Hello,
I am aiming to make a cast out of the polyester casting resin, and I hope to submerge it afterwards and for it to remain water clear.

In my first attempt, when the cast was submerged, it formed an opaque white layer on the surface. I waited 24 hours before submerging my casting.
I was told that it clouded up because the polyester was not fully cured before I submerged it and that it would be water resistant if it was fully cured.

I was also told that it will take 30 days to fully cure at room temperature. I would like to speed up the curing process so I am looking into post curing.

So my question is what are suitable conditions for post curing the polyester cast? 
I read somewhere that 60C for two hours was good but that was for castings 1/8 inch thick.
The castings I have made are relatively large at 25cm by 10cm by 10cm.
Would gradually heating the casting up to 60C over a couple hours be better than just putting it in an already heated oven?

Thanks for you help in advance,
Hamish

The recommended post cure for the WaterClear Polyester Casting resin is to cure for a minimum of 24 hours a room temperature before increasing the temperature to 40C for 16 hours. A ramp rate is not necessary - larger blocks take a while to soak up the heat and the temperature change is not that high.

Many resins during the early cure stages are moisture sensitive and will have the  results you did with immersion/exposure to water.


Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant