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How to Heat Treat a Knapping Stone

Heat treating flint knapping stone alters its structure, changing the stone's color and appearance, as well as making it easier to work. Flint knappers heat treat their own raw stone in fire pits, oven roasters or kilns. When first experimenting with the process, a fire pit is a cheaper alternative than a kiln and more readily available. A roaster is affordable but not as safe as burying the stones, which do get very hot and can explode. It's possible to dig a fire pit in the backyard with little effort.

Things You'll Need

Shovels
Sand
Flint
Charcoal
Wood
Matches
Rake
Fire-proof gloves
Hammer stone

Instructions

- 1
  Dig a fire pit deep enough to hold flint, sand and a fire --- about 2 feet deep.
- 2
  Line the fire pit with a layer of sand. Place flint stones on top. Cover with a 3-inch layer of sand.
- 3
  Cover with charcoal or wood and start a fire. Keep the coals from the fire going for 24 hours. Add more fuel as needed to keep the coals hot during this time.
- 4
  Scrape the coals aside. Dig out the sand and recover the flint with 1 inch of sand.
- 5
  Cover the sand with coals again and add more fuel to keep the pit hot for 12 hours.
- 6
  Let the coals cool down. Leave the stones buried for 48 hours to cool down completely.
- 7
  Dig up the stones and test to see if they are heat treated to satisfaction. If not, recover them and repeat the process.

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