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.
Enlargement Sharp In The Center But Out Of Focus At The Edges. Evidently your lens is not large enough to cover the plates to be enlarged and does not cut absolutely sharp to the edges unless a small stop is used. Use a smaller stop or diaphragm and the entire image will be perfectly sharp, provided the negative is sharp.
Green Tones. Green tones are caused by over-exposure or by using too much Bromide. Discard this bath and add your Bromide to the new bath cautiously. Use small pieces of paper to test it and add only enough Bromide to cause the whites to develop clear without showing any green.
Flat Prints. Flat prints will occur when you use too soft a paper on a fiat or soft negative. Making your enlargement from such a negative by daylight and stopping down the lens sufficiently would produce contrast.
Contrasty Prints. Caused by printing from a strong negative and using hard paper, or printing from a strong negative by artificial light. Give longer exposure and dodge while printing by covering up the portions that print rapidly, and allowing the extra exposure only on the parts which are strong.
Sharp Vignettes. Caused by not keeping the vignetter in motion. Work your vignetter to and fro, up and down, back and forth between the lens and enlarging easel.
Prints Refusing To Tone Sepia In The Hypo-Alum Bath. If this bath has been prepared properly you should have no trouble. This is extremely slow in toning, but you will find it will work better after a number of prints have been toned in the bath. A good plan is to cut up an old print and put it into the fresh bath when it is first made up. This will help to ripen the bath, give it age, and it will tone much more readily.
Difficulty In Judging Which Is The Sensitized Side Of The Paper. This difficulty you will readily overcome after a little practice. You will always be able to distinguish the face of the paper by its curling in, the convex side being always the back.
Enlargement Reversed From The Original Negative. Caused by placing the negative in the holder the wrong way. Always face the film side of negative toward the lens.
75S. Image Appearing Upside Down on the Enlarging Easel. - This is because you placed the negative right side up in your holder in the enlarging-camera. Place it into the holder upside down and it will appear right side up in your easel.
Hair Lines, Like Fine Pencil Marks, On Enamel Bromide Paper. These are abrasion marks and the lines generally appear rather prominently after development. If allowed to remain they would spoil an otherwise good picture. They are. however, easily removed, but from the dry print only, by gently rubbing with a tuft of cotton moistened with wood alcohol.
Small White Spots And Streaks On Matte-Enamel And Platinoid Papers. Caused by the developer not acting evenly when first flowed over the print. To overcome this, before pouring the developer over the print, take a camel's-hair brush, or a piece of cotton and brush over the entire print while it is immersed in the water.
Not Fixing Properly. You can tell when the prints are fixed by looking through them or upon the surface in a good strong light. The unfixed portions will be of a greenish-yellow tint. When thoroughly fixed they are clear and even throughout.