Explains the means by which buffered silica gel and saturated salt solutions regulate relative humidity within a closed exhibition case. A comparison is made between the two approaches to relative humidity control in terms of volume of space needed to accommodate the buffer, effectiveness, and frequency and convenience of maintenance. Calculating the necessary amount of buffered silica gel or saturated salt solution is demonstrated using magnesium nitrate as an example. Air circulation problems and air pollution from salt solutions are discussed. -- AATA