Description
Lead has been used to make crystal glass since ancient times. Glasses with lead oxide content first appeared in Mesopotamia, the birthplace of the glass industry. The earliest known example is a blue glass fragment from Nippur dated to 1400 BC containing lead. Glass is mentioned in clay tablets from the reign of Assurbanipal (668-631 BC), & a recipe for lead glaze appears in a Babylonian tablet of 1700 BC. Lead glass also occurs in Han-period China (206 BC - 220 AD). There, it was cast to imitate jade, both for ritual objects such as big & small figures, as well as jewellery & a limited range of vessels. Since glass first occurs at such a late date in China, it is thought that the technology was brought along the Silk Road by glassworkers from the Middle East. in medieval & early modern Europe, lead glass was used as a base in coloured glasses, specifically in mosaic tesserae, enamels, stained-glass painting, & bijouterie, where it was used to imitate precious stones. Several textual sources describing lead glass survive. in the late 11th-early 12th century, Schedula Diversarum Artium (List of Sundry Crafts), the author known as "Theophilus Presbyter" describes its use as imitation gemstone, & the title of a lost chapter of the work mentions the use of lead in glass. The 12-13th century pseudonymous "Heraclius" details the manufacture of lead enamel & its use for window painting in his De coloribus et artibus Romanorum (Of Hues & Crafts of the Romans). This refers to lead glass as "Jewish glass", perhaps indicating its transmission to Europe. A manuscript preserved in the Biblioteca Marciana, Venice, describes the use of lead oxide in enamels & includes recipes for calcining lead to form the oxide. Lead glass was ideally suited for enamelling vessels & windows owing to its lower working temperature than the forest glass of the body. Antonio Neri devoted book four of his L'Arte Vetraria ("The Art of Glass-making", 1612) to lead glass. in this first systematic treatise on glass, he again refers to the use of lead glass in enamels, glassware, & for the imitation of precious stones. Christopher Merrett translated this into English in 1662 (The Art of Glass), paving the way for the production of English lead crystal glass by George Ravenscroft. George Ravenscroft (1618-1681) was the first to produce clear lead crystal glassware on an industrial scale. The son of a merchant with close ties to Venice, Ravenscroft had the cultural & financial resources necessary to revolutionise the glass trade, setting the basis from which England overtook Venice & Bohemia as the centre of the glass industry in the eighteenth & nineteenth centuries. With the aid of Venetian glassmakers, especially da Costa, & under the auspices of the Worshipful Company of Glass Sellers of London, Ravenscroft sought to find an alternative to Venetian cristallo. His use of flint as the silica source has led to the term flint glass to describe these crystal glasses, despite his later
