Humidity Always Wins

Many of us assume that if a museum display case has a tray of silica gel, the case's humidity will remain permanently in a stable range.

This is not true.

99.99% of display cases are not sealed. They usually shouldn’t be. Air slowly exchanges with the gallery through tiny gaps (deliberate or not), cable penetrations, and maintenance access.

And every time you open the case.

If a case is very well-engineered, air exchange can be set to run slowly.

But unless the case is engineered like a spacecraft, the air inside will eventually equal the air outside. Every time.

What does silica gel do? Not what we might think.

It “buffers.” It acts like a shock absorber, not a force field. It slows humidity changes. And it only works if the case is nearly sealed. Otherwise, it doesn’t work at all.

And one day, the surrounding environment will win anyway.

A cooler on a hot day works the same way. It delays your beer from getting warm. But the outside air eventually wins.

When we confuse slowing change with stopping change, we risk damaging our collections. And wasting a lot of money.

Here’s the thing:

Silica gel in a nearly-sealed case is a temporary buffer. It never permanently stops humidity changes.

Humidity always wins.

Warmly,
Jonathan

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MtM Word of the Day:
Silica gel. A porous material used in display cases to absorb and/or release moisture in the air. It buffers short-term humidity change. In a well-sealed case, it slows air changes, but it can’t permanently isolate the case from the surrounding environment.