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.
To Clean A Lens. First spread upon a table a clean sheet of paper; take your lens carefully apart; now dust with camel's-hair brush each lens on both sides; then take a clean graduate, pour in two ounces of distilled water, one ounce of alcohol and three drops of nitric acid (C. P.), mix well, and with a tuft of filtering cotton dipped in this solution, rub the lens on both sides; polish with a clean chamois which is kept for this purpose only, which, when not in use, put away in a clean paper bag. After the lenses are all polished, before putting together, wipe out carefully the brass tube; then dust each lens with a camel's-hair brush (never blow on them) and put together. A lens cleaned in this way will keep clean much longer than it would if simply wiped with a chamois.
755. Large round spots, but less numerous, are caused by bubbles in the developer, often due to water containing vegetable matter. Melted ice, distilled or well water should be used if possible. Angular spots are due to dust on the plate at the time of exposure. Plates should be dusted with a camel's hair brush before development and the plate holder and camera kept scrupulously clean. The dusting may electrify the plate if done too vigorously.
756. Triangular Transparent Spots are caused by using a developer on which a scum has formed. It should not be used without filtering. The scum forms rapidly if the room is warm and the water used contains organic matter.
757. Opaque Spots and Lines are caused by allowing pyro, hypo or sal soda to get on the dusting brush. The dark room should be kept absolutely clean, any spilled hypo or other solutions should be wiped up immediately, for after drying the dust of chemicals will float about in the air and cause endless trouble.
758. Small Opaque Spots may also be due to the presence of iron in the water. To avoid same a canton flannel bag should be so tied over the faucet that the water filters through it. The spots may be removed by diluted sulphuric or muriatic acid.
759. Blurred Opaque Finger Marks or Spots are caused by placing plates face to back after exposure. Plates left in such contact any length of time will transfer any markings from the back of one plate to the sensitive surface of another. Always put plates away face to face after exposure.
760. Granularity of Negative - This is usually a warm weather trouble. The developer should not be too strong in alkalinity or too warm. Fix well in a strong, fresh, acid alum bath. Dry in a current of air.
761. The Making up of Developer Solutions - If distilled water only were used in making solutions of developer, half the troubles of development would be avoided. If river water is taken, it should be boiled, cooled and filtered before mixing, as it generally contains much vegetable and other organic matter. Well water that is free from iron and sulphur, and not too alkaline, may be used without boiling. Melted ice is good, but should be filtered.
762. The Developer should be made up with reliable chemicals to an established formula strictly according to instructions. When a convenient way of making up the solution has been fixed upon, those particular weights and measures should be used thereafter. This procedure should be so much a habit, and the confidence in the materials used (this includes the water) should be so based upon past experience or the guarantee of reliable people, that the developer should be the last place to look for trouble. A great many troubles laid at the door of the developer, are the result of mistakes in exposure and lighting. The worker should be sure that his lighting ought to give him the desired contrasts and that his exposures are sufficient and not too great, before blaming the developer.