Assessing the pH and DP of canvasses with NIR spectroscopy

Abstract

The canvas support in easel paintings is composed mainly of cellulose. One of the main degradation paths of cellulose is acid-catalysed hydrolysis, which means that in an acidic environment (low pH), its degradation proceeds at a faster rate (Strlič et al., 2005). The main effect of acid-catalysed hydrolysis is the breaking up of the polymer chains, measured by the “Degree of Polymerisation” (DP). The lowering of the DP value implies a lower mechanical strength of the textile (Scicolone, 1993), and thus this parameter can be used to monitor degradation. Knowing these two parameters can, therefore, be very informative regarding the condition of the canvas support.