Why doesn’t glue stick to the inside of the bottle?

Life’s little conundrums really get you thinking don’t they? Yesterday at work I sat and stared at a bottle of Elmer’s School Glue, trying to figure out how in the world that glue doesn’t stick to the inside of the bottle. I mean really you pour it out of the bottle onto something and it will stick that to pretty much whatever you stick it to, but it pours out of the bottle as a liquid and you don’t have to force it of the sides of the bottle.

Well finally I got up and went and got another bottle of glue from the back to see if it would be any different, and it was, the glue was stuck to the side of the bottle! And so that made me sit for another twenty minutes trying to figure out why in one bottle of glue doesn’t stick to the inside and in another it does. Finally, I stopped thinking and just looked; the bottle that had the glue stuck to the inside of the bottle was opened! And at last I had my answer, AIR!

When you squeeze the glue onto paper or whatever it is you happen to be gluing, it makes contact with air. So the water molecules start to evaporate and therefore the glue dries and sticks to whatever it is on. INSIDE of the bottle as long as it is closed air can not get to the glue, so the water molecules stay where they are and continue happily flowing amongst each other. However, once somebody leaves the bottle unscrewed or even open entirely the air gets to the glue and dries out all of the water molecules and that is when we end up with an almost brand new bottle of glue with a big giant opaque clump inside that just will not come out.

So from now on remember to turn the top on your glue bottles and let life’s little conundrum play itself out as long as it can. Because nobody is happy when you need a little bit of Elmer’s School Glue and when you go to squeeze it out you feel that big hard lump in the middle of your bottle, especially not those happy little water molecules that got evaporated. But if you do happen to forget to turn that top and you end up with a Elmer’s bottle with a rock of dried up glue inside, it can always be turned into a maraca with just a few not so gentle taps on the table to get the glue unstuck from the side of the bottle.

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