Print fading was a common occurrence in the earliest days of photography, and several people sought to address themselves to this problem. In the mid 1850s some began to experiment with carbon, and in 1864 Joseph Wilson Swan perfected the process, which he also patented.
Prints made using this process came in any colour, and were permanent. The sensitising solution consisted of a mixture of carbon, gelatin, the colouring material, and potassium bichromate. Once the paper was exposed to light, the areas exposed became insoluble in water. Development consisted of washing the unexposed soluble material away in warm water.
The image being laterally reversed, it needed to be transferred to another base which was usually paper, but which could be leather or wood; the image was in relief.
A variation on the carbon process was the Woodburytype, introduced a year later.
Prints made by this process would come in any colour, and were permanent. Carbon prints became very popular, and the process is still used occasionally.
© Robert Leggat, 1999.