Van Dyke process was invented in Germany in 1895 and similar to cyanotype in some ways. It got its name from the 17th-century Flemish painter Anthony Van Dyke. Its a "print out process" - POP using chemicals and a fixer of Sodium Thiosuphate to alter the colour and fix the print. The chemistry consisits of
Solution 1: Dissolve 10 grams ferric ammonium citrate in 30 ml distilled water.
Solution 2: Dissolve 1.5 grams tartaric acid in 30 ml distilled water.
Solution 3: Dissolve 4 grams silver nitrate in 30 ml distilled water.
Combine the 3 solutions and stir well. Add enough distilled water to make 100 ml of solution. The solution will keep for several weeks if stored in a cool, dark place. It is coated on a non acid water colour paper and the image is contact printed from large format negatives with UV light. Wash in plain water followed by the fixer for a few minutes and the final water wash before drying.