Tips For Coin Restoration

When it comes to cleaning and restoring coins, the best advice is,

Our first impulse on finding something dirty is to clean it up. We polish the silverware, wash the car, and scrub the floor. And in each of these cases, cleaning restores the once soiled item to pristine condition. The same applies to old coins, right?


If numismatists - those expert in coin collecting and valuation - agree on one thing, it's that coins should never be cleaned. Every coin dealer has horror stories about a non-collector who comes into his shop with a box of shiny old coins. Most of the time, the coins have no numismatic (collector) value at all; they are just old but common coins. But occasionally, a rare former beauty is found in the mix. It's a former beauty because whatever value it once had has been scraped off by an excited finder and a jar of silver polish. The coin, which might have been worth hundreds or thousands of dollars, is now all but worthless.

But it's not just excited treasure hunters. Even archaeologists working with ancient coins come under fire for the practice of restoring ancient coins, although in their case it may be necessary in order to see the coin well enough to properly date and categorize it. Those coins will not end up in most collections. But then again, archaeologists are not trying to preserve numismatic value.

But why should a coin be any different from your car, which you want to keep looking shiny and new?

The difference is that non-gold coins begin to "tone" as soon as they are minted. That is, the metal on the surface interacts with oxygen in the air, resulting in a thin layer of discolored metal. In the case of silver coins, this toning can actually add value to the coin, as some coins tone with blue, red, or even rainbow colors that collectors find desirable. Copper coins tone as well, to differing shades of red or brown, and while they are not usually as pretty as toned silver coins, they acquire an aged and natural look that collectors expect. A nicely toned coin not only looks good (in the eyes of collectors), but the tone itself can act as a preservative, keeping the rest of the coin from undergoing a reaction to the air. Coins with a good tone should never be cleaned or polished.

Remember, collectors may want old coins, but they expect those coins to look old. The toning and discoloration on most coins adds to their value. Not cleaning filthy coins may detract a little from their value, but poorly cleaning them can result in a permanent loss of most of it.

However, they are your coins, and if you insist on cleaning them, here are some tips that can help you while minimizing the damage should you try to sell the coin someday.

The first rule is - no matter the coin - never use harsh abrasives like silver polish. Abrasives scrape the top layer off of whatever they are polishing, and in the case of a coin, that top layer contains all of its detail and hence its numismatic value. Polishing in this way will leave the surface of the coin covered with tiny pits and scratches, not exactly conducive to preserving the coin's value. If you clean the coin using an abrasive, you'll get a shiny coin, but it will not be a coin that collectors are interested in. To see for yourself, try it on a penny, especially one from before 1982 (when they were 95% copper). The coin will be shiny and clean, but if you compare it to a similar coin, you will see that it also looks "unnatural". Shiny, yes, but it will not look like it looked naturally when it was minted. Collectors eschew coins that don't look natural.

That's what not to do. Here's what you can do:

Coins are best cleaned with soap and a soft cloth or you can use Vaseline or olive oil and a Q-tip. These methods can remove dirt and grime while not scratching the surface. Because gold is inert, it does not tone when it comes in contact with oxygen and so a simple surface cleaning will not usually change the coin's appearance. Silver coins, including pre-1965 half dollars, quarters and dimes, will retain the same toning (good or bad), as this kind of cleaning does not remove the surface layer, but it may remove dirt, grime, and some oils from the surface of the coin.

Be especially careful not to push dirt around a coin's surface. Coins are generally made of soft metals, so anything harder than them (like small rocks) will leave scratches that can destroy the coin's value.

After cleaning, rinse the coin in distilled water. This will remove what your Q-tip dredged up without leaving residue on the coins.

After the rinse, you may pat (not rub) the coin dry with a soft cloth or use a blow dryer to dry it. Be sure to handle a coin on the edges, as the oils on your fingers can get on the coin and undo all the progress you've made.

Occasionally, someone will come up with a new (and usually "foolproof") method for coin restoration, whether dipping the coins in ketchup or vinegar or Coca-Cola. What these methods usually involve is dipping the coin in a very weak acid to "restore" the surface. Most of the time, they can ruin the toning (that's what acid does), causing a valuable coin to lose most of its value.

Whatever method you try, it's best to test it on a non-valuable coin of similar metal first. That way if a certain method does have bad effects, you'll find out before you ruin a valuable coin. I discovered this much to my chagrin when cleaning a batch of 1943 "steel" pennies in an acid solution. I'll never know if it would have worked, because I had the pennies in a galvanized steel container and the acid, combined with the galvanization, fused the pennies into one worthless chunk.

Lesson learned. If I have coins that I think might be improved with a good cleaning, I seek out an expert. The vast majority of the time, he tells me what I'm telling you: when it comes to cleaning coins, don't!

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