Sodium Sulphite

Dried - Na2SO3.

A white powder containing from 85 to 90 percent of sodium sulphite. The best form of sodium sulphite to use, as it works better and its purity is more certain than the crystalline form.

Sodium Thiosulphate

(See Sodium Hyposulphite.)

Sodium Tungstate

Na2WO4 + 2H2O.

Colorless prisms or rhombic plates. Soluble in four parts of water. Solution is alkaline to litmus paper. Used principally in toning baths.

Soft Effects

The opposite to contrast. Harsh, contrasty results are seldom desired in the photographic print, and it is for this reason that the photographer usually aims towards securing soft effects. One should not go to the extreme, however, as flatness and a picture lacking life would result. It is necessary to have high-lights and shadows, but the intervening tones should all be well represented, for it is the half-tones that give contrast to the picture. The individuality of the photographer and his own likes and dislikes will have much to do with his individual idea of what is meant by soft effects.

Solar Camera

(See Camera, Solar.)


(See Reversal.) Also a term applied to the bronzing of prints. Solidification.

The changing of a liquid substance to the solid state. Solution

The changing of a substance from a solid or gaseous state to the liquid state. In photography, however, the term solution is used when a substance is dissolved in water.

Clearing Solution

A solution having a weak dissolving action upon metallic silver. Generally composed of citric acid and alum. Used for clearing negatives which become stained during development; also for papers.

Concentrated Solutions

A liquid in which is dissolved a large amount of a substance. The object of such a solution is usually to decrease the amount of solvents, having as much of the dissolved substance as possible.

India Rubber Solution

Made by dissolving the purest rubber in benzole, carbon di-sulphide, etc. Often used around the edges of plates, to prevent frilling; also as a substratum coating for collodion and albumen processes.

Saturated Solution

A solution is said to be saturated when it will hold no more of a solid. To obtain a saturated solution of any solid, it is advisable to dissolve the chemical in warm water until some of the solid remains at the bottom. Upon cooling some of the chemical which was in solution will be thrown down precipitated. The solution will now be a saturated one. As a rule, warm water will dissolve and hold in suspension a greater quantity of a solid than cold water. Saturated solutions for use should have a temperature of 6o° Fahr., or 15o Cent.

Stock Solution

A concentrated solution for either developing, toning, fixing, etc., baths. Stock solutions are to be diluted with water before use.