I'm thinking of that type of glue that you apply to both sides, let dry and then press together. Like this. It seems counter intuitive.

Other glues behave in the opposite manner, and get less sticky as they dry. So does duct tape. So does jam. And actually everything else I can think of. The container recommends letting the two parts dry to touch dry. It grabs really well even if you leave it quite a bit longer.

So what goes on inside contact glue?

  • $\begingroup$ What I can say is to take drying and gluing (curing) distinct. First the solvent - that is in the formulation because we must be able to apply the glue - must be let evaporate. Then polymerization and crystallisation take place. The example of jam or glue as in post-it is different as for there is not a real chemical bonding within the glue. Adhesion relies on weak interaction only. $\endgroup$
    – Alchimista
    Apr 3, 2021 at 11:51
  • 1
    $\begingroup$ @Alchimista It's my sloppy language, sorry. I do understand the difference between curing and drying. Cement and Gorilla glue both cure rather than dry, yet neither becomes stickier as they do so... $\endgroup$
    – Paul Uszak
    Apr 3, 2021 at 12:39
  • $\begingroup$ Still, it seems the point. When the solvent is there, no bonding and crystallisation take place. Some glues works on weak intermolecular force and cannot glue once dry. They need solvent to arrange between them and the parts to be connected. Other glues work on polymerization and the reaction can be effective from the first seconds but also take up to ours. One type does glue because of drying, the second one needs to dry to start curing. $\endgroup$
    – Alchimista
    Apr 4, 2021 at 11:07


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