Based on the idea that you are using correct process parameters on your TDS from mat'l supplier, you don't mention how you are degassing the material or how you are dispensing it into the molds. How are you meter, mix, & dispensing? Hand mixing? Eliminating the air in the material may help...
I suggest for a cheap prototype go to www.devcon.com
and request a cataloge or call one of their technical specialist to assist you in your selection. I have had excellent success with their product,yes in the garage. You should be able to get results with out spending a lot of money. You don't...
Put parts in vacuum oven @ 250 degrees F for 24 hours. Accurately weight the parts after they come out of the oven, from both mafg. facilities, then perform dimensional checks. Then you will have your answer. You have to get the water out of the part or you can't measure it. Then look @...