It involves coating a canvas with ferric ammonium citrate, tartaric acid, and silver nitrate, then exposing it to ultraviolet light.
The canvas can be washed with water, and hypo to keep the solutions in place.
[1] The image created has a Van Dyke brown color when it's completed, and unlike other printing methods, does not require a darkroom.
[2] The Van Dyke brown process was patented in Germany in 1895 by Arndt and Troost.
[3][4] Concerns have been voiced about the archival qualities of the Van Dyke brown print due to the fact that many early Van Dyke brown prints did not last long.