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 Replies: 9 / Views: 1,152 |
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Pillar of the Community
Canada
6244 Posts |
Quote:
Once the die has been polished and frosted where appropriate, it goes to a clean room to receive a thin plating of chrome. The die is placed in a vacuum chamber for a process called physical vapor deposition (PVD). Chrome, in vapor form, coats the surface of the die. The chrome protects the design during striking.
After the PVD process, an employee buffs out any imperfections and gives the die a final inspection. It's finally ready to use From the Mint the procedures in place for Proof Dies. I wrote this because by the last studies, I was involve also, we find that the spots on the proof coins is cause by small particles of chrome which detach from the Die to the coins. Those small particle will oxide faster then the coin material and cause the small flat, matte spots. No one can say after how many strikes this occurs. Studies are in the way to adjust this anomalies, in my opinion vanadium will be the best. Is to follow. Hope many give the opinion to help the studies. PS: Personally I do not want to buy a 3K coin which has spots after 1,2 or 3 years. Thanks. Edited by silviosi
09/23/2022 03:03 am
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Bedrock of the Community
Australia
21788 Posts |
Like Cr, V is also used for hardening of machine steels.
For the Mint, it may well turn out to be a better metal for PVD.
Perhaps it may present the same problems and advantages of Cr die plating; that is up for the Mint to discover with practical experimentation.
Review of clean room environment may well have to be improved, in either case.
I feel sure that the Mint doesn't want to sell a potential $3k coin that degrades in too short a time, and they are well aware of this problem.
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Pillar of the Community
 Canada
6244 Posts |
@SEL: Yes they are aware of this. I post for the knowledge and a also of how the community see. Me I propose vanadium. Is not perfect but more stable. One of the main issue at the mint are the collectors to be happy.
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Pillar of the Community
United States
713 Posts |
Interesting, what do these spots look like [size, shape, etc]? Do they grow over tine?
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Pillar of the Community
United States
1233 Posts |
Does anyone know is there a way to deal with the spots after this has happened with out damaging the coin
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Moderator
 United States
98746 Posts |
Hey Silvio, are you refering to the 'Milk spots' that appear on the mirrored finishes of the fields?
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Bedrock of the Community
United States
62064 Posts |
Best to not alter a proof coin. The damage you might create might turn it into a cull coin to a serious collector.
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Pillar of the Community
United States
2004 Posts |
I thought that "Milk Spots" were the result of improper washing of the planchets to remove the cream of tarter solution. A big problem with early silver eagle coins. Can anyone expand on this?
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Pillar of the Community
Canada
6244 Posts |
Yes I talk about the "Milk spots", and I can say that I have no idea if could be clean or not. Anyways, I will not sacrifice a valuable coin for testing to find out because to perform testing in this matter is meaning to perform destructive tests.
Hope the R&D labs and the assays centers will find the solution. I know Austria eliminate this problem but how they done I have no idea. Probably the Mint is already in contact with.
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Bedrock of the Community
Australia
21788 Posts |
If proof coins cost more to produce because a more exacting quality control is required,
they will cost more to buy, to cover the higher production costs.
The secondary numismatic after market will still determine if they are turn out to be a good buy for the original purchaser.
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Replies: 9 / Views: 1,152 |
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Posted 09/23/2022 02:59 am
