Purple became the colour of emperors because it came from rotting sea snails.
Tyrian purple was squeezed from the glands of predatory sea snails. One estimate puts it at about 12,000 snails for just 1.4 grams of dye, enough to trim a single garment. The dye works stank of rotting fish. By the fourth century, only the Roman emperor could wear it.
The dye takes its name from Tyre, a Phoenician city in what is now Lebanon. The Phoenicians were producing it by around 1200 BC, possibly earlier, and some have suggested the name Phoenicia itself means 'land of purple'. Piles of crushed murex shells on Crete hint that the Minoans may have been making it centuries before that. Its chemistry is a bromine-containing cousin of indigo, a class of compound much more common in sea life than on land.
Making it was brutal work. The snails secrete the substance from a gland to subdue prey and protect their eggs. Dyers either milked them or crushed them in vast numbers, then left them to steep and boil for days. Ancient writers complained of the stench; one Egyptian papyrus says a dyer's hands reek like rotting fish, and the Talmud allowed a woman to divorce a husband who became a dyer after their marriage.
Its prize quality was that it did not fade. It was said to grow brighter with sun and weathering, and the most admired shade was the colour of clotted blood, almost black. The historian Theopompus reported that it sold for its weight in silver. Rome regulated who could wear it: senior magistrates had a purple stripe on their togas, triumphant generals wore it whole, and by the fourth century AD it was reserved for the emperor alone. To 'don the purple' meant to take the throne, and Byzantine royal children were 'born in the purple'.
The Byzantine industry collapsed after the sack of Constantinople in 1204, and western Europe turned to red kermes, made from insects, for its luxury colour. In 2021 archaeologists in Israel's Timna Valley found wool fibres dyed with royal purple from around 1000 BC, the first direct evidence of such fabric from antiquity.
Source: Wikipedia — Tyrian purple · Text summarised from Wikipedia (CC BY-SA 4.0)
