THE COLD WALL PROBLEM AS A CAUSE OF ACCELERATED AGING OF PAINTINGS

Abstract

The general restoration of the Kunsthistorisches Museum in Vienna and the installation of new air-conditioning in the picture gallery led to reconsideration of the current practice of climate control with respect to paintings hanging on outside walls. Pictures either in direct contact with the wall or placed too close to outside walls are more exposed to daily and seasonal cycles of warming and cooling than paintings on inside walls. Pictures on 'cold walls' suffer from condensation and the effects of increased humidity between wall and painting. The lower surface temperature causes capillary condensation which means that water in liquid form is deposited at boundary surfaces. This causes varnish to bloom or to blanch. Schaible [1] has demonstrated that most deformation mechanisms and symptoms of deterioration are the result of uncontrolled sorption cycles and permeation. Berger [2] found that canvas paintings suffer 25-50% strain differences with temperature differences of only 2°C. These processes are also brought about by short-term variations in temperature and relative humidity due to faulty regulation of climate control systems but they are intensified in paintings hanging on cold walls. The cold wall phenomenon is exemplified by measurements of the surface temperature of three paintings hanging on outside walls, made by the author in 1990, before restoration of the picture gallery commenced.