A method of photolithographic color printing worked out and operated successfully by the firm of Orell Füssly, of Zürich, which started using it for monochrome work ca. 1886 and patented it in 1898. It is believed to have been a process of printing a light-sensitive asphaltum or bitumen film on stone under a continuous tone negative, and treating it in such a way that a fine grain image was formed. Very large editions of town views were made by this process, which can be classified as a form of screenless lithography. The process was later adapted to offset lithography and produced excellent screenless color lithographs in various art books published between the WW I and ca. WW II. See PHOTOCHROM-OFFSET.

Large size photochroms, as opposed to the cheaper postcards printed by the same process, have almost the appearance of natural color photographs, although under a magnifying glass they will show a delicate grain pattern. There is also a characteristic caption in gold lettering along the base of the print, with a serial number and “P.Z.” for Photochrom, Zürich.

Similar processes include the FREY process and variants by Wetzel & Naumann, Müller & Trüb, Schulz, etc. (Nadeau, Encyclopedia, p. xxx.).

Photochrom, ca. 1905. 167x224 mm Photochrom, ca. 1905. 167 x 224 mm

Photochrom, ca. 1905. 167 x 224 mm.