Bone black is blue-black in color and fairly smooth in texture and also denser than lamp black. It contains about 10% carbon, 84% calcium phosphate and 6 % calcium carbonate. It is made from charring of bones or waste ivory. It was used from prehistory and it is in use until today. Ivory Black is therefore the least pure form of carbon black, containing a high percentage of calcium phosphate.
Bone black is prepared by charring bones, horns etc. in the absence of air. It is the deepest black but it was not used as widely as charcoal black. Fragments or turnings of ivory, or of the osseous parts of animals are put into a crucible surrounded by burning coals and covered. The ivory or bones, by exposure to the heat, were reduced to charcoal.
Charred bones itself has also found its use in many applications outside of just pigments. One interesting example, is its use in decolorizing sugar, as well as wine and vinegar. Charred bones, used to make the deepest of blacks, is also the reason for the pure white sugar bought from store shelves.
Chemical name: calcium phosphate + calcium carbonate +carbon
Ca3(PO4)2 + CaCO3 +C
|Color Index (C.I.)