In an effort to unlock the riddle of how it was that the paintings of Venetian Renaissance masters had a "special glow" about them, Barbara Berrie, senior conservation scientist at the National Gallery of Art, trained an electron microscope on works by Tintoretto and Lotto. The secret revealed: glass mixed into the pigments.
Barrie had developed the hypothesis after Louisa Matthew, an art historian at Union College in Schenectady, N.Y., did some sleuthing around in the Venetian State Archives. There she found some curious inventory records dating to 1534 taken from the shop of Domenico de Gardignano, a Venetian color merchant. The documents suggested that some of his pigments had contained ground glass, something modern scholars had absolutely no clue about.
I guess if anyone were to use glass innovatively this way, it would be the Venetians, given their mastery of art glass. The pre-Venetians -- the Roman subjects of places like nearby Aquilea -- were likewise glass geniuses, and the speculation is that they brought their secrets to the lagoon when they fled the mauraders in the early part of the first millenium. Perhaps glass in pigments was one of them.
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