The purpose of this technical bulletin is to explain the use of silica gel, how it controls relative humidity, and how it is conditioned for use and maintained. The specific topics dealt with are: the problems of display case leakage, the requirements of a humidity buffering agent and how silica gel fulfills these, the various steps in the process of conditioning silica gel, the positioning of silica gel in the display case, and the maintenance of a silica gel buffered case.