Determination of allowable RH fluctuations

Abstract

A brief introduction to work undertaken by the Smithsonian Institution to determine the allowable range of relative humidity fluctuations that museum objects can tolerate without mechanical damage. The authors present stress-strain curves at various relative humidities for cottonwood, as well as plots of relative humidity values which produce yielding or failure in restrained cottonwood as a function of equilibrium relative humidity. They do not provide measurements and calculations for other materials, though the results are comparable. The authors conclude that the allowable fluctuation is a function of the relative humidity to which the object is equilibrated and that the relative humidity with the maximum allowable fluctuation varies with material. Though the allowable fluctuations can be quite different for different materials, all the allowable fluctuations are larger than those generally presently recommended.