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.
Print Flat Or Sunken In Appearance. Paper insufficiently or unevenly sized. The paper should be kept in the sizing and salting bath not less than two minutes. If the salting bath is applied to the surface of the paper with a swab of cotton flannel, great care must be taken that the solution is evenly distributed; otherwise irregular streaks will show in the print.
Paper Curling When Floating On Salting Bath. Caused by paper being too dry. It should be well dampened before salting.
Paper Darkening While Still Fresh And Before Use. Lack of citric acid in the sensitizing bath.
Print Appears Weak After Fixing. Insufficient exposure. The paper must be considerably over-exposed, as the image weakens considerably in the fixing bath. Too strong a fixing bath will also cause the prints to bleach.