Copper Oxide Black CuO

1 – 5% addition

These strong colouring oxides and compounds give an apple green colour under neutral or oxidising conditions, except in alkaline glazes when a turquoise blue is obtained. Whilst in reducing conditions a copper red colour is produced sometimes known as sang-de-boeuf.
NOTE – when added to low solubility glaze, copper causes the solubility of the lead to be greatly increased, making the glaze unsuitable for use on vessels containing foodstuff or beverages.