Proposed methods for determining the brick moisture expansion that has occurred during service and for predicting future moisture expansion depend on the reversibility of moisture expansion. Tests were made to evaluate the extent and circumstances of reversibility. It was found that the moisture expansion of some brick materials can be removed by heating the specimens to 400 to 500°C. In other cases the reversibility was poor. Kaolinitic clays recovered better than 95% of their moisture expansion, whereas sandy bentonitic recovered as little as 12%. The presence of lime particles produced high expansions which were non-reversible in some instances. The temperature of reheating is important. Reheat temperatures that cause additional sintering will give values higher than the actual expansion. Reheating above the quartz inversion temperature will reduce or even indicate negative expansions. Heating to 110°C will remove part of the expansion, but heating to 400 to 500°C is needed to remove all the expansion of those substances with high reversibility. -- AATA