The Lady with an Ermine – Portrait of Cecilia Gallerani: Research into Leonardo da Vinci’s painting materials and techniques

The Lady with an Ermine is one of the greatest masterpieces by the Italian artist Leonardo da Vinci from around 1489-1490, depicting Cecilia Gallerani, most likely at the time when she was the mistress of Ludovico Sforza, Duke of Milan. This painting belongs to a group of four portraits of women painted by Leonardo along with the Mona Lisa, Ginevra de' Benci and La Belle Ferronnière. It was acquired by Prince Adam Jerzy Czartoryski around 1800 in Italy. In 2012, a group of conservators and scientists from the National Museum in Krakow in collaboration with experts from various institutions in Poland and abroad conducted the sixth research campaign on the painting focusing on its technological aspects. Various techniques were applied to study the materials and methods employed by Leonardo, including technical photography, X-radiography, micro X-ray fluorescence spectrometry. Physico-chemical analyses allowed to identify characteristic pigments employed by Leonardo da Vinci such as vermilion, iron-based earth pigments, lead-tin yellow, lead white, and ultramarine. The background was overpainted in black, most likely before its sale, in the 18th century. The original background most likely consists of an underlayer layer showing slight grey tone modulations obtained using iron oxide or hydroxide mineral earths. The absence of copper-based pigments in the background does not validate the hypothesis of an existing painting hidden under the black repainted zone. A dominance of lead white in brighter parts of the painting was noted, while tonal transitions were achieved using thin layers of an iron-based glaze in the sfumato technique.