Filler powders can certainly help thermal stability and reduce shrinkage so yes it might help.  Just be careful how much you use as most, in significant quantity, will turn the casting white, so you may need to take this into account.

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant

Thanks, I'll do some tests with less MEKP and see how it goes.

Also, do you think adding a filler such as talc would help reduce shrinkage/heat generation?

The mould would have had a centre insert to keep the casting with a sensible wall thickness.  If the wall thickness isn't too thick then not too much heat will be generated.  Lowering the MEKP ratio will also help a lot. The slower and lower the temperature of the cure, the less likely shrinkage is a major issue.  You can also, to an extent, calculate the effect of shrinkage with some polyester resins.

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant

Hi All,

I've just joined the forum as this place seems to contain a wealth of knowledge and I'm looking for some help!

I'm trying to cast some large resin plinths. They'll be up to 50cm cubed and will be hollow but with walls about 20-30mm thick.

I'm basically trying to recreate this effect in the image below which are polyester resin. However, from researching polyester resin it seems that I'm going to have problems with shrinkage/warpage and dealing with overheating. Some people have advised me to use epoxy but obviously it's a lot more expensive.

Can anyone shed any light on how the below have been made with polyester resin?

Thanks