 | Glass is common today. In ancient times it was reserved for kings and the elite, valued only slightly lower than silver and gold and about the same as precious gemstones. Archaeologists have found glass beads dating to as early as the third millenium BCE. Glazes and technology date earlier still. In the Late Bronze Age, 1600 to 1200 BCE, the use of glass took off. Glass of those times was opaque and saturated with color. The source of the silica was crushed quartz pebbles, not sand. Ancient glass makers used ash of desert plants, which contain high levels of salts such as sodium carbonate or bicarbonates. The plants also contain lime, calcium oxide, that made the glass more stable. They also added materials to color glass, such as cobalt for dark blue, or lead antimonate for yellow. |