Author Topic: Advice needed.  (Read 1337 times)

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Offline Hitesh

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Advice needed.
« on: October 24, 2014, 08:47:27 PM »
Hey,
I've been reading the previous posts related to cleaning coins on WoC. I take it that coins generally should not be cleaned as it might have an adverse effect. But, one thing I'm not clear on is that will oxide compound formation further lead to deterioration of the coin?

In the attached silver punch marked coin for example there is limited formation of green oxide. Will this oxide continue to fester on the whole coin? So does it need to be removed or not?

Also, will it be any different for any other metal coin e.g. copper?. In bronze coins the oxide formation needs to be removed at the earliest(according to this topic relating to bronze disease : http://www.worldofcoins.eu/forum/index.php/topic,134.0.html ). Is there a similar case with any other metal too?

I am not inclined to clean the coins in the question unless there is a chance of losing the whole coin.

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Offline Figleaf

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Re: Advice needed.
« Reply #1 on: October 25, 2014, 10:16:55 AM »
I think your take on cleaning a coin is somewhat too strict. May I reformulate that as: you should not clean a coin when you don't know yet what you are doing? There's plenty of information on this board so that by the time you start restoring (the better verb once you know what you are doing) you will not damage the coin unduly. My approach is that anything that is in the way of reading the coin or seeing the design properly should be removed. I would give your first coin a month long olive oil bath, which will do nothing to the patina, but it will soften the oxide, take some off and solve any remaining crud. Next, I would wash the coin in clean water to take off excess olive oil and rub the green spot lightly to remove softened green stuff. Dry well. If I were still unhappy with the green, I would scrape some off with a wooden toothpick (metal is harder than wood, so that would leave no traces).

The above is on the assumption that the green spot is oxide, which I think it is, not copper pest. If it is copper pest, every trace of it should be totally removed or it will destroy the coin. Use pins, needles or dentist hooks to take it all off and never mind any scratches. You will have to decide on whether it is copper pest or not first. There is information on this board to help you. In general, oxide tends to be dust-like and green, while copper pest looks more like green-blue and blister-like. If you are in doubt, take a picture of your coin, leave it alone in a dry environment (important) but compare the coin with the picture regularly. If the green spot grows in size, it is copper pest. If it is not growing, it is oxide.

Peter
An unidentified coin is a piece of metal. An identified coin is a piece of history.

Offline Hitesh

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Re: Advice needed.
« Reply #2 on: October 25, 2014, 08:16:06 PM »
Do silver coins also have some kind of "disease" that can ruin the whole coin? This punch marked coin has some slight green oxide formation.

Can this spread to the whole coin?

Thank you for the help!
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Offline Figleaf

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Re: Advice needed.
« Reply #3 on: October 25, 2014, 09:26:24 PM »
Nothing is ever simple. Silver doesn't have a similar problem. However, coins are not made with pure silver. Silver oxide is black. Therefore, the punch marked coin's green spots can be either internal: from the copper in the coin, or external, from having been close to copper objects. Internal is likely only if either the coin has a pretty high copper content or if the copper and silver are badly mixed. Punch marked coins are in good silver. There is so little copper in them, that it is highly likely that the green came from an external source. Therefore, it will not spread. It is quite probably oxide, not copper pest.

It seems likely that you can easily wipe off the green. Try a soft eraser. It will also remove loose dirt and generally improve how your coin looks. Just don't overdo it. Stop when you are happy with how the coin looks. Don't forget the coin's edge.

Peter
An unidentified coin is a piece of metal. An identified coin is a piece of history.

Offline Hitesh

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Re: Advice needed.
« Reply #4 on: October 26, 2014, 02:48:03 PM »
Will do that definitely!
Thanks a lot for the help!
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