The mold below has cast well over 20,000 Boolits. I've have had to clean Alloy off the blocks twice. So far I haven't rounded any corners but I worry. Even with careful operation I've had Tinning on the underside of the crimp ring near the block faces and the the tips of the grooves on the block faces (503 Clone less than 2% Tin). I was getting small tearouts at the part line and boolits weren't dropping like they should. I carefully cleaned the mold and spent a day treating the blocks with Liver of Sulfur. It was slow and I would have gone for a darker (and more uniform) brown. A a couple thousand Boolits now and no tinning. It did change the thermal characteristics. The brass doesn't suck the heat out of the lead as fast and I'm running the pot 30 degrees hotter (680F) to keep the mold hot enough, but a fair trade for the Teflon finish.
I like the results but I'm sure it could be done better. Anybody have a better patina process for brass?