerine developed prints are not suitable. Prints must have been very thoroughly washed, so as to free them from every trace of acid, also thoroughly fixed in acid if they are to be "toned" by Packham's method. If after "toning" and washing the whites of the print appear to have suffered, the prints should be placed for five or ten minutes in the following bath, which should be kept at a temperature of 180° F.
| Castille soap | 40 | grains. |
| Bicarbonate of soda | 80 | grains. |
| Water, hot (180° F.) | 1 | pint. |
This will clear the whites and intensify the colour generally.