Fibre resin gone rubbery


New Member

I have bought a bulk of polyester resin and catalyst as my weekly shop to the local car repair shop was becoming too much. The catalyst is now a liquid instead of a paste, however it works fine and goes very hard like normal.

I was using it again today and instead of going completely hard it has gone rubbery. I am pretty sure I used the right measurements as they were the same as last time. What am I doing wrong? Too much catalyst or too little?

Here is what I am using if it helps:

Catalyst -
Resin -


Jr Member
From my understanding the runny catalyst shouldn't effect the mixtures hardening ability. Try making the next batch a little hot meaning put in more hardener than required it will give you less time to work with it but it shouldn't have a rubbery issue. Too depending on the temperature or moisture content outside it could be having a negative effect on the chemical reaction causing the rubbery condition. All in all though it's possible to just have a bad batch of chemicals which always leads to problems down the road.