BROWN OKHRA
Brown okhra ( ochre for English) is a tobacco colour pigment tinted by hydrated iron oxide and haematite ( iron oxide), which are found mixed with gypsum and calcite in this particular earth.
Chemical formula Fe2O3 • nH2O (9-10,5%) + CaCO3 (25-30%) + CaSO4 (30-35%)
Stability to light 7 (scale 1/8)
Specific weight 3,50
For fresco, tempera, oil, encaustic
