I bought a 1991 Australian Kookaburra from a dealer and it seems to have accumulated some sort of chemical damage from its holder. What do I do? Would getting a new holder fix the problem and would it be a good idea to somehow clean the coin? Thanks
Hopefully those are good enough. As you can see in the first picture there is a lot of buildup on the right side and from the second pic you can see that it goes all around the edge of the coin. It has definitely gotten worse from the day that I bought the coin about half a year ago.
Doesn't look like PVC to me, more like tarnish (toning) this happens a lot on silver coins and shouldn't cause a problem, if it toning spreads and looks pretty, people might buy it for a slight premium.
I agree - it's just toning. Especially if the coin has been kept in that holder the entire time - it could not be PVC because that holder doesn't have any.
Doug is correct. It's just toning and not due to the holder. Here's what you need to do. Put the coin in a freezer style ziplock bag with a desiccant pack and a BU copper cent. Squeeze out the air, and put that into another bag. Then store the coin properly and the toning will slow to a crawl. If the toning bothers you, sell your toned coin (likely for a premium) and buy an untoned coin.
Thanks for the info, I will wait to see how the coin continues toning and meanwhile buy another and try to keep that one from toning. Its nice that they release new designs for the Kookaburra.
Is the BU cent being used as a sacrifice to use up any reactive substances in the bag? A piece of zinc would do a better job.
It's same principle that intercept shield holders use. Any sulfides that enter the bag will react with the exposed copper. I'm curious as to why you think zinc would be a better choice chemically? IMO, zinc would be a very poor choice as it quickly forms zinc oxide which is very stable and non-reactive. This would defeat the purpose of the scarificial material to absorb hydrogen sulfide.
My thinking was that zinc is much more reactive than copper and would do a better job of reacting with any sulfides.
No as Badthad says zinc is very reactive but it is very reactive with oxygen. It almost immediately forms an oxide coating that slows or stops any further reaction. Copper is a much better choice for reacting with sulfides.
