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.
Practice Work. It is advisable to purposely under-time a few experimental plates under different conditions. The different methods suggested for the treatment of plates under-exposed should be tried one method at a time. The negatives of first experiments should be dried, and good solid proof prints made; the necessary data should be noted on back of proofs, including date, and stating whether first, second or third experiment. These proofs should then be filed for future reference, and further experiments made according to instructions, always being guided, of course, by results of former experiments. It will not require many tests of this kind before one becomes familiar with the appearance of plates in the developer of all exposures, and can judge instantly how much nursing they require to produce good negatives, and by instinct apply the proper method.