Honed Jerusalem Limestone tiles that severely pitted in a residence after only a few months of service were left undisturbed for several additional months in a warm, moist environment. An abundant white-coloured substance formed on the surface of the limestone tiles and within the natural limestone structures disrupting the fabric of the stone and contributing to additional spalling and eventual disintegration. The distribution of this white “efflorescence” appeared to have a gradient broadly emanating from a substantial cocktail bar housing an ice-maker. Spalled fragments of the limestone tiles exhibited an unusual, pungent chemical odour which indicated the involvement of a volatile organic compound (VOC). Several varieties of construction materials (including certain types of wood) contain such compounds and a direct link has been established historically to the disintegration of calcareous materials in museums.
The white, fibrous, crystalline growth on the Jerusalem limestone floor tiles of the residence was determined to be calcium acetate hydrate. This substance has been known for over a century to form on the surface of, and eventually totally replace, calcareous biological specimens in museums. A similar but compositionally slightly different substance has been reported as forming on archaeologically significant calcareous terracotta vases. In all instances where calcium acetate hydrate has formed there is a common link between the presence of volatile organic compounds such as acetic acid and formaldehyde, available moisture, and protracted elevated temperatures. In all previously reported occurrences the source of the acetic acid and/or formaldehyde has been type of enclosure. Wood such as premium oak emits VOC’s, and both chipboard and craftwood are manufactured with glues that emit substantial amounts of VOC’s (especially within about 6 months of manufacture) of the type that has the potential to cause the efflorescence. Prolonged moisture will affect the integrity of the manufactured wood products and some of the VOC’s are likely to be mobilized in solution. This is supported by the presence of a pungent odour of ?formaldehyde within broken limestone tile fragments several meters from the bar. The application of acetic acid-based fluids at any stage (e.g. to remove the polished surface, to clean up after tiling, or as a general cleaning product) could also introduce a source of VOC’s by the reactivation (under appropriate conditions) of any residual fluid absorbed by the limestone tiles. Additional interactions might also occur between the VOC’s and any salt present in the calcareous limestone.