Expert: Ronald Fern - 2/3/2010

Question
Hi--since you were so helpful with your last answer, I thought I would ask you about this--I have a couple of albums of silver coins where the coins are starting to get discolored, some getting black around the edges--while other albums, right next to them, are fine, with no discoloration--do you know what causes this, and should I switch the coins out of the albums?  And how can I clean the coins without harming them?  Much thanks for any insights on this--Raymond

Answer
Hi Raymond:

Thanks for the second question. It's good to know that you found my answer to the last one helpful.

I don't recommend cleaning collector coins. Cleaning can destroy the numismatic value. You can do more harm than good. Even rubbing a coin with a very soft cloth can leave minute scratches on the surface that will adversely affect collector value. To improve a coin's appearance it sometimes is acceptable--on a very limited basis--to gently swish it in a diluted solution of pure soap, rinse with distilled water and allow to air dry.

Never use any type of commercial jewelry polish on coins. These compounds contain abrasive grit that will mar their surface, and if used often will eventually wear away the metal. The same advice goes for "home remedies" such as vinegar, lemon juice, tomato juice, etc.

There is usually no reason to clean a coin. Unless the substance is destroying the coin.

Do not try to clean COINS. If they have some goo on it, or acid or something reacting with the surface then Liquid dish soap and water will clean it enough. Or a neutral solvent(acetone) There is no way to clean Copper, Silver or Nickel that keeps the original luster and patina that only time gives them.

The OXIDATION that takes place on copper is caused by the environment they have been in. Sulfur, moisture, Oxygen and chemical out gassing from paint etc all change the luster of the coin. Some discoloration is expected on collector coins. In fact High Quality Coins are graded and priced according to their original coloring. Many collectors may pay a good deal more for a coin that has attractive toning. And any dealer or collector will only pay half (or less) for a cleaned specimen.

Below is an excerpt from a professional society (authorized by the US Congress) in reference to cleaning coins.:

" Rule number one of coin collecting is "DON'T CLEAN YOUR COINS." Improper cleaning will reduce the collector value of your coins by 50 percent or more, so don't clean your coins.

There are some very limited things you can do to improve a coin's appearance, but read these instructions very carefully. There are two basic forms of cleaning - Destructive Cleaning, and Nondestructive Cleaning.

Destructive cleaning involves two principal products - those that contain an abrasive, and those that contain an acid. Pencil erasers, Silver or Brass paste polishes ("Brasso"), emery cloth, sand paper and even your fingers represent the abrasive area.

Liquid silver cleaner, vinegar, tomato juice, lemon juice, the dips, and soft drinks all contain acids which will damage some, or most coins.

Safe to use as a nondestructive cleaner is a weak solution of pure soap (not detergent) and distilled water. This will remove surface soil, grease and oil, but even this should not be used on proof coins or upper grade copper alloy pieces. After using, rinse very thoroughly in distilled water and allow to air dry, or pat dry. DO NOT RUB. Even a soft cloth will pick up grit and scratch the coin surface, a dead giveaway that the coin has been cleaned.

Above all, avoid the home remedies. Using Tabasco sauce, soda pop or similar products that never were intended for coins is something to avoid. At the same time, don't believe the lurid claims on the labels of the polishes on the market. Despite what they claim, they are not safe for coins and will do irreparable harm to them. "  

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Thank You and continued Good Luck in your collecting.