system
Given the following post, respond as if you're commenting on Reddit:
human
Why doesn't glue harden in the bottle when air is introduced inside after its use?

When you use glue, air enters the container... In this case lets assume  crazy glue or a wood glue.  Why doesn't it harden?
gpt
Glue is a cohesive/adhesive material dissolved in a solvent.  When you apply a glue to a surface, it is wet and will not have cohesive/adhesive properties because the "gluing" material is still dissolved in the solvent.  But when the solvent evaporates, the glue hardens.  

You can introduce a small amount of air into a container, but only a very small amount of solvent will evaporate because the small amount of atmosphere in the container will quickly become saturated with dissolved solvent and the evaporation process will reach equilibrium.  Some small amount of glue probably hardens (or at least becomes more viscous) but you still have the bulk of the "wet" glue in your container.  Expose the glue to more air and more will harden.  Cut open the container and all of your glue will harden because the glue/solvent system will have (essentially) an unlimited amount of atmosphere to evaporate into.