What is PVC residue?
PVC residue is a surface contaminant that may be caused by storing a coin in a soft, pliable vinyl flip. The amount of time a coin needs to reside in a vinyl flip before the PVC film develops will vary significantly, depending on temperature, humidity, the age of the flip, and the type of coin. Under optimal conditions, PVC residue can begin to form in as little as two weeks. At ANACS, we only use Mylar flips. Mylar flips are free of all PVC.
The composition of a coin is a strong factor with the formation of PVC residue.
A gold or platinum coin will be the most resistant, a silver coin is next, and a copper or copper-nickel coin will be the most susceptible. Copper and copper-nickel coins are also highly susceptible to corrosion and/or spotting from excessive moisture and high emperatures. Due to this, collectors need to be extra careful with their choices of storage materials for these coins.
During the manufacturing process for soft vinyl flips, an agent is added to increase pliability. The main reason for this is to allow the flips to be reused without breaking or tearing. This softening agent will migrate out of the plastic over time, and becomes the surface film that is called “PVC Residue.” As this film continues to degrade, it eventually turns into a mild acid, and begins to attack the surface of the coin. Until the film is removed from the coin, it is usually not possible to tell if the coin has been damaged. Additionally, this chemical reaction can continue even if the coin is sealed in an inert plastic holder. This is why ANACS does not encapsulate coins with active PVC contamination.
Recognizing PVC residue is not always easy. When the residue begins to form, it often appears as light milky spots on the coin. PVC residue also appears as streaks or a light haze, and ranges from nearly white to dark green or gray. If the coin has enough ontamination, and your sense of smell is good, you will detect an odor that imitates the smell of a new plastic shower curtain.
For most coins, removal of PVC residue is a simple process. Gold, platinum and silver coins are easier to decontaminate than copper and copper-nickel coins, and business strikes are easier than Proof coins, but as with any coin, proper caution must be utilized. Pure acetone is the best solvent for PVC residue removal, and like many solvents, acetone must be handled properly in a controlled environment.
When using acetone, proper ventilation is a necessity, and extended exposure is not recommended. Wearing chemical-resistant gloves and eye protection is a good precaution against accidental acetone contact with your skin or eyes. You also need to avoid any type of open flame or spark, as acetone is highly flammable. If you are uncomfortable with these types of procedures, it is recommended that you make use of a PVC removal service to decontaminate your coins.
Pour a small amount of pure acetone (the kind you can purchase in the paint section of a hardware or home improvement store) into a small glass or metal container. Acetone can eat through plastic, so using a plastic container is not recommended. With light PVC residue, gently swishing the coin back and forth in the acetone while holding the coin with a gloved hand will often remove the residue. Let the coin air dry afterwards on a soft cloth to avoid damaging the coin’s surfaces, and then inspect carefully.
With heavier residue, or contamination that has been on the coin for more than a month or two, more effort will be required. In these instances, the use of Q-tips can handle the residue. Begin by soaking the head of a Q-tip in the acetone, then carefully roll the head of the Q-tip across the surface of the coin. Make sure that the head of the Q-tip stays wet, as a dry Q-tip could scratch the coin. Continue to work the surfaces of the coin for about 15 seconds or so, then inspect the head of the Q-tip. If the process is working, you should see a green, gray or brown discoloration on the cotton tip.
Throw the first Q-tip away, and repeat the process with a second Q-tip. Continue until the head of the Q-tip remains white after working the surface of the coin. Once this happens, turn the coin over and perform the same operation on the other side. After all visible PVC residue has been removed, and the Q-tip stays clean, place the coin on a clean, soft cloth and let it air dry. You can also give the coin a few light swishes through the acetone, to remove any remaining traces.
As with any restoration process, proper care must be used at all times to prevent damage to the coin’s surfaces. Experiment with low-value coins first to familiarize yourself with the process. Done correctly, using pure acetone to remove PVC residue will not harm the surfaces of a coin, but if performed improperly, you could end up with a hairlined or otherwise damaged example.