Barry Knight and David Thickett
The response of a piece of historic furniture exposed to natural fluctuations in the ambient temperature and relative humidity (RH) has been determined, using a minimally intrusive displacement sensor. Changes in the width of a previously existing crack were monitored and were found to follow changes in relative humidity closely. The cross-correlation function of the crack width and the RH was calculated, and showed that the crack width followed the RH with a time lag of approximately 41 hours. The object hardly responded at all to more rapid fluctuations.