Pennsylvania German sulfur-inlaid furniture: characterization, reproduction, andageing phenomena of the inlays

Abstract

Eighteenth-century Pennsylvania German furniture inlaid with an ivory-colouredmaterial was first mentioned in the art historical literature in 1958. Since thattime, there has been substantial confusion about the composition of these inlays,the source of their colour and their method of manufacture. In 1977, a number ofthese inlays were identified as an unspecified allotrope of sulfur. Eighteen yearslater, a second type of ivory-coloured eighteenth century furniture inlay that didnot contain sulfur was identified, and a method of reproducing the sulfur inlays bypouring molten sulfur into an incised decoration was demonstrated. Thereproductions were structurally successful, containing the air bubble inclusionsthat are observed in the eighteenth-century inlays, but they were thebright yellow colour that is characteristic of α-S8,the allotrope of sulfur typically observed at ambient temperatures. Fiveeighteenth-century Pennsylvania German ivory furniture inlays werecharacterized by x-ray diffraction (XRD), Fourier transform infraredspectroscopy, scanning electron microscopy energy-dispersive x-raymicroanalysis, energy dispersive x-ray fluorescence, colorimetry and gaschromatography–mass spectrometry to identify their compositions. Four of theeighteenth-century inlays were found to be pure α-S8.The inlays were further characterized by colorimetry and non-spinningDebye Scherrer XRD to identify the source of the ivory colourobserved in the eighteenth century α-S8.Data from these experiments suggest that the ivory colour is caused by a particlesize decrease of the sulfur that may result from repeated climatic cycling. Thiswould occur over the course of 200 years spent in an uncontrolled environment,and artificial ageing experiments will be used to determine if it is due to the lowthermal conductivity of sulfur, a property responsible for the macroscopiccracking and spalling of sulfur in natural history collections. The composition of asulfur inlay repair and an eighteenth-century non-sulfur ivory-coloured inlay arealso presented, along with their roles in the common misconceptions about sulfurinlay.