You must post-cure all stereo lithography resin parts properly. Properly means "oxygen free". This is especially important for all directly castable "resins". You can purchase a very expensive curing chamber that pumps inert gas into the curing chamber or you can modify your curing unit and pump inert gas into that during curing. Gas can be expensive, especially if you forget to turn it off.
Your other option is to use our React-Shun Curing Gel instead. Put your parts into a small clear zip lock bag (ring bag) or a small optically clear glass container (Pyrex bowl) and pour the curing gel liquid in on top of them. Squeeze the air bubbles out of the gel in the plastic bag and zip it up or weigh down the parts in the bowl. The goal is to get the parts completely covered under the gel and away from any oxygen. If you use the bag method, rinse off the bag with tap water, if you want to, in order to get any gel that may have squeezed out of the bag. Put the bag into the curing box and cure on one side for about 15 minutes, then flip the bag over and cure on the other side for the same. 15-30 minutes in the curing box should be sufficient for most parts. Very thick parts may require more time. If you are using a bowl, weigh the parts down so they sink under the gel. Resin parts will float in the gel otherwise.
React-Shun Curing Gel is a very safe, non-toxic, reusable material. Simply remove the parts from the gel, drip off as much as you can back into your container, and rinse off your parts with tap water. After rinsing and drying your parts, apply your feed sprues to your parts before you dip them into our other product, "React-Shun RP barrier dip" in preparation for direct casting or molding. Only one dip is sufficient for molding in low temperature vulcanized rubber. 3 - 5 dips with a light compressed air blow off will be required for direct casting in gypsum bonded investment. 4 dips is a good average.