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.
Temperature Of The Water. The temperature of the water has much to do with the curling of the paper. In water too cold prints will curl readily. The proper temperature is about 65 or 70 degrees. During warm weather it is safe to use the water at regular tap temperature. In cold weather the chill should be taken off by adding warm water.
170. Another method of flattening, which has been recommended for large prints especially, and one we have found to work very satisfactorily, is as follows: Use two trays. One tray, after careful rinsing and while still wet, stand on end, filling the other tray one-third full of water. Immerse the prints in the water in the regular way and transfer them, face down, to the bottom of the tray standing on edge, being careful to flatten out each print. This keeps the prints in a perfectly flat condition. Splash a little water over them occasionally and allow to stand for five minutes, after which they will lay perfectly flat and can be washed in the usual manner.
Trays. Poor trays are really expensive things to have, as they cause loss of many dollars worth of time and stock. For that reason, good clean trays, free from iron rust, should always be employed. Rubber trays give the best all-around service. An inexpensive tray can be constructed by simply making a box of wood and covering it with heavy oilcloth. As the oilcloth becomes worn replace it with new covering. All trays should be thoroughly cleansed, before using, by scouring with bicarbonate of soda, or common salt which has been moistened, finally rinsing well in clean water.
172. The gold bath trays should not be used for the platinum bath, nor should the tray used for washing prints after the hypo be used for washing prints before the gold bath. Never allow the hypo tray to come in contact with the other trays but keep it at some distance from them.
Toning In The Gold Bath. Taking for granted that the toning bath has been prepared according to the previous instruction, it is necessary to test it and ascertain whether or not it is perfectly balanced and in proper condition to give the best results.
174. Place a print in the toning solution, and spray the solution over the print with the right hand, watching it carefully. If the highlights and shadows tone equally, you will know your bath is working properly. Should the highlights tone chalky, bleaching - eating away as it were - and the shadows refuse to tone, this at once indicates that the bath is still too acid, and it is therefore necessary to add a few drops of borax to it. A fresh print should be placed in the bath, and if the bleaching continues, add a few more drops of borax. Continue adding, very cautiously however, until bleaching ceases and the test print tones down to a rich purple. The borax being a strong alkali must be added very carefully, or muddy whites will be the result.
175. Should the print tone this far and appear good and clear in the whites - not bleached nor muddy - your bath is at the right stage and you can proceed with the rest of the prints. It is advisable to always judge the prints by looking through them to the light. In this way you can judge more correctly when they are fully toned. Tone down to rich purple, and have bath strong enough to do this in about six to eight minutes. After toning place the prints into a tray of clear water until all are toned.
176. If your test prints show that the bath is toning too fast add more water, which will reduce the speed. On the contrary, should you find that the bath is working slow, add a little more gold. The gold, however, should always be neutralized before adding to the bath. To do this pour the gold into a graduate and add sufficient alkali until it turns red litmus paper blue. If you add gold, which is acid, to the bath without neutralizing, it may throw it out of balance. Sometimes it causes the bath to bleach, or produces pink whites in the platinum bath. Where large batches are being toned the bath will become worked out before all the prints are carried through. When the prints lag in the toning bath and do not tone in a reasonable time, fresh neutralized gold must be added to keep the bath working at a certain speed.
177. Proceed with the toning in exactly the same manner as with glossy paper; the only attention the bath will need is to keep it properly balanced. Never have more prints in the bath than you can readily handle. They should never be allowed to lay in the bath but must be picked over and over, or uneven tones will result.