Chromogenic or C-Type printing was the dominant method of colour printing since the process was invented in 1935. Originally, C-Type prints were made in a darkroom using traditional wet chemistry, and the colour negative was exposed to paper that contained 3 gelatin layers containing cyan, magenta and yellow dyes, which together created a full colour image. After the image had been exposed it was submerged in a chemical bath, where each layer reacted to the chemicals to create the full colour image. Because the chemicals are so complex, the image continues to react even after the process is completed. The chemicals are also extremely sensitive to water, light and heat, making it difficult to protect C-Type prints from deterioration. They can be prone to colour shift or fading without archival framing and minimal exposure to sunlight. The process was an early method for producing large scale prints. ‘C-Type’ was originally the trademark of Kodak, for the paper they used for making prints from colour negatives, and in 1942 the process gained popularity through Kodak’s ‘Kodacolor’ prints which were hailed for their ease, consistency, quality and affordability.
Today, C-Type prints are made digitally using LEDs or lasers to project an image onto sensitised paper and then developed using the same traditional wet process as above. They can also be produced as a hybrid of digital and darkroom processes, where digital images are projected onto paper using an enlarger, and then the wet chemistry process is performed by automated machinery.