The plastics

PVC, and why it is named

On this page9

The statement Why PVC is the problem Collectors know the symptom And it degrades to something acidic It keeps appearing because it is cheap and clear This catalog holds very little of it But do not shrink-band a collection jar How to tell References

NARA names it directly: "Do not use... plastics containing PVC".

The statement

"Do not use office quality paper, kraft paper, plastics containing PVC, or glassine enclosures." Four named materials to avoid, and PVC is the plastic among them.

Why PVC is the problem

It is plasticised to stay flexible, and the plasticiser migrates out over time. What it migrates onto is whatever the plastic is touching, which in this craft is a coin or a stamp.

Collectors know the symptom

The green film on a coin that has sat in a soft flexible holder for years. It is the plasticiser and the degradation products of the PVC itself, and removing it is a conservation job rather than a wipe.

And it degrades to something acidic

Deteriorating plastics emit acidic vapours, which is why a metal coupon is used to detect an off-gassing plastic: the metal corrodes. In a sealed jar there is nowhere for those vapours to go.

It keeps appearing because it is cheap and clear

Soft, flexible, transparent, inexpensive. Everything a collector wants from a holder, which is exactly why the bad holders are so common.

This catalog holds very little of it

52 PVC items across 2,150 products, and 50 of them are shrink bands, sleeves and bags. The other two are an f-style bottle and a cylinder. Nothing on this shelf is PVC.

But do not shrink-band a collection jar

The one PVC product a collector might plausibly reach for here is a shrink band for tamper evidence, and putting a PVC film around the mouth of a jar that is meant to hold metal for decades is the one thing on this page to avoid.

How to tell

Ask the supplier for the material. For a holder already in a collection, the soft, floppy, slightly oily ones are the suspects and the rigid ones usually are not. If in doubt, move the object.

References

National Archives and Records Administration, holdings maintenance for photographs: "Do not use office quality paper, kraft paper, plastics containing PVC, or glassine enclosures." Materials should be "lignin free, acid free, and either buffered with an alkaline reserve or of neutral pH". archives.gov

National Park Service, Conserve O Gram, on the storage of metal objects: metals corrode in the presence of moisture and pollutants and should be housed below 35 percent relative humidity, stabilised in a dry microclimate using a desiccant such as silica gel. Deteriorating plastics emit acidic vapours that corrode metal, which is why a metal coupon is used to detect an off-gassing plastic. nps.gov

The Davis Pack Supply catalog, measured 18 October 2026. The numismatic and philatelic shelf is 391 rows: 146 containers and 245 closures. 81 PET, 64 PP and 1 glass, from 6 to 250 mL with a median of 118. Zero PVC. By colour 39 white, 35 clear, 23 black, 15 amber, 15 natural and 8 blue. Necks 70-400 at 113, 89-400 at 93 and 58-400 at 66.

Written from Library of Congress and NARA preservation guidance and from National Park Service Conserve O Gram material, and from the catalog as it stood on 18 October 2026. Conservation advice for a specific object is a job for a conservator; nothing here is a substitute for one, and a valuable or unusual item deserves that conversation rather than a jar.