Posted on 4/12/2016
Residue caused by PVC holders can often be safely removed by NCS conservation. If left untreated, this residue can permanently damage a coin’s surfaces.
The phrase “PVC residue” can strike fear into the heart of any numismatist. While such residue is a major concern, not all hope is lost when a coin has been contaminated. Understanding how the residue forms is a great help in calming the initial fears. Luckily, there is a course of action to take in alleviating this too common problem.
Flips are among the most common type of coin holder used in the numismatic community. So common that they are the required way to submit raw coins to NGC for certification. In their most common form, flips are a clear plastic double pocket holder that folds over into a convenient to use square. One pocket is generally used to house the coin and the opposing pocket for a paper with pertinent information about the coin. Flips come in two distinct varieties based on the type of plastic used. One version called soft contains a plasticizer commonly known as PVC while the hard version does not contain this chemical. The concern is the soft flips that contain PVC.
While initially neutral, PVC has an unfortunate habit of leaching out of the plastic holder and forming a dangerous residue on the surface of the coin inside. The process of becoming a residue is accelerated by humidity, temperature, and the ambient air. Early PVC residue development is a light white or pale green haze. Advanced development of PVC residue will cause green spots to shiny green globs on the surface or high points of the design, those points in direct contact with the holder, to turn jade green. Severe PVC residue development will cause a shiny green layer to completely cover the surface of the coin. This residue is not only unattractive but will begin to corrode the surface of the coin and is permanent. The corrosion caused by PVC residue is a continual process which is why NGC will not certify a coin with active PVC residue.
Once it is determined that a coin has PVC residue the natural question is what can be done to rectify the situation. NCS conservation can effectively remove PVC residue from the surface of all types of coins. If the PVC residue has not damaged the surface of the coin underneath, the coin can be certified by NGC. In some cases the PVC damage is so severe that coins are NGC Details graded with environmental damage but can still be certified as the active residue has been removed. A coin with PVC residue can have additional problems that may cause it to be Details graded such as Improper Cleaning or other damage. These sorts of additional problems are independent of the PVC residue.
With all this potential harm, it is a surprise that soft flips are still used in the marketplace. Many coin dealers find flips an ideal holder when dealing with large quantities of coins in inventory. The more flexible and less brittle nature of a soft flip has advantages when moving quantities of coins from place to place. Even in these cases the soft flip is purely a short-term storage option. Once the coin has left a trusted dealer’s inventory and become a part of your collection it is time to abandon the soft flip in favor of a better holder for long-term storage. Using hard flips is also the best way to submit your coins for certification to NGC. Even in the relatively short time coins are in flips before certification by NGC, PVC can begin to affect the surface of a coin.
If you are unsure what type of flip you may be using, a few simple tests can be performed. PVC flips will smell of vinyl while non-PVC flips will generally not have any noticeable odor. Gently fold the flip in a spot not designed to be folded. A holder that sharply folds, or even breaks, is likely a non PVC hard flip. A holder that slowly unfurls back to it's original shape is a soft flip containing PVC.
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