Getting started

From hoard to storage

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One: sort by material Two: enclose individually where it matters Three: dry the air Four: seal it Five: label the outside Why enclosure comes before sealing And why drying comes before sealing too Check it, do not trust it References

Enclose before you seal. A sealed jar preserves whatever atmosphere and whatever contact you put in it.

One: sort by material

Copper, silver, paper and anything with a coating behave differently and off-gas differently. Mixing silver with paper in a sealed jar is putting a sulphur source next to a metal that tarnishes from it.

Two: enclose individually where it matters

Anything you care about goes in its own inert enclosure first. The jar is the outer layer, not the only layer, and this is the step that separates storage from a container of loose objects rubbing together.

Three: dry the air

Metal wants below 35 percent relative humidity. A desiccant pouch in a sealed jar gets you there and holds it, and the catalog carries fibre desiccant pouches for exactly this.

Four: seal it

A liner that actually seals, on a neck that actually closes. Without the seal the desiccant is simply exhausting itself against the room.

Five: label the outside

What is in it, when it was sealed, and when the desiccant was last changed. A sealed jar you have to open to identify is a jar whose seal you keep breaking.

Why enclosure comes before sealing

Because a sealed jar is a closed system. Anything acidic, sulphurous or simply abrasive that goes in stays in, concentrated, against the objects, for as long as the seal holds.

And why drying comes before sealing too

Sealing humid air into a jar preserves the humidity. The desiccant has to be in there at the moment the seal is made, and the jar should be closed in the driest conditions available rather than on a damp day.

Check it, do not trust it

A humidity indicator card in the jar costs almost nothing and turns an assumption into something you can read through the wall, which is one argument for a clear container.

References

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

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

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.