Bone ash

Bone ash is the white, powdery ash left from the burning (calcination) of bones. It is primarily composed of calcium phosphate. It is commonly used in fertilizers, polishing compounds, and in making ceramics (such as bone china). It also has historical uses in the manufacture of baking powders and assay cupels.

Although synthetic alternatives have been produced (synthetic tri- or dicalcium phosphates), the majority of bone china is still made using natural bone ash. Synthetic bone ash has also found use as a mold release agent for the casting of non-ferrous metals such as copper.