I have a number of Chinese cast iron coins. Naturally they are rusty, being up to 1000 years old. Should I do anything to conserve these coins, such as brush them with oil, or should they be left strictly as is? Your opinions/suggestions would be much appreciated.
The answer is: "I don't know." My brother and I had a discussion about tools. I inherited some fine old early-20th century tools when my father-in-law passed away. What do to? On another tack, years ago, I bought a WWI German bayonet. Nice tool, but should I sharpen it and oil it, etc., so that I could use it for camping? A dealer said to go buy a camping knife and put the bayonet on eBay: "Don't mess with it." In the 19th century, some collectors were in the habit of varnishing their coins. Even into the 20th, some collectors used clear nail polish or other laquers to preserve their coins. Fortunately, you can remove the laquer from a copper or silver coin with solvents that do not change the surfaces of a coin. In this case, to bring the question back to iron, the truth is that if you do nothing, the coins are going to rust... forever... until there is nothing left... The only way to fight rust is to use the tool. You cannot oil an axe or a file or calipers or a divider and prevent rust. Only using a tool keeps the rust off. Hence, in popular talk, we say, "I'm getting rusty..." On the other hand, if you oil it - WD40 or Kroil or other - you are going to change the coin from an original coin to one that has been treated. One way to consider this is that in the 1000 years since the Sung Dynasty, your coins have survived. If you do nothing, they will likely survive your lifetime and that of your heirs. Again, in the 1930s and 1940s, the Boy Scout Handbook, discussing the Coin Collecting Merit Badge, recommended "brightening" your Indianhead and Lincoln Cents by rubbing them with a pencil eraser. Hopefully, you would not do that now. Most dealers say, "If you don't like the coin in that condition, then don't buy it in that condition." Unless you have some sort of certification in Coin Conservation, all you are going to do is enroll yourself in the Legion of Collectors Who Messed Up Their Coins. That said, Chinese iron being what it is, if you have to do this, be gentle. One thing I found with oil is that a little bit goes a long way. Olive oil is preferred over mineral oils. Light oils are preferred over heavy oils. Doing nothing is the safest route.
I think that, due to the unstable nature of the metal, you have no choice but to treat them. Which is better, a treated coin, or an original blob of rust?
Thanks Folks. To date all I have done is remove any loose rust with an old toothbrush. I'll try a little oil or maybe petroleum jelly on a cheap coin and see what it looks like. Before and after scans will follow when I have done the deed, which won't be for a few days as we have a family wedding disrupting life at present. Cheers Richard
Not sure whether I like the result or not, although the coin shouldn't rust any more for a while at least. I applied a little petroleum jelly, and gave the coin a light brushing with a bronze brush. What's the general verdict?
