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Acetone for gold proof coin?


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I have a mexican gold proof coin that has some red/brown spots, I have no idea where they came from as the coin is in its capsule but I dont like them, is it possible to use acetone on a proof coin to remove those spots or it will get damaged?



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Its .999 gold, is it possible that they are copper spots?


While it seems like a .999 should be free of copper spot problems, gold by itself really shouldn't spot at all. Acetone won't impact corrosion, some sort of dipping process might help but it might also make the area under the spots look worse. Maybe the coin is less pure than advertised?

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Due to time zones ( I am in Greenwhich plus one) I only saw the question now


Acetone is a pure solvent and will not arm any gold even 900

It only degreases and takes off non water soluble grease and dirt

and plasticizer from pvc flips

In winter the temperature maybe too low in your ventilated areas and if the acetone and the coin are not around 20 C there may be drying marks left and you will have to restart

The acetone really has to flash off leaving a cold clean coin

So I have a proof 9999 on which somebody sneezed and sold it

I will wait for summer to soak it again

I had a series of pictures on the old forum just do not know were I filed the originals :lol:


On the other hand I have a coin with red spots a 9999 gold proof and I tried

every solvent known to me without avail

A german university tracked down the problem

The gold and silver blanks are bought in austria ; the blanks of silver and gold are made on the same production line

Somehow silver gets on the gold blanks which then are stamped into coins in germany

the silver gets to be silversulfide which looks red on gold

The university proved the red spots were like 90% silver 8% copper and 2% gold

Everybody who got a purchase receipt was able to trade in the coins for new ones


So I am afraid the only thing that will help is silver dip and since the coins were struck after the contamination I think the cure may be worse then the ill :ninja:


So for the moment I am leaving the stains on the coin and will first read my

new book on coin preservation

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