I hadn't cast in a few years and today was teaching my SOL the basics. I had a baggie of sawdust that had been sitting under the bench and I added a small fistful to my bottom pour, heard a pop and got a few splatters on my welding shirt. Wasn't a whole lot to it, this time, but I guess the moral of the story is you never know when and where and how viciously she'll show up. Took the sawdust inside and dried it out in the oven, cured the problem. Was glad the SOL was standing there as he thought I was crazy when I told him to show up this morning in full combat gear. Reinforced my point.