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 — spread it or leave a bead?
Put equal amounts of white school glue on two matching smooth surfaces in the same room. Spread one into a broad thin film. Leave the other in a compact thick bead. Both are open to the same air. Which gets firm first?
Guess before time passes
Equal glue amounts, same air and temperature. Which shape loses enough water to firm up first?