carbon process

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A photographic printing process using permanent pigments, such as carbon, contained in a sensitized tissue or film of gelatin.

Wiktionary

1. n. the process of making carbon prints

GNU Webster's 1913

1. (Photog.) A printing process depending on the effect of light on bichromatized gelatin. Paper coated with a mixture of the gelatin and a pigment is called carbon paper or carbon tissue. This is exposed under a negative and the film is transferred from the paper to some other support and developed by washing (the unexposed portions being dissolved away). If the process stops here it is called single transfer; if the image is afterward transferred in order to give an unreversed print, the method is called double transfer.

WordNet 3.0

1. n. a process of printing on paper coated with bichromated gelatin containing pigment