Discovery of a Bronze Age dye workshop reveals secrets of history’s most precious pigment

By Taylor Nicioli, CNN

(CNN) — For thousands of years, one color rose above all others — and was worth more than its weight in gold, according to a fourth-century imperial edict.

Tyrian purple was a highly prized pigment developed in the Bronze Age, and it retained its status into the late medieval period. The ancient Greeks and then the Romans revered the royal color, produced from Mediterranean sea snails, for its resistance to the inevitable fading of plant-based dyes used at the time. But with the eventual fall of the Byzantine Empire, the recipe was lost.

During an excavation of two early Mycenaean buildings discovered on the Greek island of Aegina, archaeologists unearthed several pottery fragments with residue of 3,600-year-old Tyrian purple dye, according to a study published June 12 in the journal PLOS One.

The pigment is so well preserved that it could still be used to dye textiles today, said lead study author Dr. Lydia Berger, a senior scientist in the department of classics at the Paris Lodron University of Salzburg in Austria. The researchers also found crushed mollusk shells and various stone tools, believed to be used in the dye-making process.

The pigment, alongside the other remnants of an early functioning purple dye workshop uncovered at the ancient site, known as Kolonna, has shed some light on the mysteries still surrounding the once highly sought-after color.

A laborious process for an elite color

The earliest record of Tyrian purple production dates to the Middle Bronze Age (2000 BC to 1600 BC), the study authors wrote. Historians believe people within the ancient city of Tyre, on the coast of what is now Lebanon, first created the dye, which is sometimes referred to as Mycenaean purple. The ancient Greeks called this region Phoenicia, or “land of purple,” according to the University of Michigan.

A combination of secrecy around the process and a lack of early archaeological evidence from the Greek Bronze Age civilizations near the Aegean Sea likely led to the recipe being lost. It took hundreds of years of research plus modern experimentation to get close to the presumed procedure.

“It was a process that was made by trial and error, and these people really knew the secret. Now we have lost all the secrets,” said Maria Melo, an associate professor in the department of conservation and restoration at Nova University of Lisbon, Portugal, who was not involved with the discovery. “Most likely, we will not be able to reproduce their process, but we can try to do something similar.”

Creating the historic hue required an immense number of sea snails found along the coast of the Mediterranean Sea, as documented by ancient Roman authors. Dye artisans commonly sought the species known today as the banded dye-murex — the species preferred by those on the island of Aegina, the chemical analysis of the found pigment showed — as well as the spiny dye-murex and the red-mouthed rock shell, according to the study.

Tyrian purple is often described as being a deep reddish purple in ancient Roman times, but depending on the snail used and the amount of heat exposure, the shade could range from a dark indigo to a lilac or deep red, Melo said.

Once collected, the snails had to be kept alive until the purple dye makers were ready to crush them and extract the mollusk’s mucus glands. The snail remains would then be left to seep with a regulated exposure to heat for several days, as the color would turn from yellow to green and then to purple and sometimes dark red, Berger said.

The process came with a fishy odor, one that the researchers recognized when they came across the purple pigment residue in the recent excavation at Kolonna, she added.

One estimate said it could take upward of 12,000 snails to get 1 gram of dye. But modern experiments have shown that fewer snails can yield the same amount of dye, depending on how light or dark one wants the pigment to be, said Rena Veropoulidou, an archaeologist with the Hellenic Ministry of Culture in Greece, who was not involved with the new study. For example, Veropoulidou used 800 snails in a 2008 experiment to dye five pieces of textile measuring 20 by 20 centimeters (8 by 8 inches), she said.

Who wore purple?

Those who would have worn purple during the Bronze Age remain a mystery, but it is often assumed that the color was only worn by people of prominence due to the dye’s intricate process, Veropoulidou said.

During this time, there is only evidence of Tyrian purple being used for textiles and wall paintings. However, there is more knowledge surrounding the dye’s purpose in ancient Rome, where the color was reserved for the elite and royalty only, Veropoulidou explained. There are depictions of Julius Caesar wearing deep purple togas, and during the Byzantine Empire, AD 330 to 1453, the emperor alone had the right to don the color.

The newly discovered workshop appears to be on the smaller side, so it’s possible the dye was a private stash used by those living on the island, rather than sent out for trade, Berger added, which could indicate that the color was for more common use.

“I think the first thing that attracted people’s attention, first of all, is the color is extremely deep — it was a very vivid, attractive color — but also the color could be kept alive and nice for a long period of time, maybe for two, three, four centuries, which is something amazing if you consider that the way we wash our clothes now, they fade after two or three times that we wash them,” Veropoulidou said.

More mysteries behind the hue

During the excavation, the researchers also uncovered 2,592 mammal remains, including the bones of young pigs and lambs.

While the study authors note they are not sure of the remains’ connection to the dye-making process, Berger said it could be evidence of religious sacrifices that were made to protect the site, due to the importance of the color.

Another theory is that the bones were used in some way to help regulate the temperature needed to get the perfect shade of purple, Melo said. “It’s amazing the knowledge of these guys, because even for us, it’s difficult to control temperature (when creating natural dyes). They were able to control the temperature at a certain degree — were these bones there to help control the temperature? We don’t know.”

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