Recognizing Coin Holders That Contain PVC
Posted by David W. Lange, NGC Research Director on 12/23/2009
You’re at a coin show or a dealer’s shop when you ask to see a coin that’s in a flip, one of those double-pocket, plastic envelopes that so many dealers use to display uncertified coins. When he or she hands you the flip, it seems that the coin is actually stuck to the inside of it. Some flexing of the soft flip is enough to make the coin break free, and then you see it—that pale green outline of the coin imprinted on the inside of the flip. You, my friend, have experienced a PVC moment.
PVC is short for polyvinyl chloride, a popular and widely used plastic that has countless industrial applications. In most of these applications PVC’s qualities are completely benign. In fact, using this plastic for coin flips is OK, too. Where the problem lies is that such storage is suitable only for the short term, say, less than six months. After that time the chemical softening agent that gives PVC its great flexibility may start to leach out. Over time, this can settle onto a coin and deposit an oily film—that sickly, green slime that leaves an outline of the coin on the flip and adheres to the high points of the coin itself.
Prolonged exposure to PVC deposits in the presence of moisture can actually lead to the formation of hydrochloric acid which permanently scars the coin. In its earlier stages, however, PVC film is removable with proper conservation. Any coin displaying such green, oily film on its surfaces may be submitted to Numismatic Conservation Services, LLC (NCS) for removal of the contaminant.
Using PVC coin holders is perfectly all right for short term storage and display. If a coin hasn’t sold after a few months, the dealer should place it in a fresh flip, but this doesn’t always happen. Collectors should never use PVC products for long term storage, a fact which became abundantly clear when a particular brand of coin album had to replace this plastic in its product line with another, less harmful one about 20 years ago. The damage to the products’ reputation, however, was irreversible, and the company went out of business. Old-time collections still come onto the market in such albums, and they’re not a pretty sight.
So how does one know whether a particular plastic holder is PVC or not? Well, one old test is to hold a copper wire to the flip and expose both to a flame. This will produce a blue-green color which reveals the presence of chloride. NGC and NCS do not recommend burning plastic in this ill-advised game of Mr. Wizard, and there’s a much easier test to determine whether a particular plastic is PVC. Simply twist the flip, for a start. If it bends quite easily and shows no indication of fracturing or creasing, it is almost certainly PVC. This quality is what makes it so useful in the short term storage of coins for sale.
Other types of plastic can mimic this quality to some degree, but only the PVC flips are nearly indestructible in normal handling. Acetate or polystyrene flips offer greater chemical protection, but they have limited flexibility and are intended for one-time service; repeated use will cause them to split, deciding the issue of long term storage right then and there. The most chemically inert plastic flips are also the most rigid—Mylar® is a trade name for a very safe plastic that is used for storing both coins and notes, but it must be handled gently. Mylar® flips can split at their joints and are not recommended for shipping purposes. If you submit coins to NGC or NCS at a show, you may notice that both companies use acetate flips as the best compromise between chemical and mechanical protection.
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