I’ve been making one off resin vases, casting around 1 litre of epoxy, in pvc molds. This may sound a strange choice of material for a mold but my designs require blending of colours at the edges rather than uncontrolled merging. To obtain the required effect, I zap the resin in a microwave and through practiced timing, pour just before the jelly stage. The approach generates huge exotherm, however I can control it via a water bath in the centre of the pvc mold and wet cloth on the external part of the mold. The success rate is high and the resultant effects can be really attractive. So much so that I have several commissions.

The problem is that the pvc molds take a great deal of work to make and are one offs. To try and introduce some efficiency I have made molds out of silicone though without success. Silicone’s insulating properties mean it is impossible to control the exotherm.

Ideally, I would like to use a low exotherm translucent resin but have been unable to find anything in Australia at a reasonable price.

Any suggestions on either molds or casting material/techniques very much appreciated.
Cheers

Look for Smooth-On Crystal Clear 206.

This is a water clear urethane casting resin that has been used for casting sculptures up to 10 tons in a single pour.

The issue though, is that any mass casting resins that are designed to avoid exotherm are going to cure very slowly. The 206 has a pot-life of 4 hours and a demould time of 5-7 days (and I would leave it longer unless you can post-cure as urethanes have a tendency to 'sag'). I'm not certain this would work with the technique you are using.

I also wouldn't recommend putting this stuff in the microwave... Even epoxy is extremely unhealthy, but urethanes can be one of the most toxic substances on the planet. If you need to heat it up, build a dedicated curing oven that doesn't come into contact with food... You could build a small simple one for less than $50 with a bit of thought. 

Thanks Hanaldo, I’ve actually been looking for ages for something like the 206 for another project so I’m very happy at finding out about it - though the toxicity side of things is a bit scary.

Its also an expensive option for this project at over $135 a liter. I can get clear epoxy for $15 a liter which enables a profit margin.

Thanks also for the epoxy hazzard warning, I have perhaps been a little lax.

Cheers
Phil