Grisailles: Reconstruction and characterization of historical recipes

This study aims to contribute to the rediscovery of old technologies in the art of stained-glass painting with grisaille, a dark color paint, used to create contours and shadows, produced by mixing ground lead-based glass with coloring agents such as iron and copper. The reproduction of selected recipes belonging to five different treatises, dated from the 10th to the 19th century was designed to study the evolution of the composition and production technology of this historical paint and the repercussions of this development on the thermal compatibility of the grisailles with the glass substrates.The results indicate that the raw materials and the production methods remained roughly the same throughout the centuries. However, the chemical composition of the lead-based glass and the source of colorants (burned metals were replaced by ochre's and earths in the 19th century) did change. These modifications impacted on the morphology of the grisailles paint layers towards a greater homogeneity. The results also reveal low thermal compatibility between these two materials, associated with both the composition and the morphology of the grisaille.