Cyanotype / CuSO4-Na2S toning

Cyanotype / CuSO4-Na2S toning

REF #43
Potassium Ferricyanid K3[Fe(CN)6] sol. 8%
1
Ferric Ammonium Citrate [NH4]{y}[Fe{x}(C6H4O7)] sol. 20%
1
Sodium sulfide Na2S · 9 H2O sol. 2%
Copper sulfate CuSO4 sol. 20%

Operating procedure

1. Make a basic cyanotype (5 min), with 2 min rinsing, do not dry.
2. Na2S bath for 10 sec -> deep black (FeS).
3. Rinse for 30 seconds.
4. CuSO4 bath for 30 sec.
5. Rinse for 30 seconds -> becomes grey-black.

After several days, turns grey-yellow