This section is from the book "Complete Self-Instructing Library Of Practical Photography", by J. B. Schriever. Also available from Amazon: Complete Self-Instructing Library Of Practical Photography.
276. In the double transfer process there is little gained over the single transfer, as far as results are concerned. If anything, better results are obtained by the single transfer. The main object of the double transfer is to obtain unreversed prints. This process is more complicated, and it is recommended only in cases where the reversed image will not answer; for instance, in street scenes, landscapes and architectural pictures where the original positions should be preserved, and when you are printing from ordinary negatives. If special reversed negatives are made, the double transfer is unnecessary.
277. When printing from portrait negatives the change of the picture from right to left is of no consequence. We advise using the single transfer for portraiture, and the double transfer for only such work that must be photographed as the original appeared. The only change in the manipulation of the double over the single transfer is in an additional transfer from the second support, which is temporary instead of permanent, to a third or final support. Instead of using a permanent support in the single transfer, one on which the carbon becomes permanently attached, you use what is termed a temporary support. This support being used only to develop the image upon the surface, instead of being prepared with a tacky substance which holds the tissue or film fast, is prepared with a waxing solution, from which the image can be transferred to a final permanent support, prepared with a tacky substance.
278. The double transfer can be effected in two different ways: First, by using a flexible temporary support of paper, and second, by using plain ground-glass or opal. The flexible support may be obtained already prepared from the dealer, cut in regular size sheets, or the paper can be bought in full size sheets 18 x 23 inches and prepared by yourself. This support can be used several times, provided that it is thoroughly dried and waxed after each operation.
279. The waxing solution is prepared as follows:
280. There are two methods that may be employed for waxing or preparing the support: First, by floating the support on a bath of waxing solution; second, by applying the wax with a soft flannel pad. This latter method is preferred, as it is more simple and requires less of the solution. When applying with the pad, first tack the flexible support by the four corners on some smooth surface board and rub it with the flannel pad moistened with the waxing solution. The rubbing must be done lightly and evenly, so as to effect a polish such as the paper had before applying waxing solution. Remove all lint, if any, from the surface before waxing is dry, as the support must be perfectly clean before the transfer is made.
281. The operation of this first (temporary) transfer and the development is identical with that of the single transfer process described in the previous chapter.
282. After having prepared your flexible support, as directed above, immerse it for a few minutes in a tray of cold water. At the same time immerse your carbon print in the same water. You can either place the flexible print under the carbon and bring the two in contact while in this cold water, and then withdraw from the water and lay on the squeegee plate, or you may lay your flexible print on your squeegee plate, waxed side up, and then place the print on it face down. The method of bringing print and support in contact underneath the water is preferable, as there is less liability of air-bells or bubbles gathering between the carbon and transfer. Now, cover with the rubber cloth and squeegee into contact.
283. After the print and transfer are in contact, lay a dry blotter over the print and mop off all moisture, as the least drop of water will cause spots and the spots will cause blisters after the transfer is made. After thorough mopping, the prints are hung up to dry for say 15 or 20 minutes, when they are then ready for developing, which is done exactly the same as in the single transfer process. After the carbon is fully developed it is placed in the alum or hardening bath for 12 minutes, and then washed for half an hour, when it is ready to be transferred to the final support.
284. It is better to use powdered (potash) alum, which must be thoroughly dissolved before using, for the least undissolved particles coming in contact with the film will not only stain but scratch it. In order to prevent any undissolved particles in the bath, filter before using. This bath must be cold-never warm.