What is "air-dried"

Usage examples of "air-dried".

Swim bladders from previous catches of sturgeon, carefully washed and air-dried to hard, clear, isinglass balloons, served as floats for the net, and stones tied to the bottom were weights.

The pale beer would be made from the air-dried white malt, while the dark gained it's color and smoky flavor from malt dried over a wood fire.

As this was the case, malt would also sometimes be air-dried and then lightly smoked, when labor was cheap but fuel expensive.