PVC Damage and Toning Can Cause Coins to Change Color
Toning
Toning is the result of chemical reactions. As coins are subjected to oxygen (and humidity), a chemical reaction occurs between the metal and environmental elements, like sulfur and oxygen. This reaction leaves a compound, or layer of tarnish, on the surface of the coin and slowly changes the color of its metal.
This is not an overnight but a slow process that takes years to develop. Toning most commonly occurs on silver coins but can also happen with other metals and alloys.
Does toning reduce the value of my coin?
Determining the impact of toning on a coin’s value can be straightforward: Does the toning make the coin more attractive? If so, it may increase the coin’s value.
PVC Damage
PVC damage comes from the reactions between metals and vinyl holders. Vinyl is commonly made with plasticizing chemicals to be more pliant since pure vinyl is brittle and cracks easily. These softening chemicals leach hydrogen chloride out of the holder onto the coin in a process called off-gassing.
The off gassing leaves a film on the coin that gives coins a greenish, milky, or cloudy appearance. PVC damage can also present as pitting, spots, splotches, and blobs on the surface of a coin. Copper coins are the most susceptible to PVC damage, followed by silver coins, gold coins, and platinum.
Coin holders like the Harco Coinmaster albums had high levels of PVC and were sold before the effects of PVC on metal were well known. While the Harco albums are no longer produced today, there are still older 2 x 2 flips to be wary of. If your dime has been in a plastic holder, it will be imperative to discern whether the green has come from PVC or toning.
How Can I Identify PVC in My Vinyl Holder?
All vinyl holders and coin flips will release a little hydrogen chloride over time. There is a method to determine if the vinyl has prominent levels of PVC, which is the Beilstein test.
Heat a bare copper wire under a gas flame. Touch the wire to the plastic while still hot to take a small sample. Re-insert the wire into the gas flame. Did you see a burst of green? If so, the plastic is PVC or similarly dangerous chemical.
Can I Repair PVC Damage?
While some PVC residue can be washed with a 30-second acetone wash (a process that requires following all safety precautions), the damage PVC causes to coins is irreversible. Once you have identified PVC damage and the affected coins, these should be kept apart from your other coins. PVC contamination will spread as the other coins supply feed material to the chemical process on the damaged coins.
Protect your coins and keep them in a safe storage container.
