The green patina and chromatic alterations on surfaces of gypsum plaster casts by Lucio Fontana : multidisciplinary investigations in a case study of contemporary art

Literature reports on Lucio Fontana’s work have focused on the study of the pictorial surface of his paintings. Consequently, to the best of our knowledge, this paper presents the first scientific investigation of gypsum objects made by this artist. These are the gypsum plaster casts made for the construction of the fifth door of the Milan Cathedral, Italy, which were discovered after 60 years, and which showed a green patina and chromatic discolorations. With the aim of understanding the microbiological or chemical nature of the stains, the surfaces of the tiles were investigated by microbiological analysis and analytical techniques including observations by optical, fluorescence and electron microscopy and spectroscopy. The investigated samples showed that the amount of microbiological cells in the stained area was negligible. Chemical analyses allowed the identification of compounds responsible for the chromatic alterations.