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Sidero-Cupreatype / Chrome alum toning

Sidero-Cupreatype / Chrome alum toning

REF #76
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Ferric Ammonium Citrate [NH4]{y}[Fe{x}(C6H4O7)] sol. 20%
1
Potassium Ferricyanid K3[Fe(CN)6] sol. 8%
2
Ammonium copper citrate (NH₄)₂Cu(C₆H₅O₇)₂ sol. 20%
1
Chrome alum KCr(SO4)2·12(H2O) sol. 2%
365nm

Operating procedure

Make a normal sidero-cupreatype (sheet #3) with:
- 6 minutes exposure
- 30+30 seconds rinsing
Alum bath for 2 minutes
Washing 30+30+30 seconds