CATATYPE (Fr. and Ger., Catatypie) A process depending on catalytic action, which is defined in the preceding article. In the original catatype process patented by Messrs. Ostwald & Gros in i9oi, a negative image consisting either of silver or platinum is immersed in a solution of hydrogen peroxide in ether, being then withdrawn and the ether permitted to evaporate. The peroxide is decomposed where ever it comes in contact with the metal, but in various degrees according to the different grada tions of the picture. The negative so treated is now pressed into contact with a gelatine film for a few seconds, an invisible hydrogen peroxide image being thereby taken up by the latter. If the gelatine film is then immersed in an alkaline solution of a manganous salt, brown manganese peroxide is formed wherever hydrogen peroxide is present, a brown positive image being thus obtained. Or, if an alkaline silver
solution is used instead of a manganous salt, a black image in metallic silver results.
Another method is to place an ordinary negative in contact with hydrogen peroxide, as before, and to bring it for about thirty seconds into contact with a gelatine paper in which a pigment is incorporated, the paper being then immersed in a solution of a ferrous salt. The invisible hydrogen peroxide image taken up by the gelatine will oxidise the ferrous salt to the ferric state, in which it is able to render the gelatine insoluble, the insolubilisation exactly corresponding to the various degrees in which the peroxide is present. The print can then be developed with warm water, as in the carbon process. There are many other variations of the catatype process, mostly patented.