I cast for years in my little outdoor shop in the 30's and 40's, much better than when it is 100 out side. So, the thermostats don't work well or to the same temperature due to air flow, Ian is right in that I had to cast with the door open and window open. I only had iron moulds in those days and 4 cavity Lyman's worked just fine. Timing was critical as a few seconds too long and I needed the mallet to open the plate. Used a milking heater to blow on my pac's and stayed warm enough to cast for a couple of hours, after an hour heating time for the pot. My biggest issue was to keep condensation off the ingots to recharge the pot. Ric