Evaluating the environmental response of Rembrandt’s The Night Watch (1642) using water sorption experiments and diffusion modelling

Rembrandt’s The Night Watch (1642) has been wax-resin lined, which involved attaching a new canvas to its reverse using a beeswax-resin mixture to achieve structural stabilisation and shielding against environmental humidity. We investigated the effect of wax-resin lining on water transport in The Night Watch using a one-dimensional, multi-layered water transport model based on ideal diffusion. Model input parameters were estimated using dynamic vapour sorption experiments. The paint layer response in the environmental conditions of the BIZOT Green Protocol was evaluated. During the fastest allowed RH fluctuation in BIZOT, water concentration in the paint layer of wax-resin lined paintings only reached 30% of the maximum concentration at static RH conditions (60% RH). Furthermore, we show that the water sorption capacity of the wax-resin adhesive of The Night Watch increased after ca. 50 years of natural ageing. Modelling results indicated that the effect of this increase on the overall response is minor.