I used Art N Glow resin. I measured equal parts of hardener and resin, mixed for three minutes in a room temperature setting, and my resin cures strangely. At first when I take them out of the mold(72 hrs later) they are hard, over time if it gets a little warmer (75 F)they get bendy, and if i dip them in cold water they harden fully again. Why does this happen and could someone help me fix this problem?