[Update - 5-11-06] tiny green spots on copper/bronze coins

secondrepublic

I just bought a bronze coin with a few tiny green spots on one side. It seems too small to be PVC - though I guess anything is possible. I remember some discussion of this a while back. What could it be? And is there anything that can be done about it?

rhound1977

You can try Konsolve or Acetone dip, that my help, but not sure....

Aethelred

In many ways copper is like a living thing, no two copper coins are just alike, they will age with time and they can get sick. It sounds like your coin is sick. I would try treating it with acetone.

secondrepublic

Is acetone okay for copper/bronze coins?

This is kind of an expensive piece... I might need to do some testing on cheaper pieces first.

What about if it's verdigris?

Aethelred

The acetone will not have any impact on the toning, luster or metal, but it will remove any oil based gunk and it should neutralize any growing spots.

21Walker

I'm with Aethelred,. Cacth it now before it damages the metal. make sure to use distilled water on the rinse........have fun, but get it early......Rick

MacCrimmon

<< <i>I'm with Aethelred,. Cacth it now before it damages the metal. make sure to use distilled water on the rinse........have fun, but get it early......Rick >>




I'm afraid water is only a potential catalyst for further problems down the road. I'm asking one of our members for permission to post a PM regarding mineral oil, etc.

That said, I have used a xylene soak and soft Q-tip to "nudge" soft verdigris from an AU copper coin before. It will either work or it will not...... more later.

secondrepublic

Part of what makes me nervous is that the coin is really nice BU... mostly original red on the side with the little green dots. I am leaning toward sending it to NCS rather than doing it myself. Anyone have any experience using them for UNC copper/bronze?

ajaan

I have had zero luck removing tiny green spots off copper/bronze coins. If it is a valuable coin, I wouldn't even try, I would send it to NCS.

Aethelred

If you dip the coin in acetone there is no need to rinse it, the acetone will dry very rapidly and leave no residue

spoon

<< <i>I have had zero luck removing tiny green spots off copper/bronze coins. If it is a valuable coin, I wouldn't even try, I would send it to NCS. >>

Agreed! If you think the green stuff may indeed be hazardous to the coin's surface, give NCS a try. But, though acetone is generally 100% safe, I wouldn't want to risk it with a scarce or valuable coin unless it's obviously harmful, dripping PVC residue. Perhaps it was user error, but I have had minor noticable changes in luster and tone on bronze after an acetone bath.

secondrepublic

Do you think there's a need to get rid of those tiny green spots?

Or should I just send it to NCS and let them worry about it?

MacCrimmon

Following is several PMs between myself and our esteemed oreville:


Date Posted: Jan/23/2006 1:21 PM
Hi Robert,

I've seen you mention this mineral oil umpteen times; what gives?

Are you submerging the coppers into the MO, or just coating them with it.

You mentioned MO vs. Intercept; running an experiment?

Is this an old Norweb secret? How in the world do you get the MO off of the copper when it's ready to slab? Acetone; xylene?

All very interesting.

Regards,

Doug


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Date Posted: Jan/23/2006 1:58 PM

Doug:

Not a coating. A complete submerge in the mineral oil. Akin to using a vacuum to suck the air out of the container that the coin sits in.

Try it. Take a few red cents from your pocket change and put them in a very small bowl of mineral oil which can be reused only for this project. The odorless colorless kind.

Then take them out and squeeze dry them by using your thumb and forefinger and soft tissue paper on both sides of the coin at the same time. No rubbing. You will see that the mineral oil disappears right off the coin after using different areas of the tissue paper to do it at least 4 times.

I have kept the red copper coins sitting in the mineral oil as a permanent bath. For decades or more.

In reality all the mineral oil does is keep the bad air out. Changing the mineral oil every year, then every few years is necessary as the oil will possibly become more polluted.

But you will see that bad air will not come into contact with a hard plastic 2x2 I like the nickel sized ones as they hold more oil or the cent plastic tube of 45 or so cents.

When I store an entire roll of cents, I make sure that the tube of cents has the level of mineral oil sitting higher than the last cent that was put into the tube. Of course, the tube must have at least 1/4 inch of oil to start with before putting in the first coin. The each coin goes in one at a time. The oil also prevents the cents from "banging" into each other! As you get very close to the top of the roll, you will note that you need less and less surplus oil over the last coin in the tube as you can control the placement of the coin into the roll. Once the roll cap is sealed, you then wipe dry and seal the cap in with some good plastic tape to keep from opening. Check once a year and change the oil by dumping the coins back into a ceramic bowl and flushing with new oil. It does get messy but the mineral oil is very cheap.

Also very time consuming.

Much better than olive oil as mineral oil does not get rancid.

Now mineral oil can actually improve the appearance of some red brown cents by bringing them back to red or almost all red as the oil does seems to get "under" the toning and separate it from the copper surface. But this works only when the toning is very minimal.

The oils are also used as a coating by members of the EAC to give brown copper cents that "glossy" look. That is ok with me also but the danger is that the mineral oil (more so for olive oil) can darken the brown copper cents to a darker brown.

Robert


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Date Posted: Jan/23/2006 2:03 PM

Doug: It was a practice used by many collectors of copper coins in New York City, Philadephia and Baltimore back in the 1930's through the 1960's as the air in the major industrial cities on the east coast was so bad that using the mineral oil was the only way to keep the air of the red copper coins.

I bought rolls of BU red cents starting around 1966 that went back to the 1920's and 1930's that had been sitting in oil for over 30 years!!

The original tubes were made out of GLASS which is better than the plastic used today!!!

Best,

Robert


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Doug: If the coin is pristine red BU, you do not need acetone to rinse it off. Why? The oils literally is easy to be absorbed from the smooth perfect surfaces of the mint state cents.

Circulated coins will probably need acetone but even then, I prefer not to use it. Eventually, enough sqeezing of the coin will extract 99%+ of the oils from the circulated coin.

Keep in mind that when you put your hand in a fresh bag of BU cents in a mint bag you can actually feel the machine oils all over the cents in parts of the bag.

The machine working parts around the dies are kept lubricated with machine oils so that in fact, the coins are born with oil on their surfaces.

Prior to the 1980's, working dies were also routinely lightly lubricated (coated) with oils to keep them from rusting or sticking to the planchets when striking and discharging. A even more common thing in the 19th century in which the dies were also put inside vats of lard for months at a time to keep them from rusting!

So the coins were born with oils!!!

Best,

Robert


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2ndRP, the highlighted part might cause the 'lifting' you need. Another thought is that "grime" (industrial pollutants which may be dulling the coins lustre, be it cu-ni or bronze coins; even silver) may aid in naturally and non-invasively restoring the coins surfaces. But I would not advise trying on any coin of value.

Certainly NCS could render an opinion as to proceed, but I believe they no longer guarantee an "oops" if the coin turns out badly.


Good luck.

Cheers,

Mac

Steve27

If it's verdigris then learn to live with it (I doubt that even NCS can remove it). If it's PVC then try acetone, it's very easy to use and harmless to your coin. Got pics?

secondrepublic

Here is the coin:

Linky linky

The green spots are under the "R", just above the middle of the bottom swoosh of the "S", and on the "Z" where the top of the Z is pointing southwest like an arrow. The color is an intense greenish-blue.

ccrdragon

you can try Acetone or mineral oil (let it soak for awhile), but I think your best bet would be NCS. Be aware that if it is verdigris and if it is advanced, removing the verdigris will leave surface blemishes (or worse, pits in the surface).

oreville

<< <i>our esteemed oreville.... >>



"Our esteemed oreville" ????? Hardly!

However, the mineral oil bath WILL help to dissolve as much of the outer layer of verdigris without leaving a coin that is pitted and scarred looking as the mineral oil does NOT "scrub" all the verdigris off the coin. You do NOT want to do that at this point since removing all green verdigris as ccrdragon posted may leave an ugly pitted/scarred surfaced coin.

Keep in mind that the odorless and scentfree mineral oil is very gentle on the coin, does not scrub verdigris away, only dissolves what can be removed without damaging the coin but do it for a very short time duration as the mineral bath can darken the copper coin a bit.

Once completed, squeeze dry the coin with your thumb and index finger and two or more layers of very soft fine quality tissue paper. Do NOT rub.

The acetone can be used to "rinse" the coin once 99% of the mineral oil is removed if you want but it is not absolutely necessary. Quite frankly, the mineral oil usually give the copper coin more "sheen" and "gloss" to it even when brown.

Steve27

I doubt anything will help the spot under the "R."

1jester

<< <i>I doubt anything will help the spot under the "R." >>



I agree; it's already developed. I've seen this on plenty of coppers, and it's some kind of verdigris contamination.



PS: Dear Esteemed Orville, thanks for your valuable comments and trade secrets!!

secondrepublic

Assuming I try this mineral oil method, how long should I do it for? And is it possible to get the mineral oil on only one side of the coin? (I don't want to soak both sides if it's not necessary.)

oreville

secondrepublic: Yes it is possible to do only one side only. But perhaps we should see pictures of the other side to see why you feel this way? Consistency in look of the coin suggests that using mineral oil on both sides is preferable to doing one side only.

I agree that the verdigris below the R is probably too difficult to remove but lets face it, we are looking at pictures and might be very shallow. Hard to tell for sure.

I suggest you practice on some brown and red-brown pocket copper cents (pre 1982) before doing it on this cent. Start by using a Q-tip and a very small very clean ceramic or glass bowl (small ashtray or even smaller sized). Pour the mineral oil into it first. Then dip the Q-tip into the mineral oil until soaking wet and dripping then dab the excess on one side of the coin to investigate what you have. Then repeat until you have a bubble of mineral oil on one side of the coin. The coin should sit on a very soft multi layer of tissue paper along with an extra layer of plastic saran wrap trimmed/cut around the coin then with more layers of soft tissue on top also cut around the coin. This is if you are looking to do one side only. Practice on red-brown copper cents (even post 1982 red-brown zinc cents is ok to do). Change the q-tips frequently and never redip the old q-tip into the fresh mineral oil.

Give it a shot practicing wise.

When ready to do the old coin which will not be for another few weeks (as you need the practice) you will then be ready on work on the old coin but not until after April 18th as I must finish up my tax season as a CPA first!!!

oreville

Speaking of which, where is Lordmarcovan?? He should be very excited about his recent mail!

shirohniichan

<< <i>Speaking of which, where is Lordmarcovan?? He should be very excited about his recent mail! >>



Good question.

I've been shocked to find some nice bronze pieces I have have developed green death. I guess I should go back to silver.

ajaan

LM has a new job where they don't allow computer use. He only has dial-up at home. At least that is what he told me a while back.

IlikeZARcoins

I have found two green spots on a slabbed gold coin. I didn't notice them until after I had bought them and looked at them with a magnifying glass. It is a coin I want to keep.

What caused these green spots on my gold coin ?

Will these spots spread ?

Is it a viable option to send the slab back to NGC to have them remove the spots and then reslab the coin ?

Any help is appreciated.

secondrepublic

<< <i>I have found two green spots on a slabbed gold coin. I didn't notice them until after I had bought them and looked at them with a magnifying glass. It is a coin I want to keep.

What caused these green spots on my gold coin ?

Will these spots spread ?

Is it a viable option to send the slab back to NGC to have them remove the spots and then reslab the coin ? >>



If your coin is in an NGC holder and is gold there's probably nothing to worry about. You could always send it to NCS - which is part of NGC - and see what they say.

Is it even possible for a gold coin to have verdigris on the surface, if the gold contains a little bit of copper? Someone else may have an answer.

secondrepublic

Update:

I chickened out in early April and sent the coin to NCS. Given the condition-rarity of it, I didn't want to experiment on it, even with all the great advice you guys gave me.

This morning I found out that not only had my coin been successfully conserved by NCS, but it was sent on to NGC for grading. (Which I did not request!). NGC graded it MS-64, and the coin is in the mail on its way back to me.

I mentioned that I hadn't requested the grading, and the person at NGC said they would refund me that charge.

Woo-Hoo!

1jester

Congrats!

oreville

secondrepublic: Congrats!