PVC damage on coins is the result of improperly storing coins in soft plastic flips or other plastic coin holders that contain PVC. The PVC chemical in the flips interacts with the metal of the coin creating a slightly acidic reaction, which causes residual deposits to appear on the coin's surface. Copper coins are most vulnerable to PVC damage, followed by silver, and then gold and platinum.
PVC damage appears as greenish, milky, or grey streaks or haze. In severe cases, it looks like tiny green blobs on the surface of the coin. PVC stands for polyvinyl chloride; it is an additive used in plastics to make the material more pliable and less brittle. In coin collecting, PVC is most frequently encountered in the clear plastic flips in which coins are stored.
As a general rule, the softer and more pliable the flip is, the more PVC it contains. The hard, stiff, brittle types of flips (made of Mylar) do not contain any PVC. Also, some plastic or Ziploc® bags may be safe for storing your coins. The best long-term storage option is an archival quality plastic bag made of pure polyethylene or polyester.
If the PVC residue on the surface of the coin is removed soon enough, the coin may escape with minimal damage that is not visible to the naked eye. If the green PVC residue is left on the coin for a long time, it will start eating into the surface of the coin. When the green PVC residue is removed, it will reveal the extent of the damage. In extreme cases, this will leave a series of microscopic pits and indentations that cannot be repaired. Copper coins and coins that contain copper in their alloy are the most susceptible to PVC damage. Conversely, gold coins are the most resistant to being damaged by PVC residue.
How to Determine If the PVC Contains Plastic
PVC residue has a distinctive smell, sort of like the smell you get when you open a cheap plastic toy. In mild cases of PVC contamination, you might not be able to detect the smell, but if you ever smell PVC after removing a coin from a soft plastic flip, even though you don't see contamination on the coin, you should treat the coin for PVC damage anyway as a precaution.
The only positive way to determine if there is PVC in the plastic that you are using to hold your coins is to have it analyzed by a chemist. Unfortunately, most coin collectors do not have access to such a person nor would they be able to afford the analysis at a reasonable cost.
Another way to determine if a coin holder is made from plastic that contains PVC is to do a "destructive" test on the coin holder. This means that you will have to destroy your coin holder or album page to test it. Given that most coins cost more than the holders they are in, this may be a good investment of your money.
To do this test follow these simple steps (Note: This test should only be performed by a responsible adult):
- Take a stick pin (like the ones that is used in sewing) and poke it into the eraser head on the end of the pencil.
- Slightly heat the head of the pin with a lighter. Make sure it is hot enough to melt the plastic but not glowing red hot.
- Use the hot pin to melt some of the coin holder's plastic onto the head of the pin.
- Use the lighter again to heat the melted plastic on the pinhead until it starts to burn.
- If the flame from the small amount of burning plastic has a green hue to it, the plastic more likely than not contains some amount of PVC.
How to Remove PVC From Coins
Removing PVC residue is simple but left untreated, it will eventually eat into the surface of the coin. Merely taking the coin out of the offending flip isn't enough; once the PVC cycle has begun, the acidic PVC cycle will continue to degrade the coin's surface until permanent PVC damage results (see the photo above). Reputable grading services will encapsulate coins with PVC residue on them, however, they will indicate on the label that the coin has surface damage. This can significantly reduce the value of the coin.
Edited by: James Bucki