The earliest known glass objects were beads, perhaps initially created as accidental by-products of metalworking (slags) or during the production of faience, a pre-glass vitreous material made by a process similar to glazing. Although there is some evidence of glass since the 3rd millennium BC (Peltenburg 1987, 5-30; Lilyquist and Brill 1993, 5), the first significant finds of man-made glass are in Egypt and the Near East around the end of the 15th century and into the 14th century BC. The objects associated with glass at this time are mainly opaque and/or coloured. That some of the words for glass in the Amarna letters are Hurrian or Akkadian (Oppenheim 1973) hints that early glass was imported to Egypt, perhaps brought over by Thutmosis III (1479-1425 BC) (Nicholson 2006; Jackson 2018).
Until recently, there was neither clear physical evidence of Egyptian glass in Mesopotamia nor Mesopotamian glass in Egypt (Walton et al. 2009; Rehren and Freestone 2015). However, Varberg et al. (2015; 2016) have demonstrated that glass of Mesopotamian origin reached Egypt and Europe. Nonetheless, just as the innovation spread and became established throughout Egypt and the Near East, after around 1250 BC the number of glass finds dramatically drops, indicating that glass production had massively declined by the end of the 2nd millennium (Moorey 1994, 198; Shortland 2012, 169-73; Rehren 2018). As Shortland (2016, 95) highlights, 'There therefore remains a short flowering of this technology in the third quarter of the 2nd millennium BC, and then it disappears almost completely'.
Sudden transitions between material types in the archaeological record are often attributed to changes in the accessibility of the raw materials, or the material being replaced by other materials that are easier to process and/or provide better functional properties. However, issues surrounding accessibility are unlikely to be pertinent to glass per se, as all early glass appears to be of the same compositional type (soda-lime-silica), with glass becoming a truly utilitarian functional material only after the invention of glass blowing (c. 50 BC). This could suggest that the low amounts of glass recovered after c. 1250 BC (Shortland 2016, 95), with glass production not resuming for about five centuries, was because glass objects were no longer in demand. It is proposed here, however, that the disappearance of glass at the end of the Late Bronze Age (LBA) was not because glass itself went out of fashion but because the raw material precursors required to render the glass opaque and produce the colour combinations desired from glass objects were no longer readily accessible. In particular, it is proposed that the disappearance of cobalt blue, a major colourant in early glasses, is directly related to the exhaustion of native silver and dry (also known as siliceous or quartzose) silver ores at the end of the LBA, affecting glass production across the ancient world.
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