Be very careful with the hot water. A while ago I was experimenting with soem twisted M3 Grant tracks. I had water that was certainly hot, but clearly not boiling, probably not even at a decent simmer. When I dipped the track into the water, it didn’t exactly melt but sort of shriveled. I did the other tread with the hottest water I could get out of my hot water heater about 130F, and the track straightened up nicely. I have subsequently used hot water from the tap with good results on other tracks that I actually intended to use.