Cyanotype / CuSO4 toning

REF #39

Potassium Ferricyanid K3[Fe(CN)6] sol. 8%

Ferric Ammonium Citrate [NH4]{y}[Fe{x}(C6H4O7)] sol. 20%

Copper sulfate CuSO4 sol. 10%

1. Make a basic cyanotype (5 mins), with 10+10s rinsing, do not dry
2. CuSO4 bath for 30 seconds
3. Wash 3 times for 30 seconds