The ancient origins of glass

Right this moment, glass is bizarre, on-the-kitchen-shelf stuff. However early in its historical past, glass was bling for kings.

Hundreds of years in the past, the pharaohs of historic Egypt surrounded themselves with the stuff, even in loss of life, leaving beautiful specimens for archaeologists to uncover. King Tutankhamen’s tomb housed an ornamental writing palette and two blue-hued headrests product of stable glass that will as soon as have supported the top of sleeping royals. His funerary masks sports activities blue glass inlays that alternate with gold to border the king’s face.

In a world stuffed with the buff, brown, and sand hues of extra utilitarian Late Bronze Age supplies, glass—saturated with blue, purple, turquoise, yellow, pink, and white—would have afforded essentially the most hanging colours aside from gems, says Andrew Shortland, an archaeological scientist at Cranfield College in Shrivenham, England. In a hierarchy of supplies, glass would have sat barely beneath silver and gold and would have been valued as a lot as treasured stones have been.

However many questions stay in regards to the prized materials. The place was glass first usual? How was it labored and coloured and handed across the historic world? Although a lot continues to be mysterious, in the previous couple of a long time supplies science strategies and a reanalysis of artifacts excavated previously have begun to fill in particulars.

This evaluation, in flip, opens a window onto the lives of Bronze Age artisans, merchants, and kings in addition to the worldwide connections between them.

Glass from the previous

Glass, each historic and trendy, is a fabric often product of silicon dioxide, or silica, that’s characterised by its disorderly atoms. In crystalline quartz, atoms are pinned to frequently spaced positions in a repeating sample. However in glass, the identical constructing blocks—a silicon atom buddied up with oxygens—are organized topsy-turvy.

Archaeologists have discovered glass beads courting to as early because the third millennium BCE. Glazes based mostly on the identical supplies and expertise date earlier nonetheless. But it surely was within the Late Bronze Age—1600 to 1200 BCE—that using glass appears to have actually taken off, in Egypt, Mycenaean Greece, and Mesopotamia, additionally referred to as the Close to East (situated in what’s now Syria and Iraq).

In contrast to right this moment, glass of these occasions was usually opaque and saturated with colour, and the supply of the silica was crushed quartz pebbles, not sand. Intelligent ancients discovered how one can decrease the melting temperature of the crushed quartz to what could possibly be reached in Bronze Age furnaces: they used the ash of desert crops, which comprise excessive ranges of salts reminiscent of sodium carbonate or bicarbonates. The crops additionally comprise lime—calcium oxide—that made the glass extra secure. Historic glassmakers additionally added supplies that impart colour to glass, reminiscent of cobalt for darkish blue or lead antimonate for yellow. The substances melded within the soften, contributing chemical clues that researchers search for right this moment.

“We will begin to parse the uncooked supplies that went into the manufacturing of the glass after which counsel the place on the earth it got here from,” says supplies scientist Marc Walton of Northwestern College in Evanston, Illinois, co-author of an article about supplies science and archaeological artifacts and art work within the 2021 Annual Evaluation of Supplies Analysis.

However these clues have taken researchers solely to date. When Shortland and colleagues have been investigating glass’s origins round 20 years in the past, glass from Egypt, the Close to East, and Greece seemed to be chemical lookalikes, tough to tell apart based mostly on the strategies accessible on the time.

The exception was blue glass, due to work by Polish-born chemist Alexander Kaczmarczyk who within the Eighties found that components reminiscent of aluminum, manganese, nickel, and zinc tag together with the cobalt that offers glass an abyssal blue hue. By analyzing the relative quantities of those, Kaczmarczyk’s staff even tracked the cobalt ore used for blue coloring to its mineral supply in particular Egyptian oases.

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