Monday, April 03, 2006

Coin Cleaning with a Rock Tumbler

Small amounts of corrosion on coins (from being buried in the ground or from being left in a pool or fountain for too long) can be removed with a rock tumbler and a mild acid.

This is done by placing the coins in a rotary tumbler or vibrating tumbler so that the tumbler barrel is 3/4ths full. Add some water to cover the coins. For a large tumbler barrel add 1 cup of vinegar and let it run for about 6 hours. Check and if they are not done let them go longer. You can do this for up to 2-3 days.

For heavier deposits on the coins, you will have to mechanically remove the corrosion. Do this by placing the coins in the tumbler and adding 60/90 grit (1 pound per 10 pounds of coins) and letting them run for 6 hours. Rarely, they may need longer.

Some people add vinegar to the 60/90 grit for an even more effective corrosion removal. This requires removing the acid from the coins after they are finished. Do this by flushing them with distilled water for several minutes.

For small amounts of coins, you can use a small tumbler. Small tumblers are recommended for the prospectors who find occasional coins.

For companies and churches who have large numbers of coins, I recommend a 40-pound tumbler.

Coin Cleaning with Rotary tumblers vs. Vibrating tumblers:
Rotary tumblers take longer but are more effective and cost less.
Vibrating tumblers will NOT remove the heavy scale or corrosion. They will remove light scale and corrosion in 2-3 hours. If you have heavy corrosion and try to use a vibrating tumbler, you will not get the coins clean enough for a bank.

1 comment:

  1. Chris B10:36 PM

    Where can I find the gold colored or silver colored soft clasps that I can glue to some tumbled agates I have been collecting on the oregon coast? I would like to buy them in volume rather than buy them 1 at a time at a local bead shop. Any help would be appreciated! Thanks!

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