The bottom of the unit relies on a 10mm thick Polyester resin mold to hold everything together…..I cannot get production or ANY consistency with this. Whatever I try.
I phoned a Representative of a local company that specializes in stuff like this and he said I should mix talc or any similar powder which would thicken the resin and hence stop shrinkage. I did it to the Max. I ended up with shrunken molds still…that now smell of baby powder when dry.
I am at my wits end.
I have done a lot in glass and can offer a few tips, but its hard to know exactly what you are trying to do from information given.
For starters if you are casting a 10mm resin block yes you will get shrinkage due to the temperature generated by the curing process of the resin.
Resin has no strength without glass added, you would be best to do a lay up with resin and several layers of glass first, allow this to cure (24 hours) as its thin the temperature wont be to high and the shrinkage will be next to nothing.
Then build the mold up in further layers of glass and resin staying under 1/4 inch thickness in layers, again to keep the temperature down with curing, dont leave it more than a couple of days between layers or the bonding will not be as good.
Another method would be to cut a section of several layers of plywood and use that as a spacer within the resin casting, as the plywood will displace a lot of resin and this will decrease the overall volume of resin so it will lower the temperature generated by the curing process.
The other important thing to remember is the % of catalyst used, the greater the % of catalyst the higher the shrinkage will be, You should always weigh your resin out, and add 2ml of catalyst for every 100 grams of resin, (2% by weight) if the weather is hot then i reduce the catalyst to 1 ml per 100 grams, for thick resin casting i would only use 1% catalyst.
Another factor is old resin will set faster and generate more heat than fresh resin, so if the resin you buy has been on the shelf in store for some time it will be crappy to work with compared to fresh resin.
There is also "casting" resin avaliable which will not cure so fast and generate so much heat.
Using talc is common, but baby powder is normally not talc nowdays, so not the best to use.
If you post some photos of what you are doing and the failures you have had i might be able to help some more.
Pete.