bone ash
Refers to the ash obtained by burning bones, used in ceramics, fertilizers, or as a material.
Bone ash is sometimes used in ceramic glazes.
この肥料には骨灰が含まれている。
This fertilizer contains bone ash.
Standard kanji spelling for 'bone ash'.
Compound of 骨 (bone) and 灰 (ash). The reading こっかい is a regular sound change from こつ + はい.