Some questions about thermal shock and the use of boiling stones are tested in a series of experiments in which rounded flint stones are used to heat food in ceramic vessels. A number of problems with the pot boiling stone technique are noted, including breakup of flint in the food. In contrast to expectations based on work of others, no problems were noted in using quartz sand tempered ceramics for cooking on an open fire. Neck and rim shape were found to be important to a vessel's utility in cooking. In sum, it seems unlikely that the technique of boiling water with heating stones would have been used with ceramics, considering most ceramic vessels are well suited for direct placement on the fire.