Black patina on silver coins

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Hello,

How to create such black patina on silver coins, as on the picture at the bottom of coin:


Some coins from auctions have it, and I think that it is "artificially created", how ?
I think its just natural patina reappearing after the coin had been previously cleaned.

I had some coins stored for long time which have beautifull colored patinas which have appeared but I have also some which have turned directly to a black patina which is usually called tarnish as its not perceived as being something very attractive to a coin.

Of course some contact to some chemicals or improper handling or improper storage to humidity etc. can also accelerate such a process and that not always in a positive way.
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Those very dark ones, I suspect they have been damaged before. Metal Corrosion is the cause. Those with normal patina, is due to 2 reason.

Stored in a open air for a long time.

Stored in album in long time.

Stored in album will slow the process. Keeping it air tight with anti tarnish strip will reduce the process of they become dull. And do not put the anti tarnish strip on top of the coin!

I have not yet try a experiment due to not enough time. Below is a example of tarnish coins that has been stored together with different metal coins. (I am not able to load the pictures on my phone... See the forum link)

https://en.numista.com/forum/topic81571.html

I suspect those coins even if I use those metal polisher, they will appear black after some time with the same toning. Its a experiment I am going to try next after I have time.
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around the edges, can be from contact with coin album pages made of cardboard of ordinary paper, which may contain chlorine or sulfur compounds.
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As an ex gold and silversmith I have had some experience with the act of making silver items look like an antique. This involved rubbing the item with hydrogen sulfide (an acid, chem: H2S) and then lightly polishing it.
The H2S will cause the entire item to go black (by forming a coating of silversulfide) and the light polish will restore highlights again.
Even a light polish can be quite aggressive though, so I would not recommend doing this with coins.
Note that the above I have used on silver items only. I know for fact that there is a product to do something similar with gold items (for a dark brown patina). And as for bronze and brass, considering the copper content in those two alloys, I am sure that some experimenting with certain acids could produce artificial patina as well. For copper-nickel, steel and aluminium I do not believe an artificial patina can or should be created.
On a side note: many silver jewellery items are Rhodium or Nickel plated, if this were not so than the Sterling Silver jewellery we wear would also blacken in the recesses of the item. For some reason, the extent of this varies between people.
Thank you guys for interresting ansvers.
Quote: "LEÓNIDÁS"​Hello,

​How to create such black patina on silver coins, as on the picture at the bottom of coin:


​Some coins from auctions have it, and I think that it is "artificially created", how ?
​Hi LEÓNIDÁS
Yes it is, they use sulfur. I asked the merchant how he'd done that long ago. He was a chemist, gave me sulfur flakes. I went on a bronze coin ruined and scraped, I went on a bronze coin ruined and scraped, so I resigned from it.
I made an attempt for you-an example of a silver groschen fragment.
When you go to Slovacko- famous Boršice , after a few kilometers from Boršice I live, I'll give you sulfur in the bag. And look at the coins.

Experimental fragment: silver

flakes of sulfur.

one small flakes dissolve into water:

result:

Photos aren't clean it's a quick try.
Ahoj Ivan
Quote: "MIMAEL"
Quote: "LEÓNIDÁS"​Hello,
​​
​​How to create such black patina on silver coins, as on the picture at the bottom of coin:
​​
​​
​​Some coins from auctions have it, and I think that it is "artificially created", how ?
​​Hi LEÓNIDÁS
​Yes it is, they use sulfur. I asked the merchant how he'd done that long ago. He was a chemist, gave me sulfur flakes. I went on a bronze coin ruined and scraped, I went on a bronze coin ruined and scraped, so I resigned from it.
​I made an attempt for you-an example of a silver groschen fragment.
​When you go to Slovacko- famous Boršice , after a few kilometers from Boršice I live, I'll give you sulfur in the bag. And look at the coins.

​Experimental fragment: silver

​flakes of sulfur.

​one small flakes dissolve into water:

​result:

​Photos aren't clean it's a quick try.
​Ahoj Ivan
​Ahoj Ivan,

Thank you for advice, I have also some sulfur, I will try it on any dead silver coin.
Black toning on a coin is caused by the silver reacting to sulphur. You can create it artificially by sticking the coin in a container with some mashed eggs.
What? Me Worry
Quote: "neilithicman"​Black toning on a coin is caused by the silver reacting to sulphur. You can create it artificially by sticking the coin in a container with some mashed eggs.
:DI will try also this. Just for experiment.
So, I have done experiment with garlic and onion which also contains lot of sulfur and result is interesting, patina is brown.

With the mashed egg you put the coin at one end of a container or bowl, the egg at the other end and then cover with a lid or plastic cling-wrap. It's a bit cheaty to do it to try and make new coins seem old, but it is good for restoring the toning to coins that some foolish sod has dip-stripped all the original toning off.
What? Me Worry
Quote: "LEÓNIDÁS"​So, I have done experiment with garlic and onion which also contains lot of sulfur and result is interesting, patina is brown.

​and the coin now smell like....dinner? :O
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