Restoring old coins
January 18, 2008 4:45 PM   Subscribe

I have a coin collection that has sat untouched for 50-60 years. At the time they were collected the coins were taken from circulation. They are from all over the world (no U.S. coins) and were minted in the early part of the last century. They were mounted on light cardboard pages with scotch tape. As you can imaging the tape has gotten quite brittle and sticky by now and may have interacted with the metal in the coins. I need advice on cleaning and restoring the coins in my collection. I understand that under normal conditions collectible old coins should not be cleaned.
posted by retiree to Sports, Hobbies, & Recreation (8 answers total)
You might want to run them by a local coin shop to see if you've got anything valuable. If you do, they'll be able to advise you on how to properly clean them. They may even be able to do it for you.

If you really don't care about their numismatic value and just want some shiny coins, vinegar should do the trick.

You should at least stop by the coin shop and buy a world coin price guide to see what you've got before cleaning them. Once you've cleaned a coin it normally loses nearly all its numismatic value.
posted by lairc at 6:00 PM on January 18, 2008

Seconding lairc; don't do anything before you either take them, in their current condition, down to a few coin shops for evaluation and advice, or buy a price-reference guide and look them up.

I'm not sure that any cleaning is a good idea on truly valuable coins.

This article suggests warm water and a tiny bit of dish soap if you really need to clean coins (e.g., circulated coins prior to storage). But I'm not sure I'd even go that route without having a firm idea if what yours are worth.
posted by Kadin2048 at 6:25 PM on January 18, 2008

I've never heard that cleaning coins makes them lose value. If you have an old coin that's already in mint condition, why would it be worth more dirty? I'm not snarking, I'm genuinely curious.
posted by pieoverdone at 6:42 PM on January 18, 2008

pieoverdone, I was curious about this too & found this in the section linked to above:

With the exception of freshly dug-up detector finds, cleaning or polishing your coins will do more harm than good. Once metal has been exposed to the air, it is natural for it to oxidize, or tone. If you strip the coin of this toning, not only will you lose any remaining mint luster, the coin will appear harsh and unappealing, and suffer microscopic abrasions that lower its grade. Plus, toned coins are worth more than stripped coins.
posted by hgws at 7:14 PM on January 18, 2008

WD40 is a good sticky-remover, and shouldn't harm metal. Don't take my word for it though.
posted by gjc at 8:15 PM on January 18, 2008

If you have an old coin that's already in mint condition, why would it be worth more dirty? I'm not snarking, I'm genuinely curious.

I'm no expert on numismatics, but just having read a little on the topic, I think there's a big difference between a "mint" coin -- one that's old and clean because it's never been circulated -- and one that's been circulated and has acquired a certain patina, but has then been cleaned. It's an issue, I think, of authenticity.

This is consistent with many other types of antiques (e.g. furniture and firearms); the ideal item is one that's both old and in perfect, as-new condition. But an item that's old and looks old is nearly always superior to one that's old but has been recently refinished or otherwise altered to look new.

Plus, I think many cleaning processes (abrasives, caustic chemicals, etc.) are considered destructive to the coins themselves. You're getting the gunk off, sure, but also destroying the coin a little bit itself.
posted by Kadin2048 at 9:13 PM on January 18, 2008

Talk to a coin dealer, not necessarily one who will buy your coins. It is my understanding that except for very, very old coins, anything that has been in circulation has quite low value. Certainly talk to one prior to attempting any cleaning etc.
posted by caddis at 9:32 PM on January 18, 2008

I've never heard that cleaning coins makes them lose value.

That's strange, because it's pretty standard advice in the coin collecting world to avoid cleaning coins, because cleaning *almost always* lowers their value:

The first rule of coin cleaning is: If you don't know its value, don't clean it, or if you think it is valuable, don't clean it, or if you know it is valuable, don't clean it. In other words, do not clean your discovered coins; leave them untouched and stored in proper holders. The reason for this is that coin dealers and collectors are interested in purchasing coins in their original condition and natural state of preservation.

retiree, you don't say whether you're looking to sell them, but even if you're not, you should take lairc's advice and show the coins to a few professionals before using WD40 (or anything else) on them. As counter-intuitive as it might seem at first, the coins are probably worth more in their current condition, tape and all, than they will be after you do whatever you do to "clean" them up.
posted by mediareport at 9:34 PM on January 18, 2008 [1 favorite]

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