Maybe there was a little moisture inside the board, working its way out?

If the separate bead kicked right away but the smear on the board didn't, maybe there was a significant enough temperature difference between the board and ambient that you need to let the board heat up a little bit first? (Or pre-heat it?)

Putting a blow-drier on it first could address the potential moisture and the temperature issues.

Like oipaul says, could also be an old batch. In the thicker bead, maybe you got a better distribution/mix of the resin and hardener.

Beyond the call of duty for this one, but in cloudy climates, maybe add a separate UV lamp?

Epoxy won't kick at all if the temperature is under 55 degrees, but your bead kicked, so that rules out too cold, and too old. It has to be an outside issue like water, as mentioned, or oils entrenched into the board itself, and perhaps a bad mix. If the stuff is still good, let the crack dry, rough it up to remove any oils and then apply.

I used to cheat some of these with Suncure poly. Sand it, remove the splintered glass, fill with Elmer's (a buffer between polystyrene foam and polyester resin), let glue dry, then coat with Suncure.



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I was right.

Edited: 01/03/2023 at 03:10 PM by Cole