The ancient origins of glass

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Enlarge / This glass fish was found in a fairly modest private house in Amarna, buried under a plaster floor with a few other objects. It may have already contained the ointment.

Administrators of the British Museum

Today, glass is an everyday object on the kitchen shelves. But at the beginning of its history, glass was bling for kings.

Thousands of years ago, the pharaohs of ancient Egypt surrounded themselves with this substance, even in death, leaving archaeologists with superb specimens to discover. King Tutankhamun’s tomb housed a decorative writing palette and two blue headrests made of solid glass that may have once supported the head of sleeping royalty. His funeral mask features blue glass inlays that alternate with gold to frame the king’s face.

In a world filled with buff, brown, and sand hues of more utilitarian Late Bronze Age materials, glass – saturated with blue, purple, turquoise, yellow, red, and white – would have offered the most striking colors other than gems, says Andrew Shortland, an archaeologist at Cranfield University in Shrivenham, England. In a hierarchy of materials, glass would have sat slightly under silver and gold and would have been valued as much as gemstones.

But many questions remain about the prized material. Where was glass first made? How was it worked, colored and distributed in the ancient world? While much is still a mystery, over the past several decades, techniques in materials science and a reanalysis of artifacts unearthed in the past have started to fill in the details.

This analysis, in turn, opens a window into the lives of Bronze Age artisans, traders and kings as well as international relations between them.

The Amarna Letters, clay tablets bearing the cuneiform correspondence of ancient kings and excavated at Tell el-Amarna in modern Egypt, contain references to glass.  An issue of the Canaanite ruler Yidya of Ashkelon (like these pictured) includes one that comments on a glass order for Pharaoh: "As for the king, my lord, having ordered glass, I hereby send to the king, my lord, 30 (
Enlarge / The Amarna Letters, clay tablets bearing the cuneiform correspondence of ancient kings and excavated at Tell el-Amarna in modern Egypt, contain references to glass. An issue of the Canaanite ruler Yidya of Ashkelon (as these illustrated) includes one which comments on a glass order for Pharaoh: “As for the king, my lord, having ordered glass, I send herewith to the king, my lord, 30 (“pieces”) of glass. Besides, who is the dog who would not obey the orders of the king, my lord, the Sun of the sky, the son of the Sun, whom the Sun loves? “

Administrators of the British Museum

Glass of the past

Glass, both ancient and modern, is a material generally composed of silicon dioxide, or silica, which is characterized by its disordered atoms. In crystalline quartz, atoms are pinned at evenly spaced positions in a repeating pattern. But in glass, the same building blocks – a silicon atom combined with oxygen – are arranged upside down.

Archaeologists have found glass beads dating from the third millennium BC. Enamels based on the same materials and the same technology date even earlier. But it was at the end of the Bronze Age (1600 to 1200 BCE) that the use of glass seems to have really taken off, in Egypt, Mycenaean Greece and Mesopotamia, also known as the Near East ( located in what is now Syria and Iraq).

Unlike today, the glass of this era was often opaque and saturated with color, and the source of silica was crushed quartz pebbles, not sand. Intelligent ancients figured out how to lower the melting temperature of crushed quartz to what could be achieved in Bronze Age furnaces: they used the ashes of desert plants, which contain high levels of salts such as sodium carbonate or bicarbonates. Plants also contain lime, calcium oxide, which makes the glass more stable. Ancient glassmakers also added materials that give color to glass, such as cobalt for dark blue or lead antimonate for yellow. The ingredients melted into the cast iron, providing chemical clues that researchers are looking for today.

“We can start to analyze the raw materials that went into the production of glass and then suggest where in the world it came from,” says materials scientist Marc Walton of Northwestern University in Evanston, Illinois, co-author of ‘an article on materials. scientific and archaeological artifacts and works of art in the 2021 Annual review of materials research.

But these clues have only led researchers so far. When Shortland and his colleagues investigated the origins of glass about 20 years ago, glass from Egypt, the Near East and Greece appeared to be similar chemicals, difficult to distinguish based on techniques available to the world. era.

The exception was blue glass, thanks to the work of Polish-born chemist Alexander Kaczmarczyk who, in the 1980s, discovered that elements such as aluminum, manganese, nickel and zinc combine with cobalt. which gives the glass an abyssal blue tint. By examining the relative amounts of these, Kaczmarczyk’s team even tracked the cobalt ore used for the blue coloring to its mineral source in specific Egyptian oases.


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