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Examining the Effect of Relative Humidity on Mammoth Molars

Museum and natural history collections are very sensitive to fluctuations in relative humidity. Because of a high degree of structural anisotropy, mammoth molars are potentially damaged by such fluctuations. Upon excavation, mammoth molars often undergo rapid acclimatization to the ambient RH, with resulting delamination and cracking. Research conducted on mammoth molars by Samantha Fisher in the Art Conservation Program at Queen’s in 2014 found that cracks widen and extend after exposure to 75%RH, that cracks continue to extend after the drop to 35%RH, that cement adsorbs and desorbs faster than enamel, and that Fourier transform infrared spectroscopy shows the presence of hydroxyapatite and water with some carbonate and fluoride substitutions in molars. As the molars used had already undergone humidity cycling, no significant changes to cracks were observed during the experiment.

To further understand the changes occurring during significant drops to low RH, as during the initial excavation and drying of the molars, a single cycle will be undertaken between 11%RH using a saturated lithium chloride solution and 75%RH using saturated sodium chloride solution. Weight changes indicating the adsorption and desorption of water from the teeth will be measured to better understand the internal moisture change, and to identify when the molars have reached equilibrium.

The resulting dimensional changes and crack propagation will be measured using ImageJ analysis software and physically with calipers. This is only one of a very limited number of studies into the effects of relative humidity on natural history collections. A survey of current storage conditions for natural history collections may be undertaken, to identify current practices and possibly propose preventative steps.