The Tomb of Nefertari, no. 66, Valley of the Queens, is an internationally known monument of historic and artistic importance; it is considered one of the most beautiful of the Royal Egyptian tombs. The fragility of its plaster along with its ubiquitous sodium chloride crystals and microcrystals have complicated its conservation and restoration. In order to determine the optimum pathway for its conservation, the physicochemical processes which occur now in this tomb must be well understood. To improve this understanding, samples of plaster taken from the tomb have been analyzed using differential scanning calorimetry and x-ray diffraction and have been shown to be fully dehydrated; previous findings suggest that this is not the case in all contemporary royal tombs. Although we are not aware of any kinetic study of gypsum dehydration in the solid state, the presence of anhydrite in the Tomb of Nefertari suggests that the CaSO₄ . 2H₂O right arrow CaSO₄ + 2H₂O reaction is catalyzed. It is reasoned that finely dispersed sodium chloride crystals act as effective catalysts in this reaction.