Evaluation of the effects of environmental conditions and preventive conservation treatment on painting canvases

The use of preventive conservation measures to assist in retarding the deterioration of painting canvases has been suggested by the Conservation Department of the Tate Gallery [S. Hackney and T. Ernst, The applicability of alkaline reserves to painting canvases, in Preventive Conservation Practice, Theory and Research, Pre-prints of the contributions to the Ottawa Congress, 12–16 September 1994, Ottawa, Canada, p. 223–227]. The reverse sides of paintings are treated with commercially available methoxy magnesium methyl carbonate (MMC) solution. The aim of this paper is to describe how dynamic mechanical thermal analysis can be used to evaluate the effects of this treatment. Measurements are described on modern commercially primed canvas samples [N. Wyplosz, S. Hackney and J.H. Townsend, Studies on the deacidification of canvas with methoxy magnesium carbonate (MMC), in pre-prints of the European Commission research workshop “Effects of the Environment on Indoor Cultural Property”, p. 30.] which show that the MMC treatment does affect the mechanical properties of the treated canvas samples and that dynamic mechanical thermal analysis (DMTA) is a suitable technique for its evaluation. The treatment appears to produce a coating on the samples which acts as a moisture barrier. This was also found to occur for treated historic samples (Battelle process) from loose-lining canvases removed from 19th century paintings. The response of the MMC treated materials to variations in relative humidity has also been studied and indications are that their response to variations in relative humidity differs from those of the untreated canvases