The Dictionary Of Photography

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

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Cellulose                                        Changing Boxes and Bags
being the usual medium (or quasi solvent) for agglutination. Celluloid dissolved in amyl acetate, acetone, or other suitable solvent, forms a useful varnish. (For a method of repairing articles of celluloid, see note under Acetone. See also Cellulose.)
Cellulose. A general term applied to the fibrous or hard constituent of plants. It contains C6H10O5, and is the basis of the various kinds of paper, linen, and cotton. Treated with nitric acid, or mixtures of this acid with sulphuric acid, it yields a more or less completely nitrated product; that in which two of hydrogen are replaced by the group N02 being the soluble pyroxyline used in making collodion and celluloid. The acetic and other derivatives of cellulose have been suggested for the making of transparent and flexible films to replace ordinary Celluloid (q.v.).
Centigrade. See Thermometer.
Centigram, Centimetre. See Weighing and Measuring.
Centrifugal Separation. Plener, by rapidly rotating a metal vessel silvered inside, and containing gelatino-bromide emulsion, succeeded in separating the sensitive constituent which adhered as a cheese-like mass to the inner circumference of the vessel. It could then be stirred up with water and be again separated, and so washed any number of times, after which it could be incorporated with fresh gelatine. This method has since been largely employed as a means of getting rid of decomposed gelatine, which may cause frilling, or fog.
Ceramic Photography. See Enamel and Ceramic Photo-graphy.
Changing Boxes and Bags. The changing bag is a very portable form of the dark tent (see Dark Tent), and devices of this kind are occasionally used for changing plates when out of doors. Generally speaking the changing bag is made of opaque material with arm holes, and if in box form it may be called a changing box. Various mechanical devices for transfer-ring plates from the dark slide to a store box, and vice versd, are also called changing boxes, but they are not much used at the