Why is superglue a liquid until you trap it between two surfaces?


Was gluing something back together the other day and I spilled some. The liquid on the worktop stayed liquid for a while but anything touching it was instantly stuck. Why does this happen?

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The oxygen in the air attaches to the glue and changes it, hardens it. When it is in-between paper you are using a tiny amount on a larger surface so the glue can oxidize faster than in the closed glue bottle and dries much quicker than the glue in the closed glue bottle. The glue in the bottle is drying too, just much much slower.

Superglue is substance called “cyanoacrylate”, which is in a liquid form but hardens into a solid if it reacts with even small amounts of water. There’s usually moisture on the surface of objects (or your finger), which is why it hardens if you stick it on something. There’s moisture even in air, which is why superglue will slowly harden over time if left by itself.