Snap Shot

An instantaneous exposure, owing to the shortness of which it is necessary to use a shutter of some description.

Snow Photography

The greatest difficulty in making snow scenes is the danger of flat results. Usually this is due to over-exposure. One must bear in mind that everything is very brilliantly illuminated, and when the ground is covered with snow there is very little opportunity of securing shadows which would tend to give contrast. For this reason the greatest of care must be exercised in exposure, as well as in development of the negative.

Castile Soap

Made from soda and olive oil. Only the pure white soap should be used for lubricating prints before burnishing. Castile soap is sometimes given a marble appearance by veining it with oxide of iron, which gives green or red lines, according to the age of the soap.

Soda

(See Sodium.)

Common washing soda is an impure form of carbonate of soda.

Sodium

Na.

Light, soft, ductile, malleable metal. Silvery-white when freshly cut, but rapidly becomes dull on exposure to air, and becomes covered with crusts of sodium hydroxide and sodium carbonate. Use. When in combination with carbonates, sulphates, etc., it fills an important place in the list of photographic chemicals.

Sodium Acetate

NaC2H3O2 + 3H2O.

Colorless, transparent crystals; efflorescent in warm air. Soluble in 1 part of water, in 2/3 part of cold, and in I part of boiling, alcohol. Used in gold toning baths.

Sodium Biborate

(See Sodium Borate.)

Sodium Bicarbonate

NaHCO3 - IV, 187.

White, opaque powder, or crystalline lumps. Cooling, mildly alkaline taste. Soluble in 12 parts of water, but insoluble in alcohol. The solution is slightly alkaline to litmus paper. Used principally in toning baths.

Sodium Bichromate

Na2Cr2O7 + H2O. Sodium Dichromate. , Red, deliquescent crystal fragments. Soluble in water. Often used in place of potassium bichromate, being much cheaper and more readily soluble than the potassium salts.

Sodium Borate

Na2B4O7 + 10H2O - IV. Borax. Hard, white crystals, or white powder; sweetish, alkaline taste. Soluble in I part glycerin, 0.5 parts boiling water; insoluble in alcohol. Used in various toning baths for printing-out papers in which it exercises an alkaline action.

Sodium Bromide

NaBr

White, crystalline powder; saline, feeble, bitter taste, absorbs moisture from air without being deliquescent. Soluble in about 1.7 parts water; 12.5 parts alcohol; 0.8 parts boiling water; 11 parts boiling alcohol. Used largely in gelatin emulsions, causing them to become more sensitive to the orange and yellow rays of light than does potassium or ammonium bromide.

Sodium Carbonate Crystals

Na2CO3 + 10H2O

Colorless, transparent crystals. Efflorescent in air. Strongly alkaline taste. Soluble in 1.6 parts cold water, 0.2 parts boiling water. The crystals contain about ten parts of water to one part of the chemical. For this reason it is more advisable to make these solutions by means of hydrometer test than by weight. Used largely as the accelerator in developing solutions. Its strong alkaline action readily opens the pores of the emulsion, thus permitting the developing agent to act more readily upon the latent silver image. For photographic use, only the purest form is recommended. Common washing soda is many times substituted for sodium carbonate, but uniform results cannot be relied upon when washing soda is employed.