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Image: Glass trade in ancient world
Preston Huey  /  Science
The ancient trade in glass, as shown on this map, involved a complex system for transporting ingots of raw glass for processing into ornamental objects including beads, vessels and jewelry.
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Science
updated 7/7/2005 12:10:24 PM ET 2005-07-07T16:10:24

Archaeologists have uncovered for the first time the remains of a Bronze Age glass factory, where skilled artisans made glass from its raw materials. Surprisingly, this factory, which was bustling around 1250 B.C., is in Egypt rather than Mesopotamia, which is generally thought to be where glass was first made.

Glass was extremely valuable during the Bronze Age, so this discovery implies that Egypt may have enjoyed more clout than was previously thought as a producer of this sought-after substance.

The oldest-known glass artifacts of consistently high quality date back to approximately 1500 B.C. These may have been made in Mesopotamia.

“But this is the first place that we have been able to put our fingers on and say, ‘Here it was and this is how they did it,’” said Thilo Rehren of University College London in London. “Until now we have only seen the final products of the glassmaking process, and nothing showing the level of skill and organization in which it was done.”

Rehren and Edgar Pusch from the Pelizaeus-Museum in Hildesheim, Germany describe their findings in Friday's issue of the journal Science, published by AAAS, the nonprofit science society.

A precious commodity
The most common glass objects made during this time period were glass beads and vessels with narrow necks, which may have held perfume or other valuable liquids. They were often made of blue glass, colored to emulate precious stones like turquoise and lapis lazuli, inlaid with white and yellow lines.

Image: Tut's mask
Amr Nabil  /  AP
King Tutankhamun's gold mask, on display at the Egyptian Museum in Cairo, contains glass inlays colored to look like lapis lazuli.
“These were not everyday items. This was absolutely a pharaoh-level of home decoration,” Rehren said.

Most of these objects have been found in Egypt and the region between the Tigris and Euphrates rivers that was once Mesopotamia. They were made in two separate stages.

In the primary production stage, glass was made from plant ash and crushed quartz dust into round disks or “ingots.” In the secondary stage, the ingots were melted down and re-formed into specific objects. Many clues — such as a Late Bronze Age shipwreck off the coast of Turkey that contained a cache of cobalt-blue glass ingots — indicate that the ingots could have been made in one location and then exported to distant locations for the second stage.

“In the last 20 years, we archaeologists have realized this is a serious issue. We can tell the style of the glass objects, but we don’t necessarily know where the glass came from,” Rehren said.

Importer or exporter?
Some indirect evidence has suggested that the Mesopotamians produced glass before the Egyptians did. For example, a victory inscription from an Egyptian pharaoh who had returned from battle claimed he had brought back skilled glassworkers from Mesopotamia. Some Egyptian tomb paintings also show people who appear to be Syrian bringing glass to Egypt, according to Rehren.

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In the late 19th century, Sir Flinders Petrie discovered the remains for Bronze Age glass production in Tell el-Amarna, Egypt, though there was conflicting evidence over whether this was primary or secondary glass production.

Clay tablets at the Amarna site documented a request by Pharaoh Akhenaten for glass to be brought to Egypt, suggesting that glass was not produced in Egypt but only reworked there.

On the other hand, the blue glass ingots found in the Turkish shipwreck matched the dimensions of the glass molds found at Amarna, suggesting that perhaps primary glass production did occur there after all.

Beer jars and special vessels
The artifacts recently discovered at Qantir were clearly used in primary glass production, according to Rehren.

Image: Ceramic jar
Science
Glass was colored and heated in this ceramic vessel, which is about 6.7 inches (17 centimeters) across.
They were found in a large cluster of workshops where hundreds of artisans once worked, also making bronze doors and glazed bricks. The workshops were part of the industrial quarter of a new capital on the Nile Delta that was one of the many building projects undertaken by Ramesses the Great during a peaceful period in Egypt.

In the workshops, the researchers found over 1,000 fragments of various vessels used for producing glass from its raw materials.

Ceramic vessels that may have been recycled beer jars held the plant ash and crushed quartz while they were heated to relatively low temperatures. One of the vessels the researchers found was still full of this semifinished glass.

Image: Ceramic and glass
Science
This jar fragment shows where ceramic material (in red) met raw glass (white). The thin yellow line between the jar and glass is a lime-rich substance that kept the glass from sticking to the jar.
After cooling, the jars were smashed to remove the semifinished glass inside, and then the glass was crushed and washed to remove salt from the plant ash, leaving behind the ash’s key ingredient, soda, bonded to the quartz. The processed powder was then poured through funnels into specialized crucibles, colored (mostly red but also blue and purple), and then heated to higher temperatures to form true glass.

Once the crucible cooled, it contained a glass ingot ready to be sent to another workshop for remelting. Most of the fragments at Qantir have a thin layer of lime on their inner sides, which would have prevented contamination and helped the ingot separate from the container when the crucible was broken apart.

The researchers didn’t find any evidence of the hearth or furnace used, but they hope to continue investigating the site.

In a commentary also published by Science, Caroline Jackson of Britain's University of Sheffield notes that glass was difficult to work, complicated to produce and available in vivid, symbolically significant colors. As such, it was probably a royal commodity exchanged as a gift to enhance power, status and political allegiances.

Any group that controlled the production or consumption of glass would have occupied a powerful political or social position, according to Jackson. Based on the findings at Qantir and the previously excavated site of Amarna, Egypt may have been a major exporter of glass, she writes.

The glass artifacts from Qantir are now staying put in Egypt, however. In the past, so many Europeans removed artifacts from Egypt that the government now bans any export of the ancient material.

© 2013 American Association for the Advancement of Science

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