Experimental criticality measurements have been made on assemblies of plutonium metal to design a crucible that can safely melt up to 12 kg of plutonium. In addition, in situ experiments on two prototype crucibles and furnace setups confirmed the 12-kg capacity. These crucible designs were responsible for a considerable savings in initial capital and operating expense for a new plant. A comparison of Monte Carlo calculations and experimental measurements indicated that the calculational method is sufficiently accurate to be used in future crucible designs, rather than a series of critical mass measurements. The cost for a calculational study is less than 2% of the cost of an experimental study.