I’m not at all familiar with Gesswein’s curing unit, but I would be curious if it’s using LEDs or a UV tube? I have found that I need to cure for longer times than recommended. My curing setup is just a UV (not LED) nail curing unit. I sometimes will leave the pieces to cure for a day or more if I’m not in a rush. If the piece is at all sticky, or slightly soft, it will result in a bad casting, at least in my experience.
I’m also using R&R, but not the one with Bandust. I sometimes will let the piece burnout a little longer at the highest temperature on the Formlabs schedule, but I don’t use their final temperature…I think my final temp is 975°F with a KayaCast vacuum setup, but I’m also casting silver. I haven’t cast gold yet. I have also cast in Keri’s SatinCast, and as far as I’ve noticed, there’s no difference.
I have also found that good ventilation is crucial. I have a little Paragon kiln that has a vent on the top, which I leave open during the entire burnout. I also allow the sprue wax to melt, and at some point I’ll flip the flask over so the button/open side is up. I’ve also had better luck with multiple sprues or a larger sprue. Some of the things that seem like porosity to me I think are more likely related to incomplete burnout and ash residue. On one of my last castings I took the flask out, blew in the hole gently, then returned it for the final ramp down to the casting temp.
I have recently tried the PTFE spray, which seems to work well. I’ve also bought the Neutec “thin” version of their sprue system from Rio that has a fairly large main sprue, and that seems to work well. Perhaps it’s getting more airflow to the pieces. I cast those with perforated flasks, although most of my castings are in small flasks (2, 2-1/2, and 3").
What kind of casting setup are you using? What final temp?