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Sidero-Cupreatype / Colouring Tannic acid - caustic soda

REF #61

Grey brown Grey yellow Black Tan / Sable

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

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

Ammonium copper citrate (NH₄)₂Cu(C₆H₅O₇)₂ sol. 20%

Caustic soda NaOH sol. 0.1%

Tannic acid C76H52O46 sol. 7%

365nm

Operating procedure

Make a normal sidero-cupreatype (sheet #3) with:
- 6 minutes exposure
- 30+30 seconds rinsing
Caustic soda bath for 10 seconds
Washing for 30+30 seconds
Tannic acid bath for 1 minute
Washing 3 times for 30 seconds

The blacks are very deep, the deepest of the siderotype variants, I think.

Consignes de sécurité

Corrosive product: Handle with nitrile gloves and safety goggles.

Beware of bleach vapours. Never mix with a base.

Be very careful when handling lye, as it is highly corrosive and extremely dangerous to mucous membranes. Start with a product that is already diluted, such as Destop (10%).