Tyrian purple

Tyrian purple is the dye extracted from the murex shellfish, first produced by the Phoenician city of Tyre in the Bronze Age and also known as royal or imperial purple. For many ages it was the most celebrated of all dye colours, and it may have been the first dye to be permanently fixed on wool or linen. Its standing rested on a colour that could be drawn from the sea snail and fixed in cloth, a combination that made it a byword for magnificence.

The dye known as Tyrian purple was produced primarily from three species of sea molluscs of the family Muricidae common in the Mediterranean Sea: Hexaplex trunculus, Bolinus brandaris and Stramonita haemastoma, also known as Murex trunculus, Murex brandaris and Thais haemastoma. The Muricidae are marine snails of rocky shallow waters, found worldwide and mainly in tropical seas, with elaborately spined or frilled shells.

The purple colour is not present in the living mollusc but is held as colour precursors, sometimes called chromogens or prochromogens, in the hypobranchial gland. A notable characteristic of many murex species is their ability to exude a yellow fluid that transforms into a purple dye when exposed to sunlight.

The major component of Tyrian purple is 6,6'-dibromoindigo. The colour components that confer purple and are present only in molluskan dyes are 6-monobromoindigotin, monobromoindirubin, 6,6-dibromoindigotin and 6,6-dibromoindirubin. The two principal markers of this dye are MBI and DBI.

Because the snails contain only minute amounts of dye, the purple has always been very costly. Caseau estimated that about 10,000 shellfish would produce 1 gram of dyestuff, enough only to dye the hem of a garment in a deep colour.

The ancient method began with the animal itself. Large murices had their glands removed with a metal tool, while smaller specimens were crushed whole; the glands were then heated in a vat of salt water for ten days until they melted, leaving behind a colourless compound that produced the purple dye when re-exposed to air and sunlight.

Pliny stresses that it was a great point to take the fish alive, since when it dies it spits out the juice; the juice was extracted from larger specimens after the shell was taken off, while small fish were crushed alive together with their shells. The vein taken from the fish was laid in salt at the rate of a sextarius, or pint and a half, of salt to every hundred pounds of the purple liquor. The prepared colour was then boiled in lead vessels, with one hundred pounds and a half of colour put into every amphora, a vessel holding about eight wine gallons.

The dye yielded a spectrum that ran from pale mauve to black-purple and from almost red to deep blue, with the final shade fixed during the dyeing process itself. The colour held fast and stayed bright after washing.

The highest grade of purple cloth was known as dibapha, meaning 'twice dipped'. Pliny records a price of a hundred deniers a pound for violet purple against a thousand deniers a pound for dibapha.

Pliny ranked the best purple by region: Tyre in Asia, Meninx and the parts of Gaetulia bordering on the Ocean in Africa, and Laconia in Europe.

The Latin name purpura derives from the shellfish called Purpura. The Greek name Phoinikes, meaning 'red', was applied to the Phoenicians, perhaps on account of the dye, and the Greeks called them the 'purple people' because the dye stained the skin of those who worked with it. Another name given to the inhabitants of Iron Age Syria was Kanaanites, which likewise means 'red'.

The Phoenicians were a seafaring trading people whose city-states rose to prominence after about 1200 BCE, with Tyre and Sidon emerging as the most powerful of these states while Byblos and Baalbek served as spiritual centres. Their colonies, planted on Cyprus, Sicily, Libya, Africa, the Maghreb, Andalusia and Morocco, together formed an interconnected trade network. Through this network the Phoenicians carried goods and manufactures across the Mediterranean world.

The Phoenicians became renowned as sellers of purple, and the manufacture of the dye was exported as far as Carthage. The Romans later adopted purple as a symbol of imperial authority.

The scale of production is preserved in the shell deposits themselves: the mound at Sidon stands 40 metres high, and vast deposits of shells have been excavated on the outskirts of both Sidon and Tyre. The species exploited for the dye was all but driven to extinction along the coasts of Phoenicia. Crushed shells have also been found at sites in Spain, Tunisia and Morocco.

By the end of the fifth century BCE Phoenician trade routes stretched from India to Mogador, the modern Essaouira.

The earliest evidence for purple dyeing is largely indirect. Heaps of murex shells have been dated to around the 19th century BCE. The shells recovered at Sarepta during the 1969-74 Pritchard excavations included three large accumulations of crushed Murex trunculus. Taken together the finds place the earliest purple production no earlier than about 1350 BCE and suggest that shell purple-dye was produced first in the Aegean and Italy before being introduced into the Near East.

Tel Shiqmona is the only site in the Near East or around the Mediterranean, and indeed in the entire world, where a sequence of purple-dye workshops has been excavated. It preserves clear evidence for large-scale sustained manufacture of purple dye and dyeing in a specialized facility for half a millennium during the Iron Age. The workshops operated for about half a millennium c. 1100-600 BCE under the Kingdom of Israel, supplying kingdoms across the region and probably used in the parochet of the Temple. HPLC showed all 28 artifacts stained with Muricidae dye, and chromatogram ratios of 20 samples indicated H.

Other Bronze and Iron Age sites in the southern Levant with purple-dye-related finds are Tel Kabri in the Akko Plain, nearby Tell Keisan, Tel Akko and Tel Dor, each yielding only a few stained sherds or vessels.

The Timna Valley has yielded a 3000-year-old wool textile with shellfish-based dye from Slaves' Hill (Site 34). The textile was radiocarbon-dated to the late 11th to early 10th centuries BCE and is the first such find in the Southern Levant.

The Hebrew Bible terms argaman and tekhelet parallel the Akkadian argamannu and takiltu, and most scholars link tekhelet to Hexaplex trunculus. The dark blue tekhelet was also a form of Tyrian purple.

There was no global restriction on who could wear it only local restrictions on some festival days when it was reserved to the top ranks. Later laws decreed who could and could not wear purple.

The Edict on Maximum Prices issued in 301 set prices ranging from one denarius for fresh green animal fodder up to 150000 denarii for a male lion or for purple-dyed silk. Purple-dyed wool stood at 50000 denarii and lighter purple wool at 32000. Unregulated goods were priced by quality of purple linen weight and workmanship.

In the same edict one pound of purple dye was valued at around three pounds of gold.

The imperial dyeworks were transferred to Constantinople when the legendary city of Tyre was taken over by the Arabs, and the Fourth Crusade between 1202 and 1204 left the city wrecked. Tyre had continued to produce its famous purple dye and prospered as an important Christian centre, but after the city was taken by the Muslim Mamluk Sultanate the production of purple dye and garments ended as cheaper dyes were now available.

The scarcity of murex provoked the disappearance of the techniques for manufacturing the purple dye, yet the colour remains a sign of magnificence, and the cardinals of the Roman Catholic Church keep the privilege of wearing purple.

Systematic inquiry into the purple-producing molluscs began with William Cole of Bristol in 1685, whose observations extended to an Irish industry devoted to marking shellfish. Cole located Purpura capillus, known as Nucella lapillus, at Minehead. He concluded that sunlight both develops the colour and generates the accompanying stench. His plan to carry live molluscs to London for the King was never realized.

Linnaeus in the eighteenth century drew up a species list naming murex brandaris and murex trunculus. In the mid-nineteenth century Henri de Lacaze-Duthiers studied the three Mediterranean species Murex trunculus, Murex brandaris and Purpura haemastoma together with Nucella lapillus. He demonstrated the potential of these molluscs for a photographic printing process.

Paul Friedländer first identified the structure of the dye as 6,6'-dibromoindigo in 1909. He showed that the product contained bromine. His analysis required 12,000 Murex brandaris snails to yield 1.4 g of pure pigment.

The first synthesis of 6,6'-dibromoindigo was achieved by Sachs and Kempf in 1903 through a Claisen condensation of 4-bromo-2-nitrobenzaldehyde with acetone. The Friedländer method suffered from the drawback of expensive bromoanthranilic acid. Later synthetic efforts were judged on convenience, cost, safety and yield.

The first synthetic rival to the ancient dye was mauve, or aniline purple, synthesized by William Henry Perkin in 1856 from chemicals derived from coal tar. It became the first commercialized synthetic dyestuff and formed the basis of a new chemical and eventually pharmaceutical industry. Murex purple was superseded by synthetic dyes in the nineteenth century, though its fastness took years to replicate.