The environmental effects of temperature and relative humidity on the mechanical response of paintings and photographs were examined using numerical methods and computer analysis. The basic mathematical approach is introduced that defines the material parameters necessary to conduct such an analysis. Methods of determining the material and dimensional properties of materials with comments on the effects of increasing measurement accuracy are discussed. Using measured material properties for paintings and photographs, complete computer analyses were conducted that modeled the physical response to changing temperature and relative humidity. The calculated results were compared to experimental test specimens subjected to similar environmental variations.