The objects

Stamps, notes and covers

On this page10

The honest answer first Why a jar is actively wrong here And the humidity target differs Which is why they should not share a jar Where this shelf does help The materials guidance applies to the enclosures And PET is the right plastic for the sleeve too Pressure and flatness are the actual requirement Which makes the jar an outer layer or nothing References

Paper is not a jar product, and this is the page that says why.

The honest answer first

Stamps go in polyester mounts and sleeves, in albums and stock books. Notes go in polyester sleeves. Covers go in sleeves sized for them. None of those is a jar and none of them should be.

Why a jar is actively wrong here

Paper stored loose in a container creases, curls and abrades against itself and the wall. Flat storage under light even pressure is the whole of the practice, and a jar is the opposite shape.

And the humidity target differs

Metal wants very dry. Paper does not want to be bone dry, because embrittlement is its own failure mode. Storing a stamp collection at the humidity a coin collection wants is not obviously doing it a favour.

Two materials with different humidity preferences, one of which is a sulphur source for the other. Sorting by material before sealing is not fussiness, it is the whole technique.

Where this shelf does help

As an outer container for enclosed material: a jar holding sleeved covers upright, dry and dust free, in a loft where the alternative is a cardboard box. That is a genuine improvement.

The materials guidance applies to the enclosures

Lignin free, acid free, buffered or neutral pH, and no kraft, office paper or glassine. That is about the sleeve, the album page and the mount, and it is where the money should go.

And PET is the right plastic for the sleeve too

Uncoated polyester is the first material named as suitable. The same material that makes 81 of the containers on this shelf is the one a stamp mount should be made of.

Pressure and flatness are the actual requirement

Album pages and stock books provide even support across the whole sheet. That is what prevents curl and crease, and it is the one thing no container shape can offer.

Which makes the jar an outer layer or nothing

For paper, use the right enclosure and then decide whether a sealed outer container helps with the storage environment. Skipping the first step and relying on the second is the mistake this page exists to prevent.

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

Library of Congress, Care, Handling and Storage of Photographs: "Suitable plastic enclosures are made of uncoated polyester, polyethylene, and polypropylene." On standards: "To be considered photo-safe, storage materials must pass the physical and chemical requirements outlined in ISO 18902 including passing the Photographic Activity Test (PAT)." And on humidity: "Photographic emulsions may stick to plastic enclosures if they are exposed to high RH, especially above 70% RH." loc.gov

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.