cowhodan Posted February 15, 2006 Report Share Posted February 15, 2006 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? Thanks Link to comment Share on other sites More sharing options...
gxseries Posted February 15, 2006 Report Share Posted February 15, 2006 I am not too sure if acetone will be effective. By proof gold coins, I am assuming that it is either .900 or .999. If it is 999, using acetone should not cause problems. But on 900, I am not too sure. I believe ageka has done a serious test on what acetone will do on gold coins. I will let ageka do the typing... Link to comment Share on other sites More sharing options...
gxseries Posted February 15, 2006 Report Share Posted February 15, 2006 *del* Link to comment Share on other sites More sharing options...
jtryka Posted February 15, 2006 Report Share Posted February 15, 2006 If it's a .900 fine gold coin it sounds like copper spots developing. I am not sure what acetone might do, but I know that NCS has had success in removing copper spots from gold coins. Link to comment Share on other sites More sharing options...
cowhodan Posted February 15, 2006 Author Report Share Posted February 15, 2006 Its .999 gold, is it possible that they are copper spots? Link to comment Share on other sites More sharing options...
jtryka Posted February 15, 2006 Report Share Posted February 15, 2006 I could be wrong, but I don't think you could get copper spots on .999 fine gold since it's pretty much pure. Copper spots are common on .900 fine gold as it was often alloyed with 10% copper and silver. Link to comment Share on other sites More sharing options...
jlueke Posted February 16, 2006 Report Share Posted February 16, 2006 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? Link to comment Share on other sites More sharing options...
ageka Posted February 16, 2006 Report Share Posted February 16, 2006 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 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 So for the moment I am leaving the stains on the coin and will first read my new book on coin preservation Link to comment Share on other sites More sharing options...
cowhodan Posted February 23, 2006 Author Report Share Posted February 23, 2006 Thanks for the replies, I'll use acetone and see what happens, I dont think it can get worse.. Link to comment Share on other sites More sharing options...
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