Preliminary Study on the Biodeterioration of Canvas Paintings from the Seventeenth Century by microchiroptera

This work focuses on the peculiar alterations found on various canvases from the refectory of the Carthusian monastery in Granada. The works studied were by the Baroque painter from Granada, Juan Sanchez-Cotin. During the study, the biological origin of these alterations was confirmed as being due to the products excreted by vespertilionid chiroptera, which roost in the summer on the corner braces of the stretchers of these paintings. These excretory substances have seriously deteriorated the images, causing blank areas and even total loss of the canvas, preparatory layer and pictorial strata. During restoration, it was confirmed that the excretory material of these bats continued to be active and hampered correct application of conservation treatments. Consequently, it proved necessary first to study and treat the excretions, which sharply lowered the pH of canvases. The zones impregnated with urine, extending from the upper to the lower braces, were neutralised, thereby stabilising the weak areas and providing satisfactory conditions for subsequent restoration treatments.