In order for your glue to perform properly, it must be able to penetrate (or "wet") your substrates. Some substrates are more difficult to penetrate than others. This is a result of varying surface energies.
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Dyne Levels play a major role in proper adhesion, and here is why:
The Dyne Level of a material is called its surface energy. When glue is applied to a substrate, its “wettability” is impacted greatly by its surface energy and that of the substrate.