Non-abrazing coin cleaning/saving

[BKB]

Now, normally someone would see this topic, and would start screaming that coins should not be cleaned or even touched in that way... However,sometimes you get a copper coin, and it has that green crust or reddish dust on it. Do you know, that this stuff can just eat the coin alive, and can even infect other coppers in your collection? Believe you or not, that green corrosion is contagious...

 

Now, what do you do? The best way, of course, is not to buy coins with that stuff on. However, I have seen a lot of coins on this forum that sport that green stuff. If you buy on ebay, Photoshop can do wonderful things to photos. Or, sometimes, I can't let a rare or scarce coin slip away... Then you get it, and start scratching your head(or, at least, I do.)

 

What to do if you already bought one with that green stuff on? Is there any interest in a thread like this? Would anyone like to share their experience in getting rid of green or reddish corrosion found on Russian coppers? Maybe, a way to get rid of that godawful sulfur stuff used by some to create fake patina on Russian silver coins? Or, how to get rid of iron rust on copper or silver coins (from that metal can they were hidden in for 100 years...)

 

My example:

 

Before:

 

 

 

The true color of the green was a bit darker.

 

 

After:

 

 

It does not always come out this nice (the coin is a few shades darker than the photo and there is some red under the brown), but it usually largely depends on how deep the corrosion is. This time it is was reasonably surface, with only a small area affected. There is some pitting, but it is better than before. At least I think so, and, the main thing is, -- the coin is hopefully safe now. There are a few spots left, but if they do not grow, I will leave them alone.

 

Anyone care to share the result of their experiments?

[bobh]

Good job!

 

You didn't say how you did it -- I usually put them in olive oil (extra vergine) for a month or two. Sometimes I change the oil and let it soak another several weeks if necessary.

 

I don't know exactly how the oil works, but I assume that the organic crud is dissolved by the oil and the green stuff is dissolved by the acid content of the oil. Extra vergine olive oil is best because it has much less acid than the cheaper kinds. Of course, the desirable brown patina is also affected by the oil, but to a lesser degree.

 

Somewhere I had a "before" and "after" of a copper 2k of Alexander I here on the forum ...

[BKB]

I am going to write that when I come back home. Did not know whether there was any interest...

[bill]

A good review of the problem can be found at this location. Find the Bronze Disease pdf about half way down the table.

[bobh]

Before:

 

 

After:

 

[BKB]

Read that article on bronze decease -- wow. Too involved for me.

 

Let me recount all methods that I tried so far. That would be a good "Emanuel" on what not to do, and what can be done if you are brave :-) I am recounting 8 years of experimentation. I would not try it on expensive coins first.

 

1. Lemon Juice + salt. This was the first method I tried. Basically soak your coin in lemon juice with salt, and it will clean it. I want to kill the moron that advised me to do it. Result -- destroyed coin. No, it cleans everything, including the metals mixed into the copper. Leaves pitted copper surface. Lemon juice without salt did not destroy the coin, but also did not clean it.

 

2. Next came vinegar. Did not do anything. Do not know what that guy cleaned with it, but the green remained.

 

3. Then came soaking in soap + water solution. great for dirt, but really feeds the corrosion. After that experiment I tried to keep it away from water for a while.

 

4. Then came soaking it in olive oil. Even after months, I found it not very effective. First, after the olive oil softens the green crust, you need to manually clean it off. The process needs to be repeated. It is hard to get the green stuff out of the pores and cavities. I hate any mechanical cleaning, so I stayed away from it.

 

5. Next came the electrolysis. I read about it on some antique coin forum. Tried it. Would not do it again. Only ones I succeeded to clean a coin, which was covered in black crust with some iron oxide inclusions. During electrolysis process in saline solution, the stuff just popped off. Involves water, so it is not a good idea to submerge coin afflicted by that green corrosion...

 

6. Next I tried boiling in olive oil. Not bad, if you can stand the smoke and can get the oil hot enough.

 

7. Next I tried boiling the coin in water with baking soda. The best way to get rid of the green stuff! Kills all patina. Coin becomes pink like baby's ass. I guess, the patina will return in 100 years...

 

8. This coin was cleaned like so:

 

a. soaked it in olive oil for 2 weeks, then

b. boiled it in water with baking soda.

 

Miraculously, the patina remained, and the green stuff is gone. Maybe the olive oil not only softened the crust, but also protected the patina somehow? I do not know.

[gxseries]

Might want to give verdicare a go BKB. Please try it on cheaper coins first before trying on more expensive ones!

 

http://www.coincommunity.com/forum/topic.asp?TOPIC_ID=62434

[bobh]

Might want to give verdicare a go BKB. Please try it on cheaper coins first before trying on more expensive ones!

 

http://www.coincommunity.com/forum/topic.asp?TOPIC_ID=62434

Strange -- none of the coins shown in that link seem to have verdigris, but other kind of dirt or dark corrosion of some kind. And with a few of them, I can't tell the difference in the before & after pictures.

[gxseries]

Bob, try page 3.

 

Again, I want to try this product but I have trouble getting it sent to Australia. It's not right for me to recommend a product that I personally haven't even tested but seeing the reviews, I thought I might as well give it a note. The most important thing is, it should remove a bit of verdigris BUT at the same time, NOT strip the patina which ruins everything.

[BKB]

Bob, try page 3.

 

Again, I want to try this product but I have trouble getting it sent to Australia. It's not right for me to recommend a product that I personally haven't even tested but seeing the reviews, I thought I might as well give it a note. The most important thing is, it should remove a bit of verdigris BUT at the same time, NOT strip the patina which ruins everything.

 

The idea is not to remove a BIT of verdigris, but to remove all of it, if that what you call it. Looked at that link -- it may be a good conservation technique (cannot tell from the photos), and a dirt cleaner. But, where did you see that green stuff on those coins? I want to see him try it on what I had to work with...

 

I am sticking to my method. I do not know what is in that chemical concoction of his and how it will react with an 18 century copper alloy. There is this stuff called MS70. Tried it on a bronze soviet coin ones -- turned the coin green and blue on contact. I do not know what he has against oil, and how he says that oil is agressive. I just bought a 1791 5 kop Paul overstrike that is rather black. Had it in oil for a month. Did not change color one bit. Still black and ugly. All I wanted is to get rid of light green corrosion, and to lighten the color a few shades, so I do not have to tilt the coin to see the eagle.

 

 

 

As you can see, the oil also did nothing to the green stuff - would have to remove it manually. The only logical next step I see is boiling it. However, from the way the surface looks, I can tell that it will do nothing except getting rid of the green stuff. However, I know of no other way to revive this coin...

 

As to mailing the stuff to Australia. Get someone here to purchase it, if it is commercially available, and then mail it to you...

[gxseries]

BKB - I had my fair share of this ugly verdigris with Russian copper coins and I know too well what it's like. It's just unfortunate that the more you try to deal with it, it seems to leave ugly pockmarks. I wasted a couple of nice overstruck coins over that. I think it is more undesirable unless you are happy with that.

 

The secret ingredient of olive oil is that it is slightly acidic and that is why it seems to be able to remove verdigris bit by bit. I would rather see a coin being conserved over a period of time instead of the patina stripped within mere seconds. Ruins value dramatically at the same time.

 

Congradulation with the 1791 5 kopek. Looks like the mintmark is large size as well. I like it!

 

I'm actually happy to experiment with verdicare and give it a go with what happens with 18th century Russian copper coins. I have no reply from anyone regarding about sending liquids overseas especially with the dumb scare over sending possible concoction of liquids becoming explosive.

[BKB]

Somehow, with the 2 kop, I was able to retain the original patina. With an overstrike -- there is no patina -- just ugly black and green stuff. I live easier with caverns, because I know that the green stuff will eventually eat the coin alive.

 

The only raeson I bought the overstrike was because it was cheap (about $200). Not too many interesting coins you can buy now under $1000. In the condition it is in, I do not really care about the size of the mintmark, - cannot put it in my collection anyway...

[bill]

I think several issues are being conflated in this discussion. It started with the growth of a green substance on a copper/bronze coin, a growth that is contagious. That growth is known as bronze disease and is a chemical reaction that does spread to other coins. It requires moisture to progress. Super heating the coin will stop its progress, but discolor the coin. It does not stop the disease, as it will start reacting again when moisture is present. The processes referred to in the link are chemical processes to neutralize the chemical reaction. There is no way to avoid pitting or other damage since the chemical process has already started to break down the copper when it becomes visible. Neutralizing the chemical process is the only way to stop its spread and have a good shot at preventing its return (and spread to other coins). Since it has already produced a chemical breakdown of copper by the time it becomes visible, damage has already occurred.

 

The other branch of the conversation seems to deal with "dirt" and "patina." Dirt can be removed without pitting or other serious damage to the coin. Patinas have already formed a reaction with the coin's surface, so removing a patina will necessary create some damage, even if its not readily apparent. Dirt and patina can be removed or left in place and not threaten your other coins. Bronze disease, on the other hand, needs to be dealt with immediately or the coin isolated from the rest of your collection.

[one-kuna]

I think several issues are being conflated in this discussion. It started with the growth of a green substance on a copper/bronze coin, a growth that is contagious. That growth is known as bronze disease and is a chemical reaction that does spread to other coins. It requires moisture to progress. Super heating the coin will stop its progress, but discolor the coin. It does not stop the disease, as it will start reacting again when moisture is present. The processes referred to in the link are chemical processes to neutralize the chemical reaction. There is no way to avoid pitting or other damage since the chemical process has already started to break down the copper when it becomes visible. Neutralizing the chemical process is the only way to stop its spread and have a good shot at preventing its return (and spread to other coins). Since it has already produced a chemical breakdown of copper by the time it becomes visible, damage has already occurred.

 

The other branch of the conversation seems to deal with "dirt" and "patina." Dirt can be removed without pitting or other serious damage to the coin. Patinas have already formed a reaction with the coin's surface, so removing a patina will necessary create some damage, even if its not readily apparent. Dirt and patina can be removed or left in place and not threaten your other coins. Bronze disease, on the other hand, needs to be dealt with immediately or the coin isolated from the rest of your collection.

Thank you, very clear explained.

I can't hide my curiocity but could you share if you have tried to clean coins on your own and have you had succesuful results, thanks again

 

P.S. I am using oil so far with no success.

[bill]

Thank you, very clear explained.

I can't hide my curiocity but could you share if you have tried to clean coins on your own and have you had succesuful results, thanks again

 

P.S. I am using oil so far with no success.

 

I generally don't clean coins. I will use an alcohol rinse followed by distilled water if a coin/token/medal is "greasy". I have experimented with olive oil on corroded tokens with good effect. The color comes out too bright, but I'm talking about heavily corroded tokens with the detail obscured. Vinegar works on real bad pieces, alternating with olive oil. I've used vinegar to remove "white crust" from a medieval coin, but that was a quick dip and rinse with distilled water. Too long and it would have had a negative effect on the coin. The crust was removed in less than 10 seconds. In general, I don't experiment on anything other that a real junker (the medieval piece was an exception, but I got tired of its appearance). I will sometimes buy a junker copy of something I own to see what effect the techniques have on them. I've never been willing to move from the junker to my good piece.

 

So I stick to alcohol and distilled water to remove dirt. Anything else does effect the surface of the piece. The corroded pieces I have experimented with came in lots that I bought for other pieces and I was trying to see what I could salvage. Harsher techniques work, but they do alter the appearance.

 

Bad chunks of dirt can be loosened with a toothpick in alcohol, but its risky. One slip and you can scratch the surface.

[bobh]

Bob, try page 3.

OK, I looked at the first five pages. The before and after pictures show minimal improvement, if any. Nothing compared to what BKB has shown, and what is a common problem with Russian copper from this period.

 

I think olive oil is better than its reputation, but BKB is right when he says it sometimes takes several soaks in order to get it off. It also isn't the best procedure for every coin; I have had best results when there is only a very little amount of green. Besides, once the green is off, you might not like what is underneath the green (usually heavy pitting, lamination or other damage)! And if the green stuff is too heavy, by the time the oil has done its job, most of the desirable brown patina will also have been dissolved away. Might as well boil the coin (or whatever...)

 

Also, I don't believe that bronze "disease" is contagious, but the fact that other coins might show similar symptoms is merely the result of inadequate storage and environmental conditions.

[one-kuna]

May be russian copper coins have a secret content added to the copper

 

I must share the story dedicated to my history school teacher recently passed away.

So, he said: when russians were involved in WWII, there were orders from russian government to the all soviet scientists to make a steel for tank T-34 more resistable against shoting.

So, once at one ceremony, where high government officials were present during boiling steel, one talant (old) man started sing "international" and look at the top on the wall where the Stalin portrait was and everyone supported him. Before that he ordered earliar to deliver few boxes of wax candles to him and place them right before the lab stow where the new kind of steel was prepared to be boiled. While singing and looking as everyone else to Stalin, he was breaking wax candles and throwing them to the stowe. One from the official accidently noticed that and there were no more secret what to add to the steeel to be more resistable for a tank. The new kind of steel was succefullly tested later and that is how T-34 was very succeful tank in WWII.

 

Can be above related to russian copper so something was added we do not know yet

[BKB]

May be russian copper coins have a secret content added to the copper

 

Maybe ear wax?

 

P.S. Nice story, but, what relation it has to the present discussion I am yet to understand. Please enlighten.

[BKB]

I've used vinegar to remove "white crust" from a medieval coin, but that was a quick dip and rinse with distilled water. Too long and it would have had a negative effect on the coin. The crust was removed in less than 10 seconds.

 

 

Was that a copper coin? What white crust?! This affliction I have not seen yet...

[one-kuna]

Maybe ear wax?

 

P.S. Nice story, but, what relation it has to the present discussion I am yet to understand. Please enlighten.

thank you for your word

[bill]

Was that a copper coin? What white crust?! This affliction I have not seen yet...

 

The question was whether I ever cleaned coins. The medieval coin was a billion coin, not copper.

[bill]

 

 

Also, I don't believe that bronze "disease" is contagious, but the fact that other coins might show similar symptoms is merely the result of inadequate storage and environmental conditions.

 

That is the definition of contagious in this case. If you have a coin undergoing a chemical reaction, those chemicals are in the atmosphere and any other coins with similar compositions can be attacked by the chemicals, i.e. the chemical reaction will spread from coin to coin. The spread assumes a closed environment (i.e. storage and environmental conditions). The environment may not cause the condition, but if you introduce the condition via a "sick" coin, it can spread if the conditions support the chemical reaction that is present on the coin.

[BKB]

The question was whether I ever cleaned coins. The medieval coin was a billion coin, not copper.

 

I apologize if my questions sounded abrupt. Did not mean for that. I was surprised to hear about white corrosion -- never saw it on copper. On silver and billon, yes. I guess that is what the vinegar is used... I tried it on copper with no success. Thank you for your response.

[bill]

I apologize if my questions sounded abrupt. Did not mean for that. I was surprised to hear about white corrosion -- never saw it on copper. On silver and billon, yes. I guess that is what the vinegar is used... I tried it on copper with no success. Thank you for your response.

 

No apology required. I didn't take it as abrupt. Shorthand in typing is not the same as a verbal conversation. Too easy to read in other meanings, so I try not to. Doesn't always work, but I try not to.

[alexbq2]

Let me just begin by saying that I don't know chemistry. But I think I read somewhere at some point that hydrogen peroxide can be used. I've actually tried it. Bubbles form around the coin. After a few hours the green stuff changes. Sometimes it flakes off, sometimes it changes color. It becomes sort of dark, maybe even black, but sometimes it is lighter. If you then soak it in oil, these new rust cuds can be flaked off with a toothpick.

 

I've experimented on a few coins. I am not in awe of the results, but I liked it better than just oil, or boiling in soda (which I tried once and will not do again).

 

Peroxide does not seem to affect the patina, but oil might. Also, I ended up buying a 30% solution. The 3% solution that you can get at your pharmacy was not always enough.