Author Topic: Cleaning black and green spots on 1/4 anna 1906 XF+  (Read 901 times)

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Offline Robichari

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Cleaning black and green spots on 1/4 anna 1906 XF+
« on: February 24, 2020, 10:53:48 PM »
Hi!

It is 1/4 anna 1906 bronze variation.
How can I clean the black spots on this coins in such way that dont damaged it?
I think it is begining of something dangerous for coin. And how next prevent this things in future?

Thanks!

Robert

Offline Figleaf

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Re: Cleaning black and green spots on 1/4 anna 1906 XF+
« Reply #1 on: February 26, 2020, 01:52:41 PM »
Coins that have retained some of their original metal colour are very difficult to curate. It is natural for the metal to change from bright orange to a shade of brown. This process has started on your coin. It cannot be undone without damaging the coin. The only way to stop it is to isolate it from oxygen with Renaissance wax.

The green spots are another story. Here, the culprit is not oxygen, but moisture. It has already eaten into the metal, but an attempt to remove it will increase the damage. The only thing I can think of is to wash the coin in lukewarm, soapy water. Mop up water afterwards and dry very well, preferably on a heating element or in sunlight. This will mainly remove fat, but it should also remove the top layer of the green spots. Cover with Ren wax or lock the coin in a good quality airtight capsule with rubber ring when the coin is totally dry.

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