This morning, knowing that it was going to be a sunny day without rain, I took the dubious UV resin pieces that I hadn't already thrown out (a rose, a starfish, and three teardrops) and put them on the back step so that they would be out in the sun ALL DAY. When I got home, I retrieved them, and they had set solid, no squishes or sticky bits. Yay! So I think that supports my theory that there wasn't enough UV in the sunlight when the sun had reached too close to the horizon. I mean, that's why we have sunsets anyway, why they're red and orange and pink.