Argyrotype

Content sourced from Wikipedia, licensed under CC BY-SA 3.0.

Argyrotype is an iron-based silver printing method that creates brown images on ordinary paper. It’s related to 19th-century processes like Argentotype, Kallitype, and Van Dyke but is simpler to use, more stable, and has a longer shelf life for the sensitizer. It was developed by Mike Ware in the 1990s. The key chemical is silver sulfamate, which you can make on site from sulphamic acid. The sensitizer works slowly, so you print by placing a large negative in contact with the paper and exposing it to UV light or sunlight. Like other alternative processes, you can tweak the process for different effects, and because it’s printed on plain paper you can combine it with drawing or printmaking techniques.