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.
Transferring The Print. Into a tray of clear, cold water place as many sheets of celluloid as there are carbon sheets to be developed. In another tray of clear, cold water place the carbon tissue to soak. This operation should take place in subdued light-electric or gaslight is good. Daylight can be employed when the curtains are drawn on the windows so as not to admit any strong light on the print, as the tissue is much more sensitive to light than ordinary printing-out paper. When placing your carbon tissue in the tray of cold water it will curl up at first, with the black side inward. You must keep it agitated, and with your camel's-hair brush remove the air-bells from the back of the print as well as the face. Allow this tissue to remain in the tray until it flattens out. This will require about three to five minutes. Next, turn the black side down and immediately take your transfer paper or celluloid and slide it into the tray underneath your carbon tissue, having both under the water, and then carefully and steadily draw the carbon onto the support. Be sure that both are tender the water when this is done, otherwise the surface of the print, which is very sensitive, will be marred.
156. As soon as the carbon tissue is properly located on the celluloid, lift both together from the tray, by holding at one end with the first finger and thumb of each hand, and place the print, celluloid side down, upon your glass squeegee plate. Cover the print over with the rubber cloth; then with the flat squeegee thoroughly expel all water or air-bells that may be between the celluloid and the carbon, thus bringing the carbon and support into perfect contact. Sometimes a roller squeegee will help you to expel these air-bells better and give you better contact, but it is well first to mop off the surplus water with a flat squeegee, then roll over gently with the roller squeegee. All air-bells must be eliminated, so the squeegeeing must be very thorough. After squeegeeing, place the print between dry blotters on a table or some level surface, then weight it down with a sheet of heavy plate-glass or ordinary glass with some light weight upon it. Allow the prints to remain under weight for at least fifteen minutes.
Beginning Of Development. After fifteen minutes have elapsed, the print on the transfer paper is placed in the developing tray, or in other words, the hot water bath of 80° Fahr. The print should not be bent or twisted during this process, or the tissue may be separated from the transfer paper around its edges. That is a difficulty to be avoided as much as possible. The water in the dish should be comfortably warm, about 80° Fahr. It is advisable to have a suitable thermometer in order to correctly gauge the temperature. After some experience with the printing and developing of carbon paper, it will not be necessary for you to use any other guide than your fingers. If you cannot bear your hands in the water, it is too hot, while if it does not feel decidedly warm, it is too cold. It is also very important, when changing the temperature to a higher one, to make the change gradual, rather than subject the print to sudden changes of temperature.
158. Into the first water, the temperature of which is approximately 80 degrees, slide the print, with the celluloid side down. If it tends to float to the top, push it gently down with the fingers. If air-bells appear on the surface remove them with the camel's-hair brush. After a lapse of half a minute or so in the warm water the black coating will begin to dissolve and will ooze out at the edges of the print. This stage should on no account be hurried. No harm will result if the print is left untouched from two to five minutes after the pigment is seen to be coming out of the edges, and, indeed, anyone not familiar with the process will find less likelihood of failure if the tissue is allowed to remain for five to eight minutes in the warm water before commencing to strip. If the black pigment does not ooze out of the sides in a few minutes, catch the edge of the print between the thumb and first finger and gently shake it in the water. This will start the black pigment dissolving.