Why does My Material not Gel in the Time Specified on your Datasheet?

Gel times are dependent on mass, temperature, and the geometry of the material during cure. The gel time listed on a datasheet is a result of a test run at a specific temperature (usually 25C), a specific mass (i.e. 100 grams), in a specific geometry (a plastic beaker). Whenever one of these three change, it can affect the gel time. Warmer temperatures will speed up the gel, lower temperatures will slow it down. The more mass you have, the faster the material will gel. Material geometry matters because material in a large mass will gel more quickly than material spread out (i.e. in a cup vs. spread on a tabletop).