Polyvinyl chloride damage is caused by storing coins in soft plastic flips that contain polyvinyl chloride (PVC.) PVC generally manifests as a light-to-dark greenish residue, although it can appear as milky or light grey in color. It has a distinctive "plastic" odor which can range from subtle to strong. I recommend treating coins for PVC residue whenever you can smell PVC on them, even if you do not see the greenish residue yet, because if the coin has a plastic smell, the PVC decomposition process has begun.
Time involved: around 10 minutes, including preparation and clean-up time.
1. Put on latex gloves and eye protective cover. Be sure you have good ventilation, and avoid utilizing the kitchen or any area wherever an open flame is present. Acetone is a potent chemical that is highly flammable. Although acetone does not burn the skin (it is a cardinal component in many nail polish removers,) you should avoid unnecessary contact.
2. Pour out a very small amount of acetone into the container. (Do not use plastic as acetone will melt it.) You only need about 1/4 to 1/2 ounce if you use a small drinking glass, or tiny jar. You need only enough to cover the coin by about 1/4 inch.
3. Gently put the coin with PVC residue into the dish, and swirl the acetone around for about 30 seconds. If both sides of the coin are affected, turn it over and swirl the other side.
4. Remove the coin and allow it to air dry. If the PVC residue is still present, continue with Step 5. If the coin is clean, go on to your next coin, and when finished dispose of the acetone by pouring it into a resealable jar. Never pour acetone down a drain, or let more than a very small amount evaporate. Acetone is considered hazardous and must be handled appropriately.
5. If the coin still needs additional cleaning after swirling (and in my experience, most do), take a cotton swab (such as a Q-Tip) and dip it into the acetone. (Do not use cotton swabs with plastic sticks!) Then, using a firm and steady hand, roll the swab across the coin's surface on the PVC-infected areas, taking care not to employ any kind of rubbing or abrasive maneuver. If the coin has a lot of PVC residue, you should replace the swab every few "rolls." Keep rolling, using new swabs as required, until the coin looks clean, and then swirl it again to finish.
1. Never rub the coin with the cotton swab. Apply only rolling movements. The slightest abrasion may cause hairlines to the coin's surface.
2. Occasionally PVC residue can be stubborn and won't respond to rolling. Try soaking the coin in a sealed jar of acetone for 24 hours before undertaking the rolling maneuver again. If rolling still fails, attempt additional intensive, higher-pressure "swabbing" (but don't "scrub!") If the PVC residue still does not respond (in other words, if the swab Is not picking up anything at all,) your coin might not be cleanable (or perhaps it's not PVC residue that you see on the coin.) You could try sending it to NCS for expert preservation.
3. To prevent future PVC damage, don't store your coins in soft or flexible plastic flips. Use the more rigid Mylar flips instead. Never store your coins in any sort of plastic containers that have a smell.
What You Need:
* Full-strength acetone (sold where paint supplies are found)
* Small glass or metal dish (PVC melts plastic!)
* Coin with PVC damage
* Latex or rubber gloves
* Protective eye-wear
* Cotton swabs (such as Q-Tips)