Kallitype and Vandyke Brown Print Processes
By: Robert Hirsch
Dr. W. W. J. Nichol invented the kallitype in 1899. The process is based on Sir John Herschel's iron-silver reduction process called the chrysotype (the modern process is provided at the end of this section). This process is similar to platinum printing, except the kallitype image is made up of metallic silver instead of platinum. The kallitype is a simple process consisting of silver nitrate and ferric salt. When the kallitype emulsion is exposed to light, some of the ferric salt is reduced to a ferrous state. The newly created ferrous salt reduces the silver nitrate to metallic silver. This metallic silver is not as stable as metallic platinum. Careful processing that removes all the ferric salt and nonimage silver greatly increases print stability.
The kallitype process was never commercially popular because it was introduced at the same time as gaslight papers, which were contact-printing, developing-out papers with a silver chloride emulsion that could be exposed by artificial light. Even more important, the kallitype had an initial reputation for impermanence. When Nichol first unveiled his process, he recommended the use of ammonia for a fix, which proved to be ineffective. However, when fixed in hypo, a kallitype can be as permanent as any other silver-based process.