How come liquid glue doesn’t dry up inside the bottle when it’s exposed to air?

Question

Especially after using the same bottle of glue repeatedly

In: 22

Answer 1

Many types of liquid glue generally don’t dry up because the glue is exposed to air.

There is a solvent inside glue (typically water or ethyl acetate), and once this evaporates the glue becomes hard. It can only do so when there is a lot of air for the solvent to evaporate into, much more than what ends up inside the bottle.

P.S: Note that this applies to the glue regular people come into contact with. Industrial glues function in many different ways, and for example many industrial glues do chemically harden (for example if they come into contact with water which sets off a curing process).