Author Topic: Verdigris on silver  (Read 1978 times)

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Offline bruce61813

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Re: Verdigris on silver
« Reply #15 on: April 19, 2018, 05:12:50 AM »
If you have an oven with a pilot light, leave them in there overnight. You may have to flip to expose the other side. Or a sunny windowsill for a couple days will do it.

Bruce

Offline altaycoins

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Re: Verdigris on silver
« Reply #16 on: March 27, 2019, 03:32:02 PM »
This verdigris on silver is different than verdigris on copper. It is actually not inherently part of the silver mixture but a result of deposition of copper on silver from an outer source when the coin in contact with soil.

Considering the silver enbrittlement over the decades, I would not prefer to expose coin to freeze-boil cycles as it might result in breakage.

10% formic acid solution is the best solution for such deposits. Formic acid only reacts with copper and forms copper formate which is a very soft compound that can be easily removed by mechanical force using a toothpick or something similar.

Offline THCoins

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Re: Verdigris on silver
« Reply #17 on: March 27, 2019, 06:06:47 PM »
I have used formic acid, but i would advice it only on coins of fairly pure silver. On billon coins with a low silver content i quickly found out this was not a good idea.

Offline bruce61813

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Re: Verdigris on silver
« Reply #18 on: March 27, 2019, 06:50:10 PM »
I have used the soda/soda mix to soak similar coin in. It will remove some of the copper oxides, and being a base, won't harm the silver. These coins probably have a copper component, for strength.


B

Offline altaycoins

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Re: Verdigris on silver
« Reply #19 on: March 27, 2019, 06:57:34 PM »
I have used formic acid, but i would advice it only on coins of fairly pure silver. On billon coins with a low silver content i quickly found out this was not a good idea.

Ah for sure, if you are not sure about the silver content, I would not recommend to use this method. Or can be tested on the edge of the coin on a small spot before applying to entire coin.

Offline Figleaf

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Re: Verdigris on silver
« Reply #20 on: March 27, 2019, 10:54:13 PM »
I have used formic acid

That's all good and well for pharmacists and chemists and doctors, but if you are a less exalted human being, at best you can order it in Bulgaria and the smallest quantity is enough for about 15 000 coins. Now, if you tell me it's the main ingredient of eye shadow or Coca Cola, that would be something I can work with :D

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

Offline bruce61813

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Re: Verdigris on silver
« Reply #21 on: March 28, 2019, 02:15:24 AM »
Formic Acid or Phosphoric Acid?  Most soft drinks have Phosphoric acid, the sting from ants is caused by Formic acid.

Bruce

Offline THCoins

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Re: Verdigris on silver
« Reply #22 on: March 28, 2019, 10:12:41 AM »
Quote
tell me it's the main ingredient of eye shadow or Coca Cola

No need to go to the chemistry bulk store. In the Netherlands you can get "Antikal", a cleaning spray for bathrooms. Its main active ingredients are Formic acid and Citric acid. Warning: Do not use in pure form, and rinse of treated coins very thoroughly !

Offline Figleaf

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Re: Verdigris on silver
« Reply #23 on: March 28, 2019, 11:07:56 AM »
Thank you. I think I prefer that to rubbing the coin with angry ants ;)

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

Offline bruce61813

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Re: Verdigris on silver
« Reply #24 on: March 28, 2019, 06:51:12 PM »
 >:D Spoil Sport!  ;D You try a little CokeCola on a cotton swab to see if it works. Rinse after.

Bruce

Offline Figleaf

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Re: Verdigris on silver
« Reply #25 on: March 29, 2019, 09:32:26 AM »
A little on a cotton swab may work, but I heard of people who'd leave the coin bathed in Coke for a period. The coin was clean and ruined, of course. Maybe I shouldn't have mentioned Coke, but it was hard to think of something with more highly doubtful ingredients. :P Prefer angry ants to Coca Cola.

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

Offline altaycoins

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Re: Verdigris on silver
« Reply #26 on: March 29, 2019, 04:47:44 PM »
A little on a cotton swab may work, but I heard of people who'd leave the coin bathed in Coke for a period. The coin was clean and ruined, of course. Maybe I shouldn't have mentioned Coke, but it was hard to think of something with more highly doubtful ingredients. :P Prefer angry ants to Coca Cola.

Peter

I totally agree, I wouldn't even use "Antikal" as you may still don't know the exact composition. My strategy is to get the chemical as pure as possible and then dilute as needed.