John in NM
We used to have that problem with West system if it was a huge void being filled, it would start to smoke and boil a bit. Often we got around that by using some filler wood to simulate a knot or something similar - I never got the hang of that look, but some of the guys were very good at it.

Lately I've been making a lot of parts out of urethane resin, and that stuff gets hot - it also picks up moisture readily, so I've had a couple pours do the boiling routine. You end up with about 10x the volume due to the moisture boiling, and end up with a huge mess where ever you were working (hopefully not the kitchen counter ). Another time I tried a new colorant, that was glycol based and worked well with regular epoxy, but not with the urethane - same result, a big foamy mess.