Of developers I cannot say very much, except to stronghly recommend adding glycerin instead of alcohol, or using half alcohol and glycerin when the bath is greasy. Glycerin gives such a command over the development, allows for such deliberation of treatment, and has all the exquisite flowing qualities of gelatin, without the retarding effect on exposure, that once an operator gets used to its easy manipulation he will never go hack to the simply alcoholic developer. For indoor working, I use fifteen grains of protosulphate of iron to one ounce of water, and for outdoor work from five to ten grains. Acetic acid is added according to time of year, kind of subject, and quality of light. - Alfred Hughes.
That indicates that the developer has been too strong, and without sufficient acid in it; that it was also carelessly applied,- instead of flowing it over evenly, it was thrown over with a dash, causing the spot in question. The danger of spoiling your negative is not over when exposure is made. Many troubles arise with the developer. When the iron is too strong, and without sufficient acid to restrain its action, it causes an unequal reduction of the silver, which produces the ugly markings just now mentioned.
177. And there are still more kinds of defects constantly occurring to mar the peace of the working photographer. They are, as a general thing, however, resultant from heedless manipulation, and may be avoided if the proper care be taken, and your purchases are made from a reliable dealer, whose prices are fair enough to keep him from the practice of adulteration. While chemicals are exceedingly obstreperous, they can be kept in comparatively good order if they are given the attention laid down in the rules. Knowing the causes of defects, then, it should not be difficult to avoid them.