Van Dyke

This version uses oxalic acid, which makes the result more predictable.
It also requires less exposure time.
The colour is also darker, much less chocolatey.

All under a safelight:

1. Mix the citrate, oxalic acid and nitrate.
2. Spread the mixture onto the paper.
3. Expose. (5 min).
4. Wash for 4 x 30 seconds.
5. Fixer bath for 30 seconds.
6. Wash for 30 + 30 + 30 seconds.