1What white glue is really made of
Tangly sticky strings, floating in water
Glue isn't one smooth goo. Zoom way in and it's two things mixed together. Watch each one:
Tiny sticky strings
Glue is full of long tangly strings (grown-ups call them polymers). They love to grab onto each other and onto stuff — but only when they can touch.
Lots of water
About half of white glue is just water. The water gets between the strings and keeps them apart, so they slide instead of grabbing. That's why it pours.
2Two ways to leave a blob
The open smear vs the capped blob
It's the very same glue. The only thing that changes is whether the water has a way to sneak out:
The open smear
Spread thin and uncovered. The water can float up and away into the air.
The capped blob
Sealed under a lid. The water is trapped — it has nowhere to go.
3Your turn — take the water out
Slide the water away and watch the strings
Here's the zoomed-in glue. Drag the slider to pull the water out, then push it back. Watch what the strings do when their water is gone.
4Now race two blobs
Same glue, two blobs — one open, one capped 🕐
Two blobs of the exact same glue, both sitting out in the air. The left one is open. The right one is sealed under a cap, so only its water is trapped. This is the test: if air sets glue, both should harden; if it's the water leaving, only the open one will. Guess first — then start the clock.
Guess before you start the clock
Both blobs are out in the air. But the capped one is sealed, so its water can't get out. When glue sets hard, what's really doing it — air reaching the glue, or its water leaving? Pick the one you think wins, then watch.