First thing I can see wrong with your setup is the pan you have your blank set in. A 4 sided deep pan like that reflects and consentrates the heat back up toward your blank like a reflector oven would do. 2ed you need air to circulate around your blank. Cut a V groove in two wooden blocks to hold your rod and blank off the surface. You should also use the metal rack to keep your blank centered as much possable inside your oven and to allow air flow. 3ed Tin foil under and over your blank to reflect any hot spots away from your blank. 4th Go to Walmart and buy a oven thermometer, the stand up type, ($10) and place it inside the oven. Preset dials are never on the money. When your oven temp. reaches the degree you want, mark your dial for that setting. And last, I think 275 degrees is a little high, and unless you are doing a thick casting, 30 minutes is to long. I bake my polymar clay pen blanks at (true) 250 degrees for 15 minutes and remove them hot and submerge in cold water. Now you can dry them off and bring them directly to the lathe and turn. If they seem a little soft, return to the oven for another 5 minutes or so. I do a lot of inlays that require 2 heating cycles, one for the base color, and one for the inlay itself. Once your first heating cycle has been reduced back to room temp, and your inlay has been applyed, another 15 minutes of bakeing does not harm the blank. Jim S