How do they keep the glue in the bottle from sticking to the inside?

Factual Questions
1

I’ve always wondered how the kept it from sticking to the bottle.

2

There’s three kinds of glue. Well two really, but we’ll say athree for convenience. There’s moisture-cured, two-part, and evaporative. Moisture-cure glue is a type of two-part, that requires atmospheric moisture to cure and set. There isn’t enough moisture inside the bottle to start the curing process, so the glue stays fluid. Two-part glues have two components that must be mixed in order to set. Evaporative glues are dissolved ina solvent which must evaporate to set the glue, but it can’t so so in the container, when it’s sealed. If the containers that the glue is in is left open, however, both mosture-cured and evaporative types will set.

3

In other words…

Elmer’s Glue needs to air-dry, Aslan, and as long as you keep the top on the bottle, not enough air can get in there to dry out the glue. But if you unscrew the whole top and remove it, thus letting lots of air in there, it’ll all dry out. And over time, if you don’t keep the orange thingie tightened down so the tip is totally closed–if you put away the kindergarten glue bottles for the summer with the orange thingies not tightened down–enough air will get into the bottles to make the glue dry out somewhat and then it’ll be too gloppy and sticky to come out the tip.

Same thing for rubber cement–it needs air to dry, and as long as you keep it tightly capped, to keep the air out, it’ll stay wet. But the solvent that rubber cement is dissolved in is much more volatile than the water that Elmer’s Glue is dissolved in–it evaporates into the air much faster than water. So every time you take the top off the rubber cement, it loses some of its solvent to the atmosphere while you’re working on your project. So rubber cement gets thicker in the jar faster than Elmer’s Glue does, and you have to add thinner to it.

4

So is that clear? There’s no air where the Elmer’s Glue or rubber cement is touching the side of the bottle, so it can’t stick.

5

There’s also the fact that glue bottles are typically made of polymers that are ‘waxy’ - polyethylene and the like - these plastics are rather hard to stick with glue anyway.