Os estratos preparatórios das obras do pintor eborense Francisco João (activo entre 1563 e 1595)

Abstract

This article presents the material and technological data obtained from the study of the preparatory layers of 32 panel paintings produced in the Alentejo region, southern Portugal, and attributed to the painter Francisco João, active between 1563 and 1595. The investigation was based on the macroscopic observation of the paintings and on the analysis of the preparatory layers with several analytical methods. The grounds are white and composed of a single layer of “gesso grosso”, mainly anhydrite mixed with a little calcium sulphate dihydrate, calcite and dolomite. The priming layers, found in six groups of paintings, are medium-rich and carry a few red (minium or vermilion) or ochre and brown (possibly umber) pigments. Non painted edges and barbs were found in the majority of paintings as well as the imprints of the tools used to spread and polish the preparatory layers.