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.
Parts Of The Film Leave The Plate. This is a certain sign that the collodion has not been sufficiently set before sensitizing, or if the collodion has been well set before sensitizing and the film still leaves the plate, try albumenizing the plate before flowing with the collodion. Be sure this albumen is thoroughly dry before you apply the collodion.
Parts Of The Film Of The Plate Thicker Than Others. This is a certain sign that the plate was not evenly flowed with collodion. Some portions may have been double-coated by tipping the plate so as to allow the collodion to flow back over the portions which were formerly coated.
Parts Of The Plate Apparently Not In Contact. This would indicate that the plate was not thoroughly cleansed. Particles of old film may have been allowed to remain upon the plate. Where mercury was used for intensifying the old plate which you have washed and again used, unless the mercury is entirely eliminated in the washing this same trouble would appear. Nitric acid is the only chemical that will entirely eliminate these defects. To be absolutely certain of overcoming such defects the plate may be albumenized before collodionizing it, according to instructions given in the lesson. Dampness of the plate will give the effect of lack of contrast. Always examine the plate carefully before collodionizing and see that it is perfectly dry.
Ridges In The Emulsion. This is generally caused from a collodion that is prepared too thick, but it may also be caused from a piece of bad glass with chipped edges, which will many times cause the collodion to clog and not sweep cleanly over the plate, resulting in furrows in the emulsion. The only remedy for the latter is not to use such plates. See that all glass has clear edges and is free from defects generally.
Part Of The Plate Thinner Coated Than Others. This may be caused from using too thin a collodion; the upper portion of the plate being flowed first would then not receive as heavy a coating as the lower portion. It may also be due to an excess amount of alcohol, causing the plate to dry too rapidly, and as it would naturally dry more rapidly at the top than at the bottom, it would give an uneven coating.
Fine Net Work Markings Over The Film. This may be caused from too much bromide of cadmium or lack of sufficient alkali. Perhaps more ammonium iodide would rectify the defect.
Weak Image In The Negative. This is probably due to lack of sufficient gun-cotton; the use of old gun-cotton will also produce this result.
Straight Lines Across Plate After Sensitizing. This is evidently due to improper immersion in the silver bath. The plate was not lowered in the bath with one sweep, but, on the contrary, you halted for a second, when only a portion of the plate was immersed.