The Dictionary Of Photography

A True Historic Record Of The Art & Practice Of Photography 100 Years Ago.

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Caseine
Celluloid
many times. Roll a sheet of pasted paper round a rod so as to form a tube, and when dry cut to suitable lengths and close with a cork at each end.
Caseine. The constituent of milk which, when coagulated, produces cheese. Skim cheese dissolved in weak ammonia yields a preparation which will coat paper like albumen, and in its relation to silver salts caseine is similar to albumen; but it is not much used in modern photography.
Castile Soap. A soap made from soda and olive oil, and used as a lubricant for burnishing. Castile soap is sometimes veined or marbled by the addition of sulphate of iron, and when freshly prepared is yellowish white, with bluish-green streaks. When old the iron salt turns red by oxidation. The white Castile soap is to be preferred.
Catalysotype. An old process invented by Dr. Wood, in which paper was impregnated with syrup of iodide of iron, and then painted with a solution of nitrate of silver. It ,was then exposed in the camera and the image gradually appeared, appar-ently by the action of moisture in the air. Sometimes the image was developed by the use of water. This method appears to be the foundation of certain modern processes in which iron and silver are used in conjunction, and water intensifies or tones the faint image.
Cathography. Synonymous with Radiography (q.v.).
Caustic. A term applied to corrosive or irritant chemicals. Thus nitrate of silver is known as lunar caustic, and the caustic alkalies are the hydrates of the alkaline metals. In optics the term caustic (burning line or burning curve) is applied to lines or curves where crossing rays illuminate a surface with double intensity. The bright curved line often seen on the bottom of a cylindrical earthenware mug (or better if such" a vessel is filled to within an inch of the top with milk) is a good illustration. See Brewster's "optics," 1831 ed., p. 60 to 65. On p. 64 two experi-ments are described, in which caustics serve very well to illustrate the nature of spherical aberration.
Celluloid. A compact transparent material, the chief con-stituent of which is pyroxyline or dinitro-cellulose; camphor
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