This study demonstrates experimentally that for a fixed microwave input power, the steady-state temperature for microwave "caskets" (specimen enclosures) can vary significantly as the casket geometry changes. Also, the steady-state casket temperatures are very similar for caskets with and without an included specimen, as long as the specimen's volume and mass are small com pared to the casket's volume and mass. In addition to the experimental work, a simple model is presented that describes the variation in steady-state temperature as a function of casket geometry. The model also describes how the steady-state casket temperature scales with microwave input power level. For the single-mode microwave cavity operated at 2.45 GHz that is used in this study, the steady-state casket temperature at 600 Watts of input power ranged from 1112 degrees C to 1519 degrees C as the casket geometry changed for caskets composed of porous zirconia cylinders with aluminosilicate end plates.