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.
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.
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.
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.
NaC2H3O2 + 3H2O.
(See Sodium Borate.)
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.
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.
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.
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.
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.