The Technology of Venetian Girasole Glass

Abstract

Venetian glass has long been admired for its quality workmanship and overall visual appearance. Beginning in the 17th century, Venetian glassmakers at Murano made a glass, in imitation of naturally occurring opal, called girasole. The historical and cultural background of this unique glass was examined using information from Venetian archival sources. An assortment of Muranese recipes for girasole spanning almost 150 years provided additional data regarding the raw materials used by Muranese glassmakers in the 17th-19th centuries. These recipes also allowed the authors to evaluate the continuing evolution of the Venetian glass industry. A sample of Venetian girasole glass was analyzed using x-ray diffraction, inductively coupled plasma-atomic emission spectroscopy, scanning electron microscopy, and transmission electron microscopy. The compositional information obtained from these analytical techniques was correlated to the various recipes for girasole glass as well as to glass properties that would have been behaviorally significant to a glassmaker at Murano. Finally, the analyses indicate that small crystallites of a lead-arsenate compound were nucleated and grown in the glass to achieve the desired visual effects. These crystallites cause Rayleigh scattering of the light, thereby producing Tyndall blue colors.