German scholar reviews glassmaking techniques across history

AMMAN — In order to work interdisciplinary, the archaeologist has to combine cuneiform texts, archaeometrical data (interpretation of chemical data) and information gained from experimental studies, according to a German scholar.

During her recent lecture, “Glass and Glassmaking in the Iron Age Period” held at German Protestant Institute for Archaeology (GPIA) on April 5^th, Katharina Schmidt, director of GPIA, emphasised the importance of the manufacturing techniques applied in glassmaking in ancient times.

“Certainly, glass and glass objects on a larger scale regularly appear in the late 16^th century BC in Mesopotamia,” she said, adding that “glass objects disappeared almost entirely from Mesopotamia and Egypt towards the end of the late 13^th century BC, in a wake of political upheavals in the region”.

The major period covered during the presentation extends between 1000 BC and the 6th century BC. Also known in historiography as “The Iron Age Period”, this era includes the rise and fall the Neo-Assyrian Empire, which reached its maximum expansion in the 7^thcentury BC, Schmidt explained.

Various manufacturing techniques were applied to the glass object, including mosaic technique, core-forming and “cast and cut”, the expert, who received her PhD in Ancient Near Eastern Archaeology at the Ludwig-Maximilians University in Munich, said.

The Amman Bowl is a very particular piece that was found on the Amman Citadel during the first destruction phase of the Ammonite palace on the lower slopes, Schmidt highlighted, adding that “this fragment of a bowl is a unique fragment”.

“The bowl itself is made of copper, with recessed bands inlaid with different glass. Similar glass inlays were also found in Nimrud, Arslan Tash and Samaria,” the expert outlined.

Moreover, three chemical processes have been observed during this period, marking a significant innovation with regard to the history of glass technology.

First, transparent glass is used for the first time, as a result of an intentional use of a chemical component, the antimonate, which functioned as a decolouriser. 

“At the current state of research, it looks like that transparent glass was produced deliberately during the period of the Neo-Assyrian Empire,” Schmidt said.

She observed that the largest number of transparent glass objects was generally found at Nimrud. 

“This chemical innovation of colourless glass occurs solely in connection with objects made using the ‘cast and cut’ technique, which was a ‘novelty’ in the early first millennium,” Schmidt emphasised.

“Therefore, it was very likely that both “innovations” were closely interlinked with each other”, she pointed out.

“As the second chemical novelty, the so -called ‘high-lead high-copper’ glass appears,” the scholar said, claiming that this was “a red-coloured glass that appeared for the first time in history.”

High-lead high–copper glasses were generally less likely to devitrify, Schmidt noted, adding that it resulted in a more brilliant “gem-like” shiny colour.

The third novelty had to do with the use of different kinds of fluxes: “We have plant ash as well as mineral natron that served as fluxes in order to lower the melting point of quarz.”

“Whereas plan ash was already used in the Late Bronze Age, the mineral natron only started being used in the early first millennium,” she explained.

In addition to the manufacturing techniques, “cast and cut” glass became predominant in the early first millennium BC, she continued, stressing that it could be identified as a new technological development. 

The primary production of glass can be understood from the glassmaking texts, which can be identified as realistic recipes, the scholar underlined, adding that glass objects were differently valued. 

“It seems that core-formed objects were accessible to a wider range of people in the early first millennium,” the director said.

On the other hand, cast and cut glass was reserved for the palace: “It is very likely that the increased appearance of cast and cut glass was driven by the Neo-Assyrian Empire and was seen as a luxury product reserved for the king and his royal household.”

“For my future work, I hope to be able to extend my research on glass and probably other ancient materials from Jordan,” Schmidt said.