Silver coins in my lot of uncleaned

[Platon]

I'm new to cleaning coins and I believe I have found a few silver coins in my lot of uncleaned bronze roman coins.

The first coin I am fairly certain is silver. It is about 1cm in size and less than 1mm thin. It has what appears to be some kind of purple/blue-green patina but after soaking in distilled water for over a month and brushing it gently with a toothbrush distinct bright silver spots started to emerge.  The picture below shows it, it is either some kind of metal coin with a damaged patina or a dirty silver coin. I am not even sure if it is roman as nothing like it has shown up in my lots. I don't know what to do with it now.



A second coin I am not sure about. It has a crusty ugly blue/green patina like substance with a few red spots. It is hard to see in the picture below but after soaking in distilled water and light brushing faint shiny silverish spots are starting to emerge. Again I don't really know what to do, the coin looks rough but I've seen pretty crusty coins turn out good in this thread. I simply don't know if the blueish crusty stuff is infact patina or something on top of the silver that I should remove.



A third coin is the biggest mystery. I believe it might be a really low grade gold coin. Beneath some green and black crust there is a distinctly yellowish shiny substance. Under direct light it seems to shine like gold, atlhough it is very dirty still. The weirdest thing is that after taking it out of distilled water a white film comes very apparent on the entire back of the coin. On the front this film is only on a few patches. The picture below shows first the coin dry and second the coin wet -- both in the same lighting but with very distinct looks. The third frame shows the coin's other side with the white film only being a small patch.



Any help would be great! Also sorry for the poor image quality, I am currently camera-less. I did also find another silver coin in this lot and it cleaned easily although it was a thick crude slug with absolutely no detail.

[SRukke]

I'm new to cleaning coins and I believe I have found a few silver coins in my lot of uncleaned bronze roman coins.

The first coin I am fairly certain is silver. It is about 1cm in size and less than 1mm thin. It has what appears to be some kind of purple/blue-green patina but after soaking in distilled water for over a month and brushing it gently with a toothbrush distinct bright silver spots started to emerge.  The picture below shows it, it is either some kind of metal coin with a damaged patina or a dirty silver coin. I am not even sure if it is roman as nothing like it has shown up in my lots. I don't know what to do with it now.



A second coin I am not sure about. It has a crusty ugly blue/green patina like substance with a few red spots. It is hard to see in the picture below but after soaking in distilled water and light brushing faint shiny silverish spots are starting to emerge. Again I don't really know what to do, the coin looks rough but I've seen pretty crusty coins turn out good in this thread. I simply don't know if the blueish crusty stuff is infact patina or something on top of the silver that I should remove.



A third coin is the biggest mystery. I believe it might be a really low grade gold coin. Beneath some green and black crust there is a distinctly yellowish shiny substance. Under direct light it seems to shine like gold, atlhough it is very dirty still. The weirdest thing is that after taking it out of distilled water a white film comes very apparent on the entire back of the coin. On the front this film is only on a few patches. The picture below shows first the coin dry and second the coin wet -- both in the same lighting but with very distinct looks. The third frame shows the coin's other side with the white film only being a small patch.



Any help would be great! Also sorry for the poor image quality, I am currently camera-less. I did also find another silver coin in this lot and it cleaned easily although it was a thick crude slug with absolutely no detail.

Coin 1. can't tell by the pic but it really doesn't look silver. Your call.
Coin 2, certainly doesn't look silver???
Coin 3, gold doesn't tarnish and this definitely doesn't look like gold.

Just my opinions.

[Platon]

Not suprised by your reaction given the terrible photos. With coin 1 the metal beneath the greenish purple layer is bright as can be and looks just like silver. Not sure if this could be some other kind of metal? It does not look at all like copper or bronze.

With coin 2 the shiny quality is impossible to see in the photo. I am not certain if it is metal shining through damaged patina or possibly silver. The shiny metal doesn't have the orange/brown hue of copper or bronze. I could clean off more of the green substance to get a better look at the shiny stuff beneath but I am afraid that this would be a terrible idea.

With coin 3 I would be very suprised if it was indeed gold but of my 200~ uncleaned coins I have never seen something so yellowish and shiny. I've found that the white film layer can be chipped off so maybe I can get a better picture. I have seen damaged coins with copper or bronze showing through but nothing was this distinctly yellow.

[Platon]

Well for better or for worse I put the second coin in lemon juice for 3 minutes. Some of the crusted stuff on top came off easily revealing what is underneath. I believe it is a silvered coin. On the front of the coin it seems most of the silver has been lost over time, whereas on the back there seems to be a good amount of silver. This is all assuming the silver coloured metal I am seeing is in fact silver!

Not sure how to proceed with the first coin which seems quite delicate. I am not sure if I should clean off what is on top of the metal.

[ionutbd]

I go for „fouree” coins. So, be careful with scrubbing

[Platon]

Yes I will have to be careful indeed!

Here are much, much better photos. I am proceeding with caution although the obverse of the supposed fouree is going to be very tricky to do, I am worried about getting lemon juice onto the bronze parts. The second I haven't touched at all, I have no idea what it is, I don't even think it's roman.

[SC]

That top coin is a Roman Antoninianus from the 3rd quarter of the 3rd century.  It appears to be struck by Claudius II Gothicus AD 268 - 270.  It was technically a "silver" coin but in fact has a silver content in the 2 - 2.5% range.  Thus it is in effect a bronze coin.  However, it was given a silvery appearance through a process known as "pickling" or "blanching".  The silver was not added but was brought out of the body of the alloy at the surface via a chemical reaction.  Nevertheless, the silver at the surface is no longer part of the bronze alloy and is easy to unintentionally remove during cleaning.

On your coin I see dark green bronze poking through from under the silver, bright silver, lighter green encrustations that are over the silver, and red-brown cuprite that is related to these encrustations.

You can't do anything for the bronze, silver or cuprite.  (Though you could try to grind the cuprite down you may expose holes underneath.)

You may be able to remove the lighter green encrustations with the use of a sharp scalpel under magnification.  This may or may not remove the underlying silver depending on how stable that silver layer is. 

I have successfully removed the green encrustations from on top of the silver on 4th century silvered bronze coins and on Aureliani of Aurelianus and Probus but never on Antoniniani of Claudius Gothicus or Gallienus so I don't know how successful you might be.

You are right that the second coins is not Roman, it is medieval but I know nothing beyond that.  It does seem to be a fouree of a medieval silver penny but I don't know if that is even possible.

Shawn

[Platon]

thanks to both of you for the information! I would have never identified these myself. I will do my best to make the Claudius II coin presentable, hopefully without removing any of the silver.

[Augustin Caron]

Hello,
flaking, crystalized, almost broken or fragile silver can be (In a reversible way, acetone being the solvent) fixed by paraloid B72.
Horn silver can be stopped and fixed by Na2S2O3 (thiosulfate de sodium in french), then cleaning can be done by mechanical means (lightly pressing and pushing). Fixed zones are then easily (stay soft on pressure !) separated from "native" silver.
I think that no heavy mechanical way should be used on silver, which is a soft metal.
AC