smoke/steam generated by fibreglass resin

[two stroke mick]

I was trying to make a mould to make a base for a bench seat. I was making a mould from a plastic bock but it had 4 deep pockets circa 10mm in depth. I poured resin into these pockects and left the unit for about 30 minutes. when i came back there was smoke/steam comming of the resin I dumped the resin out of the mould before it could go off. the mixture was at about 3 percent mek to the resin.

I think i put in too deep a layer of resin and it boiled up. any thoughts/ suggestions

tsm

[Poly]

Resin curing is an exothermic reaction (it gives out heat). The reaction goes faster the hotter it gets, so you can get into a spiral where the heat generated makes the reaction quicker which makes even more heat which makes it even faster and so on. Its known as a run away reaction or "thermal runaway". It can potentially be quite dangerous with the risk of catching fire. The fibreglass gurus on here will be able to tell you how the usually manage it - but in general the principles will be increasing the surface area : volume ratio - so the heat is better able to escape, keeping quantities of material low so the total amount of heat generated is less and possibly reducing the amount of hardner so the reaction is slower to start with.

[boilermaker1]

sound like too much hardener

[Dirk Diggler]

too much catalyst, 1% is sufficient this time of year, and pouring resin into a mould is a no no. Wet out some chopped on a bit of cardboard, hardboard or similar, and drop it into the mould, poking it into the corners with a brush!

[gibberfish]

It's a good warning to folks.
Years ago on a big job we left 3 inches of unused gel coat in a bucket. It caught light and burned very fiercely.

If you ever find yourself in a situation where you need to abandon a bucket of mixed resin be sure to put it outside away from flammable things. Better still, top the bucket up with water.