I have bought a Parthian coin ( Phraates IV ). the seller told me that it has been cleaned by electrolysis . now there is a black flim attached on the coin . it was 6 months in olive oil . but didn’t chanch. . what must I do? Can I clean it? Or is better never try to clean it?
I really suggest leaving the coin as it is. The black surface appears to be a hard and stable so removing it would leave a rough and porous scrap of copper worthless on the market. The coin looks better than many Parthian bronzes I have seen. I am a little confused by the claim that it was cleaned by electrolysis since this usually removes patina along with the crusts so either the cleaner was better than most or the coin has been artificially retoned. Either way it looks better now than it would scrubbed down to new penny brightness.
I agree with Doug. This coin has not seen electrolysis unless it was VERY short in duration. Electrolysis is only suited for coins that are effectively valueless and unknown without electrolysis, and cannot be cleaned any other way. In other words, you clean coins every way imaginable, and the slugs left over you can electrolyze, since they are goners anyway. This coin is dark maybe because of the olive oil. I am not a big fan of it because it darkens coins. I would put it in a pure water bath for a few weeks, changing the water every few days. This may lighten the coin a little, and may lessen the deposits. Its ok if it doesn't, since this coin is in good shape for a Parthian bronze. Just make sure you buy purified water and do not use tap water, since tap water contains chlorine which cn lead to bronze disease. Another cheap source of the water is the runoff from air conditioners, which in Iran I am sure you run often in the summer. Btw, great to meet you Mani. I am a huge fan of your country and culture, having collected Sassanid coins many years. I wish more westerners knew the story of your great civilization. Chris EDIT: Just to clarify by "pure" water I mean distilled.
