1 INTRODUCTION

Fluctuations in ambient temperature and relative humidity and the subsequent deleterious effects on artworks is an accepted and well-studied subject that has generated numerous bibliographies (Thompson 1964; Padfield 1966; Hackney 1990; Michalski 1991; Skalka 1991). Maintaining the physical stability of artworks is essential to their preservation. The demand for traveling exhibitions escalates concern for the artworks' stability. For a painting on a wood support, these fluctuations can yield changes in the moisture content of the wood itself, causing shrinkage and expansion. These changes, in turn, can weaken the adhesion between the paint and/or ground layers and the wood support, resulting in paint loss. Controlling the moisture content of the wood panel and thereby minimizing this process has been the goal of many conservation practices.

The need to control moisture content has led to the development of systems for protecting panel paintings in sealed, climatically stable microenvironments used in transit and/or during exhibition in what may be climatically unstable external environments (Sack and Stolow 1978; Ramer 1984; Bosshard 1990; Hackney 1990; Richard 1994; Wadum forthcoming). Museums often use stationary, climate-controlled vitrines in-house, and borrowing institutions can provide them as part of a loan requirement. Even with proper packing and transport, however, such a requirement does not ensure protection during transfer of the artwork into or out of the vitrine, nor does it address the possible differences between the initial environment and the new preconditioned one. Further, though the design and construction of the in-house vitrine may be close to ideal and the internal environment carefully monitored, responsibility rests entirely on the borrowing institution.