This is how I made my curing box. I had a friend that had an old cube refrigerator that worked too well. It always got things too cold and froze them. Plus his wife didn't want it anymore, so I asked if I could take it off there hands. This was a great deal. I got two tools out of one item for free, a curing box and a vacuum pump. I started by carefully removing the compressor assembly out of the unit after the Freon was recovered by a friend of mine. Once the unit was out, I removed all the tubes and wires that I could without tearing up the inside of the box. Once all the compressor pieces were removed I cleaned it inside and out. I purchased a small ceramic heater with a thermostat controller and built in overprotection circuit at Wal-Mart for $17.00. I modified this unit so the fan would run all the time. I also enclosed the contacts so they would not create a spark and possibly ignite any gases that may have accumulated in the curing chamber. I had to drill a one inch hole in the back to get the plug through so I could plug it in. This hole doubles as a vent hole. Then a drilled a small hole at the top of the box for a thermometer to be placed into the box for oven readings. As you can see, my mixing bowl fits with all kinds of room left over. Since I plan on casting grains into the pre-made tube sizes, I should have plenty of room for even big M motor castings. I'm working on a different way to sense and control the temperature in the box.