Desiccant or Silica Gel?

Climate conditioning for display cases is confusing.

One confusing part is what we call the stuff we condition with. Despite what we hear, it’s almost never “desiccant.”

A desiccant is a drying agent used to remove moisture from air.

But silica gel is a porous material that can absorb and release moisture.

Many of us call the material inside a display case desiccant (I know I have). But that is not the right word. More importantly, it’s not the right stuff.

A desiccant dries things out. A display case usually should not do that. Most artifacts do not want the driest possible air. They want stable air, within an appropriate range.

Museums do use desiccants. Not in display cases, but in shipping crates, temporary storage, and for mold prevention, where the goal is only dryness.

Inside most display cases, the goal is not just drying, but buffering. Silica gel is almost always the correct material for that job. It slows humidity swings in either direction by absorbing or releasing moisture as conditions change, provided the case is engineered to be nearly sealed. (More on that next time.)

Here’s the thing:

If the goal is display case stability, say silica gel.

If the goal is just dryness and it's not for a display case, then sure, say desiccant. (Just don’t try to spell it.)

Warmly,
Jonathan

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MtM Word of the Day:

Desiccant. [DESS-uh-kint] A moisture-absorbing material used in museums when the goal is to dry or protect enclosed spaces from excess humidity. It may be used for packing, emergency drying, or mold prevention, but it is not the right substance for buffering in display cases.