The secret of transparent glass: scientists traced its history from ancient Rome to Egypt

The secret of transparent glass

37 fragments of ancient glass discovered during archaeological excavations in the city of Geras, in Jordan, were subjected to a rigorous laboratory research. The scientists were able to measure the isotopes of hafnium in the debris and correlate them with the composition of the sand along the Nile River in Egypt. The research is carried out by a group of specialists from Aarhus University in Denmark that is trying to learn the secret of "Alexandrian" glass.

It was one of the most valuable materials that were popular during the Roman period in Egypt. In an attempt to unravel the mystery of transparent glass, the researchers turned to the amount of the rare element hafnium.

The glass industry in ancient Rome was widely known for its unique production. A huge number of glass products were produced here, ranging from vessels of different sizes to mosaics. Most of the products were manufactured in Egypt and the Levant region of the Middle East.

At certain period of time, the demand for a colorless, transparent version of the sekl began to grow, and later it was called "Alexandrian glass". For many years, scientists around the world have built their assumptions about the origin of that transparent material.

The scientists from Aarhus University were the first to develop a method to distinguish between clear glass made in Egypt and the Levant during the Roman Empire. The sand of the Nile had lime in its composition. It helped to preserve the glass and make it more durable. In Rome, glassmakers added antimony to it, and thus the glass became like a crystal, it became transparent for the first time.

A researcher Gri Hoffmann Barfod noted that the first mention of this dates back to the beginning of the fourth century AD. Even then, the Roman emperor Diocletian mentioned the transparent "Alexandrian glass".

It was twice expensive as the usual one, which in the Levant was treated with manganese. The scientists dreamed to solve that riddle. After all, manganese is used in glass production today. However, manufacturers have failed to obtain Alexandrian glass.