Some secrets of Renaissance Venetian opaque red glass revealed by analyses and glassmaking treatises

Opaque copper red glass has been produced since the birth of the glassmaking technology. Since the first/second c. AD the so-called red brown glass was produced and was constantly made up to nowadays. Despite several analytical studies, many technological aspects of this particular glass are still unclear. Opaque red brown glass was widely made also in Venice. Samples of Renaissance Venetian glass were analysed and abundant historical sources of this period including recipes of Venetian glassmakers are available. This combination of analyses and texts represents a unique opportunity to shed light on the production technology of red brown glass. The aim of this work is to better understand some aspects of this glass, such as the raw materials used, the glassmaking procedure, the control of the final colour, through a comparison between chemical analyses of Renaissance Venetian samples and the indications of historical sources. The information obtained for Venetian glass could be useful for the interpretation of the technology of red opaque glass made in other places and periods for which specific written documents are lacking.