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