I’m back everyone!!! I know, doesn’t look like the right picture but its still glue!!!
You may have heard this question before but I’ve always wanted to know the answer. So I’d thought I share it with you guys…
Most glue doesn’t stick to the inside of the bottle because it needs air in order to set. If you leave the cap off of the bottle or as the bottle gets closer to empty so that more air is inside the bottle, the glue will get stickier. Some types of glue require a chemical other than those found in air. These types of glue won’t stick to the bottle even if you leave the cap off.
See, glue is made up of a substance that sticks to things and a solvent that keeps it liquid until you want it to stick. When you put glue on a piece of paper, the solvent gradually evaporates until the glue becomes sticky. When the glue is in a bottle, there is a space inside the bottle above the liquid that is full of air. So why doesn’t the glue dry out? Well there’s a limit to the amount of solvent that can evaporate to fill the space in the bottle. Once the space is full of solvent gas, no more solvent evaporates from the glue and the glue stays runny.