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Harshly Cleaned ancient silver denarius - get toning back?


Prieure de Sion

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Hello...

An acquaintance of mine bought two silver denarii of Gordianus III. However, both are "harshly cleaned". I told him to send them back to the seller if the coins were too badly cleaned and too shiny for him.

But the coins were quite cheap (25 euros each)- besides, the details of the two coins are otherwise extremely fine and they would look great in themselves. He would like to keep them.

He asked me if there is a way to get the shiny silver of the coins a little darker again. I have to admit, I don't know anything about that. Is there a way to make the silver a little duller / darker in a relatively short time? He just doesn't want them to be so shiny, but a bit duller and darker.

Thank you.

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7 minutes ago, John Conduitt said:

Anyway, you could just do what @Restitutor did (by accident). Leave them in warm sunlight, in the open air so they get plenty of sulphur. Handling them will probably help.

I just found something on the internet:

You take two hard-boiled eggs. You put them in a freezer bag. Add the silver coin. Then seal it. Then crush the eggs a little. Then put the bag in the light as you said. And leave it there. Then the coin becomes dull again.

He should do it like this 😄 

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8 minutes ago, Prieure de Sion said:

I just found something on the internet:

You take two hard-boiled eggs. You put them in a freezer bag. Add the silver coin. Then seal it. Then crush the eggs a little. Then put the bag in the light as you said. And leave it there. Then the coin becomes dull again.

He should do it like this 😄 

That's to get the sulphur in a very short time. Technically it's artificial, but it would be exactly the same.

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I've use liver of sulphur to darken coins that have been stripped in the process of treating BD. Never tried it on silver though. It will darken a coin very quickly, like within seconds, so care is required. Also, you'll want to rinse in a baking soda solution afterward.

I'm not sure, though, that any artificial process will give you that smooth and gentle look of a natural silver patina.

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3 hours ago, John Conduitt said:

I don't know if you could count it as harshly if they didn't otherwise harm the surfaces.

Anyway, you could just do what @Restitutor did (by accident). Leave them in warm sunlight, in the open air so they get plenty of sulphur. Handling them will probably help.

Awhile ago I found a good article on the mechanisms of how sunlight (or visible light in general) affects the toning of silver coins:

https://www.english-heritage.org.uk/siteassets/home/learn/conservation/collections-advice--guidance/effects-of-light-on-silver-tarnishing.pdf

In summary, it seems that exposure to visible light can "bleach" patinas formed of silver chloride (e.g. horn silver) so as to become white and dull, while for patinas comprised of silver sulfide the opposite happens. Silver sulfide provides a protective layer to silver coins, meaning as the toning develops the rate of toning slows down due to the protective effect of the silver sulfide layer. However, in the presence of visible light, the researchers found this protection was essentially lost and the coin would tone at rates comparable to those found on "clean" silver coins.

I just gave the article another quick read-through to write that summary so I may have missed some important points or forgotten something else but it does seem to indicate that some silver coins can tone faster under visible light but it's not clear whether a clean silver coin will tone any faster. Since the mechanism appears to be through the passivating of the protective patina layer, the lack of patina would probably mean the coin is toning as fast as it can, whether it's in sunlight or not.

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1 hour ago, Kaleun96 said:

Awhile ago I found a good article on the mechanisms of how sunlight (or visible light in general) affects the toning of silver coins:

https://www.english-heritage.org.uk/siteassets/home/learn/conservation/collections-advice--guidance/effects-of-light-on-silver-tarnishing.pdf

In summary, it seems that exposure to visible light can "bleach" patinas formed of silver chloride (e.g. horn silver) so as to become white and dull, while for patinas comprised of silver sulfide the opposite happens. Silver sulfide provides a protective layer to silver coins, meaning as the toning develops the rate of toning slows down due to the protective effect of the silver sulfide layer. However, in the presence of visible light, the researchers found this protection was essentially lost and the coin would tone at rates comparable to those found on "clean" silver coins.

I just gave the article another quick read-through to write that summary so I may have missed some important points or forgotten something else but it does seem to indicate that some silver coins can tone faster under visible light but it's not clear whether a clean silver coin will tone any faster. Since the mechanism appears to be through the passivating of the protective patina layer, the lack of patina would probably mean the coin is toning as fast as it can, whether it's in sunlight or not.

Interesting. I guess it depends on how much toning you need to stop a coin looking cleaned vs how much you need to slow toning down. Probably not very much in either case, as I believe you get the coloured tones with a layer of just a few atoms.

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I've found that really shiny silver coins, when they tone, still have a shiny appearance due to the altering of the surfaces from abrasion.  I recommend the gentle, slow approach, unless your friend is in a real hurry to darken the coins.  Keep the coins out and let time do its thing.

There is a solution called liver of sulfur - powerful stuff that has be used highly diluted.  Very smelly as well.  Experience is needed here to avoid having a silver coin turn black almost instantly.  That said, it is quick, but I still think the go slow approach is far better. 

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7 hours ago, CPK said:

I've use liver of sulphur to darken coins that have been stripped in the process of treating BD. Never tried it on silver though. It will darken a coin very quickly, like within seconds, so care is required. Also, you'll want to rinse in a baking soda solution afterward.

I'm not sure, though, that any artificial process will give you that smooth and gentle look of a natural silver patina.

Sorry, my mistake! I meant to mention that I am only looking for "natural" possibilities. I know Parisian oxide and sulphur liver. But I don't want to pass on chemical possibilities as a tip - I don't know how he applies them and what he does with them. And if in the end he should even suffer health damage - then I am also to blame. That's why I usually never give chemical tips to friends or relatives. But thank you, of course.

 

5 hours ago, Kaleun96 said:

Awhile ago I found a good article on the mechanisms of how sunlight (or visible light in general) affects the toning of silver coins:

That's interesting - I'll read that later...

 

1 hour ago, robinjojo said:

There is a solution called liver of sulfur - powerful stuff that has be used highly diluted.  Very smelly as well.  Experience is needed here to avoid having a silver coin turn black almost instantly.  That said, it is quick, but I still think the go slow approach is far better. 

Thank you very much - as already mentioned - I will not give him chemical tips.

 

He should actually try the egg trick and the sun. That way he won't damage his health and the coins won't break right away. 

I'll tell him to please take pictures - before and after - and I'll post them here.

 

PS: Or he should send the coins to @Restitutor - he can then charge 20 euros per coin for toning.... 😄 😄 😄 

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18 hours ago, AETHER said:

With ancients, harshly cleaned means scratches to me, but if its just to bright, but the surface is good, no biggie, any original luster is usually gone anyway, and it will retone, naturally or you can speed up the process. 

I have seen the coins today - and there are no scratches (from cleaning) - but they will shining un-natural .... they are sooooo shining. I told him, he can try the egg trick - or let them outside and wait. 

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I tried the egg trick a few days ago. I didn't expect to post this here so unfortunately I only took photos after toning, not before.
There were some reasons why I tried it on these 2 coins. The Julia Mamaea had some unattractive deposits that I could successfully remove with ammonium thiosulfate, but after that it just looked very dull.
The Gordianus Pius was one of my first coins, I got it when I was about 12 years old. It had been in a cabinet during 20 years and instead of acquiring a nice toning it became dark brown and spotty. Both coins were not nice to look at with their previous toning. I assume that the new toning will look artificial for the moment, but the coins will continue to tone in the long term and I'm optimistic that the toning will be more even.

There are some youtube videos where they put the coins in a bag together with the cooked egg. That makes no sense to me. I think that the coins should be completely clean and not touch any of the egg, otherwise the toning will be uneven and the coins will get in contact with chloride and we really want to avoid that. I also think that the egg should not be too hot because we don't want too much steam and H2O. There will still be enough sulfur without any visible steam.

So, what I did:
1) I put both coins in acetone for a few minutes and later cleaned them with a cotton swab. If the surfaces are free from oil or any deposits the toning will be more even.
2) I cooked a scrambled egg
3) I put the egg in a bowl, then I put the coins in a kitchen strainer and left the strainer with the coins inside above the egg during 5min

I would never do this to any coins that were expensive or personally important to me. 

Here is the Julia Mamaea before I removed the deposits:
Mamaea1.jpg.2900820a68d4bc0ef09c76b8459e8983.jpg

And here are the results - please don't be too shocked:Bildschirm­foto 2023-06-17 um 18.13.14.png

I'm not sure if I regret this or not. Maybe I was a bit too curious... 

Edited by Salomons Cat
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2 hours ago, Salomons Cat said:

I tried the egg trick a few days ago. I didn't expect to post this here so unfortunately I only took photos after toning, not before.
There were some reasons why I tried it on these 2 coins. The Julia Mamaea had some unattractive deposits that I could successfully remove with ammonium thiosulfate, but after that it just looked very dull.
The Gordianus Pius was one of my first coins, I got it when I was about 12 years old. It had been in a cabinet during 20 years and instead of acquiring a nice toning it became dark brown and spotty. Both coins were not nice to look at with their previous toning. I assume that the new toning will look artificial for the moment, but the coins will continue to tone in the long term and I'm optimistic that the toning will be more even.

There are some youtube videos where they put the coins in a bag together with the cooked egg. That makes no sense to me. I think that the coins should be completely clean and not touch any of the egg, otherwise the toning will be uneven and the coins will get in contact with chloride and we really want to avoid that. I also think that the egg should not be too hot because we don't want too much steam and H2O. There will still be enough sulfur without any visible steam.

So, what I did:
1) I put both coins in acetone for a few minutes and later cleaned them with a cotton swab. If the surfaces are free from oil or any deposits the toning will be more even.
2) I cooked a scrambled egg
3) I put the egg in a bowl, then I put the coins in a kitchen strainer and left the strainer with the coins inside above the egg during 5min

I would never do this to any coins that were expensive or personally important to me. 

Here is the Julia Mamaea before I removed the deposits:
Mamaea1.jpg.2900820a68d4bc0ef09c76b8459e8983.jpg

And here are the results - please don't be too shocked:Bildschirm­foto 2023-06-17 um 18.13.14.png

I'm not sure if I regret this or not. Maybe I was a bit too curious... 

Well at least they toned evenly. You got what you designed it to do 🤣

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I thought I'd share a coin that has been undergoing the "go slow" toning process.

Here's the coin photo from CNG, not the best quality, but it will provide a general impression of the color and surfaces, which are very shiny and slightly rough, especially on the reverse.  

Athens, new style tetradrachm, CNG eAuction 525.1 lot 206, 10-19-2022

AthensnewstyletetradrachmCNGeAuction525.1lot20610-19-20226-17-23.jpg.e66aaa8e49a4d12dfaf06e4912f4b523.jpg

Since receiving the coin in late October 2022, I've had it on a counter in the kitchen, so it was exposed to the elements there; humidity, whatever pollution is blowing in through the open sliding door nearby, and other elements, including some sulfur from cooking and my very bad breath.

So, here is the coin as of November 9, 2022.  It was basically very bright and silvery in appearance,  Both this and the next photo were taken in natural light without the aid of a flash.

Athens, new style tetradrachm, c. 165-42 BC, struck 106/5 BC,

Thompson 757d

16.73 grams

D-CameraAthensnewstyletetradrachmc.165-42BCstruck106-5BCThompson757d16.73gCNGeAuction525lot20611-9-22.jpg.47c0b706827292acb1a636c87b2f6f60.jpg

 

And here is the same coin photographed today.  Since the previous photo the coin was move to the bedroom, not far from the bathroom and shower.  I must add that lighting conditions are somewhat different this time of the year, compared to November, with the sun lower and less direct light coming through the skylight, so my photos tend to be somewhat brighter

D-CameraAthensnewstyletetradrachmc.165-42BCstruck106-5BCThompson757d16.73gCNGeAuction525lot2066-17-23.jpg.2ee992dbefe4681ec4192c82fb92e30a.jpg

 

For comparison here is the coin photo with flash:

D-CameraAthensnewstyletetradrachmflashc.165-42BCstruck106-5BCThompson757d16.73g6-17-23.jpg.d7670f511833970e0bad94a548f24bce.jpg

 

The color is turning yellowish brown, but due to the cleaning, the surfaces will always be very reflective, something that will remain permanent for this coin.  I'll keep this coin out until maybe October of this year, then into a safety flip it goes.

 

 

 

 

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Many years ago in the age of commonplace smoking indoors, I bought, as a Junior , a very shiny British Crown. An advanced collector who was a dealer said I could put it in a brown manilla envelope for a few years and it would tone down nicely enough to remove obvious cleaning, or I could put it on the curtain pelmet,  dado or picture rail. In older British houses there is a wooden rail about 12 inches below the ceiling.  My mentor said this would do the same thing but it would happen but much more quickly. 

Both my parents smoked as did my grandparents which was the reason I never took it up. I tried it and it worked perfectly.

Recently I tried the egg trick on a Morgan Dollar that had arrived in a batch and was cleaned to beyond and back. I boiled an egg, mashed it and put it in a Tupperware box and let it cool. I then laid the Morgan Dollar on some Kleenex tissue paper on the other side of the box and a couple of days later there was a toned coin. I'm not sure if it would fool a third party grader but it was good enough for me to improve the look.

Last year at the FUN show I bought a Didius Julianus denarius I featured in another thread. It was a good buy but the dealer said he thought it had been artificially toned. I understand why he made the comment and it had been sold only 2 months before in the UK with a unsightly stain. I had passed on the coin myself at the auction. Looking at the original auction images the coin has clearly been "doctored" and will ever remain so if the Provenance is checked, but I was happy to obtain a "gap filler" a couple of hundred dollars less than I had expected to pay.

Therein lies the problem with artificial toning and that is future provenance........

From my perspective, collecting is not an investment and if my heirs sell at auction for prices more than I paid , great!  However if investment is an issue to you, then artificial toning is something to be wary about because there is now infinite possibilities to check a coins journey if it has entered the public auction forum.

I have a couple of "cleaned" English milled coins and would love to know how to get past a TPG detailed listing as their condition in respect of surface metal is great but clearly that was not good enough for some Bozo who wanted to see a bright coin. Any ideas would be most welcome.

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I tend to think there is no need for elaborate chemical tricks to get a nice tone. Just put them in a wooden tray and have some patience. This is how the “old cabinet tone” came about in old collections.

I was curious about the rate of toning for various species of wood trays and so I made some from several different types of wood. After a year they were all about the same with very little change in tone. The only one that showed any amount of noticeable change was oak. So if you are looking to speed up the toning process use an oak tray and check the coins every few months till you’re happy with the look. That would be my advice.

 

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5 hours ago, Salomons Cat said:

I tried the egg trick a few days ago.

So first of all, thank you - I have never seen this egg trick on a coin before. So it's a very interesting contribution! 

 

5 hours ago, Salomons Cat said:

And here are the results - please don't be too shocked:

I'm not sure what to think yet. I thought it would be a darker colour. Maybe like Parisian oxide or sulphur liver. 

But then again, I have to say - I've had Republican denarii with a blue/gold iridescent tint (ok you're missing a bit of the iridescent gold). But these coins with such a tint were extremely sought after. 

So I'm still a little unsure. I have already had similar tints (with gold) with Republicans and found them beautiful. On a late Roman coin a bit unusual for me. 

But interesting. I think for his 25 euro coins he can dare the experiment.

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1 hour ago, robinjojo said:

The color is turning yellowish brown, but due to the cleaning, the surfaces will always be very reflective, something that will remain permanent for this coin.  I'll keep this coin out until maybe October of this year, then into a safety flip it goes.

Cool... another very interesting experience report! Thanks for that.

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On 6/16/2023 at 12:25 PM, John Conduitt said:

That's to get the sulphur in a very short time. Technically it's artificial, but it would be exactly the same.

Yes. 
If you touch a mirror with your hands then you leave a fingerprint. That's because our skin is covered by a little bit of oil that protects us from drying out. The same happens when we touch a coin: We probably leave a fingerprint when we touch it, even if we cannot see it. I believe that this can have an impact on the toning of a coin in a long term. Maybe, if coins are evenly covered with skin oil that's not even a bad thing but also protects them... I don't know. However; when I get new silvers coins I often quickly put them in acetone first after I received them because I don't know how they have been handled in the past.
There is also one other thing: Our sweat contains chloride - very small amounts, but possibly enough to build tiny spots of AgCl (horn silver) on silver coins. Some people accept all of that on ancient coins, the aging is part of their natural charm and they have already been touched thousands of years ago anyways - without any precautions. So when collectors handle them, it might be completely neglectable.
But if you prefer a very even toning on a certain coin, then I believe that you can increase the likelihood if you carefully clean it with acetone and a cotton swab. The accelerated (or "artificial") toning further minimizes other influencing factors before the coin gets a layer of sulfur atoms because it only requires such a short time span.
So, the "artificial" (or accelerated) toning has it's advantages. It's just not very romantic. And I completely understand if many collectors don't want to do that. As I said, I wouldn't do that with coins that are important to me. It also cannot be undone without damaging the coin.

On 6/17/2023 at 11:31 PM, Prieure de Sion said:

So first of all, thank you - I have never seen this egg trick on a coin before. So it's a very interesting contribution! 

I'm happy that I could contribute something!

On 6/17/2023 at 11:31 PM, Prieure de Sion said:

I'm not sure what to think yet. I thought it would be a darker colour. Maybe like Parisian oxide or sulphur liver. 

In the meantime, I think that I prefer the egg toned versions of these two coins... At first I was also surprised by the strong colors and didn't know what to think. But now they look ok to me. The colors also depend a bit on the light. The previous photos were in bright daylight. But I took some other photos in the evening under artificial light. I must say that the colors are always quite strong, irrespective of the light and the angle or how I take the photo. But now, they seem a bit darker to me and the Julia Mamaea even has a bit of a golden tint. The Gordianus is just blue and violett, doesn't matter how I look at it.
By the way, I also found another photo of the Julia Mamaea before I cleaned it.

pre cleaning and egg toning 
image.png.83495435bb54722377475038fadb51c3.png

post egg toning:
image.jpeg.11560873ebd7c4f9ac83e66c920b151a.jpeg

Edited by Salomons Cat
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I got the two copies to look at - but "live" in real life in the hand, both don't look as bad as in the pictures, I think. I immediately took the coins and recorded two small videos as usual and uploaded them to my channel. You can see for yourself.

But I think you don't have to do anything, maybe just let them age naturally in the air and that's it. No experiments. I find both coins extremely beautiful - now that I hold them in my hand, I wouldn't do any experiments.

 

Gordianus III, RIC 34, Date 240 AD, Silver Antoninianus Rome, Aequitas

 

Gordianus III, RIC 202, Date 238-239 AD, Silver Antoninianus Rome, Victory

 

 

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