An improved version of the ozobrome process patented by Thomas Manly (d. 1932) in 1905. Manly's process produced a carbon print from a bromide print. Pigmented gelatin paper (carbon tissue) was sensitized with bromide and ferricyanide compounds, contacted with a silver bromide print to harden the gelatin, and developed as a carbon print. Ozobrome had a number of advantages over traditional carbon printing: it required neither an enlarged negative nor daylight printing, the final image was not reversed, and the bromide print could be redeveloped and reused. Ready-made materials were produced by the Autotype Company and licensed to Kodak in the USA. The ‘carbro’ process—a conflation of ‘carbon’ and ‘bromide’—was launched by Autotype in 1919. A silver halide print was bleached with a dichromate solution in contact with the pigmented gelatin paper, producing a result similar to that of the original carbon process without exposure to light.
A colour process called Trichrome Carbro used prints from red, green, and blue separation negatives to make gelatins in cyan, magenta, and yellow pigment, which were stripped and assembled in register on a final transfer paper base. It was a difficult process, and was superseded by dye transfer.
A particularly attractive property of carbro (and carbon) prints was the variation in surface texture from matt highlights to glossy shadows (unfortunately lost in reproduction). In high-contrast prints the darker areas actually appear in low relief.
— Graham Saxby/Hope Kingsley
See also ozotype.
