Caustic Potash

(See Potassium Hydroxide.)

Caustic Soda


Pure gun cotton with some solvent. Prepared by Schering for making collodion. As celloidin is of very uniform texture and all impurities have been eliminated, it is preferred to gun cotton for making collodion.


A transparent, flexible, or horny substance, very inflammable. Used as a support for films; as imitation ivory for miniatures; and, when dissolved, as a varnish.

To Mount on Celluloid

Schering's Celloidin..........................

1 drm.

Amyl Acetate.....................................

2 ozs.

Float the print on this solution, also apply the solution to the celluloid, then squeegee the two together.

Celluloid Varnish. (See Varnish.)



Pure cellulose is manufactured by boiling linen and cotton fibre with diluted potassium caustic. The cellulose is extracted with alcohol and ether. A mixture of nitric and sulphuric acids converts it into gun cotton, which latter is used in making collodion.

Celor Lens

(See Lens Celor.)


The one-hundredth part of a gramme - a measure of weight used in the Metric system.

Centilitre, or Centiliter

The one-hundredth part of a litre - a Metric measure of capacity or volume.

Centimetre, or Centimeter

The one-hundredth part of a meter - a Metric measure of length.


(See Calcium Carbonate.)

French Chalk

Steatite or Soapstone. Powdered French chalk is used for lubricating woodwork. Also to prevent gelatin or similar substances adhering to glass.


Excessive contrast in negatives or prints the high-lights of the print being pure white.

Changing Bag

A light-tight cloth bag used for changing plates, loading plate-holders, etc.

Changing Box

(a) A box for holding exposed plates, (b) A box which may be attached to the camera for unloading and refilling plate-holders.

Chemical Action of Light

(See Light, Chemical Action of.)

Chemical Focus

(See Focus, Chemical.)

Chemical Fog

(See Fog, Chemical.)


Chemistry is the study of chemicals, their origin, combinations, properties, etc., and takes into consideration solids, liquids and gases. (Also, see Qualitative and Quantitative Analysis.)

Inorganic Chemistry

The chemistry which treats of metal bodies.

Organic Chemistry

Generally speaking, the chemistry which treats of bodies which are not metals.


An art term denoting correct arrangement and proportion of light and shade in a picture.