DEFECTS IN NEGATIVES, AND THE REMEDY.
The most common defect in negatives, and one which it is easy to avoid, is the small transparent spots which appear on the negative after developing and fixing. These spots are called pinholes, and are caused by small specks of dust which cling to the film, and which do not wash off when the developer is turned over the plate. When a print is made from a negative in which there are pinholes, small black spots appear in the finished print wherever there were pinholes in the film. These holes can be filled up by retouching, but they may be avoided altogether, and prevention is much better than cure. After the sensitive plate is in the holder, dust it over carefully with a small wad of surgeon's cotton before putting in the slide. If plates remain in the holder some time before they are used, it is a wise plan to dust them again before they are put into the developer. Pinholes are sometimes caused by using old developer which has not been filtered, and the tiny specks which are in the solution settle on the plate during development. Always filter developer after once using, and it saves time if it is filtered at once when through developing.
Larger spots with sharp dark edges are caused by air-bubbles forming on the plate when the developer is poured over it. If the tray is slanted a little when the solution is turned on the plate, air-bubbles are seldom formed. A piece of clean surgeon's cotton passed quickly over the plate will break the bubbles.
Where there are large irregular spots on the plate which are not fully developed, it shows that the developer did not cover all the plate immediately, and therefore acted longer on one part than on the other. There is no remedy for this; but such markings can be prevented by pouring the developer quickly over the plate and rocking the tray for a few seconds.
If the negative, after fixing, is covered with fine markings, the print looking as if the negative from which it was made was crackled, it shows that the tray was not rocked sufficiently during the process of development. The tray should be gently rocked in all directions, so that fresh developer is constantly passing over the sensitive film. (Not long ago one of the members of the club sent two prints to the editor, one of which was covered with fine markings. The letter stated that the negatives were made and developed one after the other; and while the first was all right, the second had the crackled appearance. An explanation of the cause was asked and received.)
If the negative after developing and fixing turns yellow it indicates that the plate was not left long enough in the fixing-bath. As explained in one of the papers on the chemistry of photography, when the negative is placed in the fixing-bath a new compound is formed of the unchanged chloride of silver and the hyposulphite of soda. They unite and form a double salts, called silver sodium hyposulphite or thisulphate. This double salt is soluble in a solution of hypo, and the fixing-bath must be strong enough not only to form this double salt, but also to dissolve it. When it is thoroughly dissolved it is quickly washed out of the film. If the fixing-bath is too weak, or if the plate is taken from the bath too soon, the plate will soon turn yellow, and in time the image will be destroyed. To prevent this the plate should be left in the fixing-bath for five minutes after the plate is cleared from the silver bromide.
When a negative after drying has a whitish appearance with a rough surface, it is because the plate was not washed long enough after removing from the hypo bath. Wash plates an hour in running water, or in eight or ten changes of water, changing at intervals of five minutes.
Arthur Nilsen asks if portraits can be made better with snap-shots than with time exposures; and if with time exposures, the length of the exposure. Snap-shots for portraits give too harsh contrasts. For a time exposure with good light simply taking off and replacing the cap quickly will be long enough; or if a hand-camera with drop shutter, open and close the shutter as rapidly as possible without making the exposure instantaneous. One must learn to regulate the exposure according to the light, and the rapidity of the lens and plate used. With a little careful practice one can learn to expose the plate correctly.
D. Saylor Wilson asks how to tell when a plate is fully developed. Examine the plate by looking through it toward the red light. If the detail is well out, and the negative looks as if it would be dense enough for a good print, return the negative to the developer, and rock it till the image is fading rapidly, then remove and wash and fix. With some kinds of developer the image must be allowed to fade entirely, but with hydrochinon developer the plate is developed far enough when the plate looks dense when examined by looking through it toward the light.
