Cal′o-type.
（Photography.) A process invented by Fox Talbot. Paper saturated with iodide of silver is exposed to light, and the latent image developed, and afterwards fixed by hyposulphite of soda. The paper is floated on a solution of iodide of potassium, dried, floated on a solution of nitrate of silver. The effect is a film of iodide of silver, by the double decomposition of the two salts in contact. Excess of salts is washed away, and the paper dried, in the dark. The sheet, before use, is floated on a solution of gallo-nitrate of silver. After exposure in the camera the latent image is developed by nitrate of silver and saturated solution of gallic acid; then fixed by bromide of potassium and hyposulphite of soda. The result is a negative, which by a repetition of the process produces a positive.
