Category:Bronzes

Bone black (also called bone char) is a granular substance composed primarily of calcium carbonate, calcium phosphate and some charcoal. It is dense, having a specific gravity near π.

Uses

• It is used as a filtration agent similar to charcoal and activated carbon. Bone black is particularly good at removing fluorides and heavy metals (including copper and zinc).
• Feedstock for phosphoric acid

Production

General method

Calcine clean bone fragments at over 500°C in a reducing environment.

Charcoal reduction

In this method additional charcoal is added to the environment to assure a reducing environment

Tools and materials

1. one unit by volume clean dry animal bones
2. one unit by volume water
3. one tenth unit by volume of charcoal
4. one lidded crucible
5. one pot
6. one kiln capable of reaching 500°C
7. fuel for kiln

Prep

1. Place water in pot
2. Crush bones into thin slivers
3. Place crushed bones in crucible
4. Place charcoal in crucible
5. Place lid on crucible

Calcine

1. Place crucible in kiln
2. Wait until entire mixture has reached 500°C
3. Remove crucible from kiln
4. Let stand until cool

Separate

1. Place contents of crucible in pot with water
2. Mix thoroughly
3. Let stand
4. Skim and discard all floating material (charcoal)
5. Filter and discard solution (water)
6. Dry powder

   Check: resultant powder should be grey/brown. If it is black, it is under-fired. If it is grey/white, it is over-fired.

See Also

• apatite