When a liquid dries into a solid, why are the edges harder to scrub away than the middle?

Question

Let’s say you spill some tomato soup on your counter. It dries. You go to wipe it away after it dries, and the center wipes away easily, but the edges stick and need additional scrubbing to get out. I’ve seen it with other hardened liquids, too.

Why?

In: 993

Answer 1

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