Islamic glass

The influence of the Islamic world to the history of glass is reflected by its distribution around the world, from Europe to China, and from Russia to East Africa. Islamic glass developed a unique expression that was characterized by the introduction of new techniques and the innovation of old traditions.

Islamic glass did not begin to develop a recognizable expression until the late 8th or early 9th century AD, despite Islam spreading across the Middle East and North Africa during the mid-7th century AD. Despite bringing enormous religious and socio-political changes to the region, this event appears to have not drastically affected the day-to-day workings of craft industries, nor did it cause "extensive destruction or long-lasting disruption". The Roman (Levant and Egypt) and Sassanian (Persia and Mesopotamia) glassmaking industries continued in much the same way they had for centuries earlier. Following the unification of the entire region, the interaction of ideas and techniques was facilitated, allowing for the fusion of these two separate traditions with new ideas, ultimately leading to the Islamic glass industry. Roman glassmaking traditions that are important in the Islamic period include the application of glass trails as a surface embellishment, while stylistic techniques adopted from the Sassanian Empire include various styles of glass cutting. This may have developed out of the long-standing hardstone carving traditions in Persia and Mesopotamia. In regards to glass-making technology, tank furnaces used in the Levant to produce slabs of raw glass for export during the Classical Period were used during the Early Islamic Period in the same region until the 10th or 11th centuries AD.

During the first centuries of Islamic rule, glassmakers in the Eastern Mediterranean continued to use the Roman recipe consisting of calcium-rich sand (providing the silica and lime) and mineral natron (soda component) from the Wādi el-Natrūn in Egypt, and examples of natron-based Islamic glass have been found in the Levant up to the late 9th century AD. Archaeological evidence has shown that the use of natron ceased, and plant ash became the source of soda for all Islamic glass in the following centuries. The reasons for this technological transition remain unclear, although it has been postulated that civil unrest in Egypt during the early 9th century AD led to a cut-off in the natron supply, thus forcing Islamic glassmakers to look for alternate soda sources. Evidence of experimentation with the basic glass recipe at Beth She'arim (modern Israel) during the early 9th century AD further supports this argument. A glass slab made from a tank mold from the site contained an excess amount of lime, and may be the result of mixing sand with plant ash. Although the raw glass would have been unusable due to its composition, it does suggest that at this time, Islamic glassmakers in the Levant were combining aspects of Sassanian and Roman traditions in an effort to solve the problem created by the lack of access to mineral natron. The use of plant ash, specifically from halophytic (salt-loving) plants, which were plentiful in the Middle East due to the climate, was well known in Persia and Mesopotamia. It undoubtedly would not take long for the glassmakers in the Near East to correct their manufacturing errors and begin using the plant ash-based recipe used further east.

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