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.
Keeping Large Prints In Contact. Much trouble is often caused in printing from large negatives by the paper cockling and throwing the print out of contact. This can be overcome by using a pad of common white oilcloth on the print. Place the oilcloth with the finished side down. It may be necessary to use a felt pad on top of the oilcloth. Another way is to thoroughly warm the pad before putting it on the print, thus keeping the paper dry. If you should find a spot not printing in contact, rub the glass side of the negative over the spot with the finger or palm of the hand until the glass is warm, and it will draw the paper in contact at once.
Weak Prints. Weak looking prints very often come from failure to print dark enough. Make three prints, one as you think it should be, or as you have been printing, the second a shade darker and the third still darker. Tone them, select the best and use it as a guide. Weak prints are also caused by printing in an extremely cold room, or from chilled negatives. The use of extremely cold water will also cause weak prints. Either of these causes will chill the paper, and produce weak tones.
Properly Preparing The Gold Toning Bath. Difficulty will be experienced in making the gold bath test properly, if the litmus paper (both red and blue) is old, or of poor quality. All chemicals employed should be fresh and of the best grade. Be sure that the various stock solutions are made up in accordance with the formula. Never add borax until you have ascertained the condition of the gold bath, by testing with red litmus paper. If the bath is not alkaline in its action, i. e., if it does not change the red litmus paper blue, add borax quite cautiously.
Prints Toning Too Slow In The Gold Bath. If the prints tone too slow in the gold bath, it is either because you are not using sufficient gold, or the prints have not been thoroughly washed to eliminate the preservative and excess of free silver. Strengthen your gold bath by adding a little more gold, which has been previously neutralized, being careful that your preliminary washings are thorough.
Prints Toning Too Fast In The Gold Bath. If the prints tone too fast in the gold bath it is because the bath is too strong. Reduce strength by adding water. Add a little at a time until the prints tone at the proper speed. If the prints show bleaching in the whites before the shadows are toned far enough, it is because the bath is not sufficiently alkaline. Add more alkali. If the gold bath is acid it bleaches out the detail in the highlights. The whites are made to take on a pinkish shade and the shadows become weak and tone slowly.
Uneven Tones. This is generally caused by not using enough water directly after toning in the gold bath. In transferring prints from the gold bath they carry a certain amount of gold into the wash water, and unless there is plenty of water they will continue to tone in patches. Use plenty of water, and if the batch of prints is large, or the tray small, change the water frequently.