: Temperature and humidity really have little to do with it. The
: glass on the inside of the kayak (outside too for that matter)
: shrinks as it cures
: Bill H.

What you say about the epoxy shrinking as it cures is true, but that does not mean that humidity has no effect.

I have only ever seen the curing epoxy cause small changes, but I have seen enormous changes caused by humidity variations even after the epoxy had cured for several weeks. I had a small flat panel about a foot wide curve up almost an inch in the middle when we had a few days of rain, then it returned to completely flat by itself when the sunny weather returned.

Regardless of what causes the curling, spreader sticks can save a lot of struggling to get things to match later.