VanDyke Brown

The VanDyke brown print is an iron-silver process based on the argentotype invented by John Herschel in 1842. The process gets its name from its deep brown color that is similar to that of the pigment used by Flemish painter Van Dyck.

http://www.alternativephotography.com/wp/processes/kallitypes/vandyke-notes

Three solutions were made with distilled water: one with ferric ammonium citrate, another with silver nitrate, and the last with tartaric acid. The solutions were mixed together while stirring. The liquid was a pea green color and occasionally needed stirring before applying to our 100% cotton rag paper. 

To sensitize our paper, we simply brushed on coat of the mixture onto the paper. We then exposed our paper with a negative out in the sun for about 5 minutes.