Please help, can this be saved?

Jsayre · January 4, 2009 5:15AM

Is there anything I can do to help this coin out with out losing it's skin completely? The green stuff is real thick, crusty and powdery. I belive it is a silver coin. Olive oil? I would rather leave it, than dip it in coin cleaner. I appreciate any help.

Preussen · January 4, 2009 6:14AM

Too bad; it has nice detail. Looks like it's pretty well gone to me, but you might try soaking it in acetone. And yes, it's silver. -Preussen

Edited to add: Vinegar might help, but I'm afraid the damage is irreversible

ASUtodd · January 4, 2009 6:21AM

Try acetone.... I mean what do you have to lose? The coin will keep getting worse if you don't try something. If you aren't worried about resale you can try an old trick that us metal detectorist use, peroxide.... I've heated peroxide up and then put coins it (that I dug) with great success. Again, acetone works well but with that much green goo on it.... you may have to get drastic.
Todd

IloiloKano · January 4, 2009 6:24AM

Since you think it is silver, perhaps that green stuff is the result of PVC contamination. IF that is the case, then acetone (short soak) should cause some of it to release, which would then give you confidence in getting more off with a longer soak, while rolling (not wiping) a cotton swab over the surface to pick up the PVC faster. Since acetone does not chemically react with metals, you can safely use it on coins without fear of damaging the metal, though long term heavy PVC contamination will result in pitting, and its removal will make the pitting more evident. On the other hand, acetone is extremely hard on living things, so if you use it, make sure you do so in a very well ventilated area. Though the fumes are harmful to humans, they aren't anywhere near as harmful as metholethylketone (MEK), which will clean just about everything.

If an acetone soak does not produce noticeable results, then I would doubt it is PVC contaminated, and I would lean towards it being something like the verdigris to which bronze and coppers are susceptable, and I would then recommend a very long term soak in olive oil, since that process would take much much longer to remove such an extreme build up as your coin exhibits.

More than likely others will offer better and more knowlegeable advice.

Good luck.

crito · January 4, 2009 6:26AM

Leave it alone. There's a good chance half the lettering will come off with the green stuff.

spoon · January 4, 2009 6:42AM

That looks like hard verdigris, not PVC residue - the sort of stuff that doesn't come off without taking half the coin with it. You can try a long acetone soak and then olive oil to see how much, if any, does come off. But I think that stuff's there to stay.

1jester · January 5, 2009 3:43AM

Looks like verdigris to me, too. Short of chemically stripping and/or scraping it, I don't see that stuff coming off.

zeebob · January 5, 2009 4:26AM

If you like the coin and want to prevent future damage, send it to NCS. Once the green stuff comes off, they'll dip it for you. I don't see this coin ever coming out attractive. But NCS will get the gunk off and passivate the surface so future corrosion is less likely.

ajaan · January 5, 2009 4:31AM

NCS isn't cheap. Is the coin valuable?

zeebob · January 5, 2009 8:38AM

Sorry, let me clarify my statement about NCS. It will run a bit of money.

I assume the coin is of value to the OP since he (or she) declared they would, "rather leave it, than dip it in a coin cleaner." I read that as, "the coin has some historic or sentimental value to me and I would rather not destroy the coin's surface any further." Perhaps I read too much into the OP.

I actually have no idea about the monitary value of the coin. I only suggest NCS if the OP wants to protect the coin from further corrosion (the green bits look like active corrosion to me), but doesn't want to experiment and maybe further damage the coin's already crusty surfaces.

I've paid NCS, NGC and PCGS to perform work in some cases just because I wanted the finished product no necessarly because it made good economic sense.

I'm interested in the answer to Ajaan's question too. What is the monitary value of the piece?

Jsayre · January 5, 2009 10:11AM

I am not really positive on the value of this coin Maybe 20$-30$? I am not really worried about the price I just like it, but not enough to send to NCS. It is in olive oil right now and I will certainly update everyone with pics. I did not think that verdigris would form on silver, but it is exactly what it looks like. I do not think that this coin has ever seen a form of PVC. Thanks for the advice everyone.

Sapyx · January 5, 2009 10:17AM

Prussia 1/3 thaler 1758, KM# 285 I believe. silver content reported at .666 fine. CV $120 in my 2002 edition Krause.

I'd suggest sending it to NCS if you think it's worth it, or "conserving" it yourself if not. You'll need some kind of reactive chemical to remove the green; I don't think acetone will do it; that's far too deep to be simple PVC deposits.

I'd treat it as if it were a metal detecting find (which it probably is). Some remedies from the ancients collectors over on FORVM:

- vinegar
- ammonia
- lemon juice and sodium bicarbonate, with a piece of tin foil

Whatever happens, the green has most likely come from the copper in the coin, so the surface will probably be damaged no matter what.

Jsayre · January 5, 2009 10:40AM

Thanks for the info. I was thinking the verdigris may have been chewing on what little copper may be in the coin. 120$!! Yeesh maybe I should conserve it.

PHILIPPINECOINEXPERT · January 5, 2009 6:12PM

I KNOW I MIGHT CATCH SOME FLAK FOR THIS, BUT TO ME, THIS IS AN OBVIOUS CANDIDATE FOR THE OLD BAKING SODA TREATMENT. BAKING SODA IS SOFTER THAN SILVER, BUT HARDER THAN MOST TYPES OF CRUD FOUND ON COINS. IT WILL NOT LEAVE SCRATCHES OR HAIRLINES ON THE COIN, BUT IT WILL LEAVE IT WITH A RATHER UN-NATURAL SHINY APPEARANCE. IT WILL, AT LEAST, BE VERY CLEAN AND MUCH PRETTIER.
JUST MAKE A PASTE OF SODIUM BICARBONATE AND WATER, AND RUB HEAVILY WITH COTTON BALLS. OBVIOUSLY, NOT A GOOD IDEA WITH ANYTHING NEAR MS, OR ANYTHING WITH A DECENT PATINA, BUT WORKS WONDERS ON UGLY DUCKLINGS.
MANY SEA SALVAGED SILVER COINS WERE DONE JUST THIS WAY IN THE 1960'S, AND STILL TRADE WITHOUT UNDUE RIDICULE.

Please help, can this be saved?

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