Nitrosotype

Nitrosotype is a historical photographic printing process that produces images with a distinctive bluish-brown or purplish tone. It was developed in the late 19th century by William Willis, who also invented the collodion-carbon process. The process involves coating paper with a light-sensitive solution containing nitrocellulose and silver salts. When exposed to light, the nitrocellulose undergoes changes that make it insoluble in water, creating an image. The image is then developed in a solution that reacts with the silver salts to produce the characteristic color.

The nitrosotype process was known for its ability to produce fine detail and a wide tonal range. It was particularly popular for portraiture and landscape photography. However, it was also a complex and somewhat unstable process, with prints sometimes fading or discoloring over time. Due to these limitations and the rise of more convenient photographic methods like gelatin silver prints, the nitrosotype process gradually fell out of favor and became largely obsolete by the early 20th century. Today, it is considered a historical photographic process, and contemporary practitioners sometimes revive it for its unique aesthetic qualities.