In details: Politics, Portraits, and Love Francesco Bembo, Bianca Capello, and ‘the most beautiful contemporary painting in Venice’ // Kessel, E. J. M. van. (2011, December 1). The social lives of paintings in. Sixteenth-Century Venice. https://scholarlypublications.universiteitleiden.nl/access/item%3A2959515/view

The Portrait of Bianca Cappello, by Scipione Pulzone. The picture note is headed, somewhat misleadingly, I think, "A Portrait Makes a Career". It says "Between October 1585 and 1586, Scipione Pulzone, called Gaetano, ((1540/42 to 1590) painted a portrait of Bianca Capello (1548? t0 1587) that te sitter presented to the Venetian patrician Francesco Bembo (1544–1599). During his sojourn in Florence, Bembo had seen and admired a portrait of Bianca by Plzone, and had asked for a smaller copy of it. A livel correspondence between Bianca and Bembo ensued that discussed the portrait and its production, recording its genesis and an important 'technical' aspect: Pulzone asked the Grand Duchess to provide him with ultramarine, an extremely costly pigment made of lais lazuli. This hint prompted us to use X-ray fluorescece analysis to determine whether Bianca's blue dress really does contain ultramarine; it revealed clear traces of lapis lazuli, allowing us to identify thi spainting as the portrait Bianca gave to Bembo.

In the autumn of 1563, Bianca, the sixteen-year-old daughter of a prominent Venetian patrician family, eloped with her lover Pietro Bonaventuri to Florence. Once there, Bianca asked Francesco de'Medici for protection, and soon they were having an affair that would continue until the end of their lives. Shortly after the death of Francesco's wife, oanna of Austria, in 1578, the tw lovers were secretly married. A year later the official wedding was celebrated in Florence. Bianca was made a daughter of the Republic of Venice and crowned Grand Dchess; Bianca's reputation, which had been ruined by her elopement, was thus rehabilitated, and all of Venice was proud of the city's prominent daughter. In 1586 Bembo presented this portrait to the Venetian public in a formal procession, further bolstering the Grand Duchess's reputation in her home town." http://zmkc.blogspot.ru/2015_08_01_archive.html