Better get myself some sawdust and paraffin. The second cleaning of the silver/copper coin was of particular use over just citric acid, and the copper coin conservation was also interesting. Thanks for putting that up Colin.
The acid foil reaction works very well, just tried it this morning on some coins and rings that I couldn't clean any other way. I just substituded the tartaric acid to citric acid and it worked well. Most of the coins were already toasted from being in the ocean but a small silver ring that was not already pitted came up a real treat.
The reaction is quite exothermic almost hot enough to burn so be careful, quite a lot of rotten egg (hydrogen sulphide) gas is expelled during the reaction too and it almost dissolves the foil used.