clad in Tyrian purple, 6th-century mosaic at
Basilica of San Vitale,
Ravenna,
Italy The
colour-fast (non-fading) dye was an item of luxury trade, prized by
Romans, who used it to colour
ceremonial robes. Used as a dye, the colour shifts from blue (peak absorption at 590 nm, which is yellow-orange) to reddish-purple (peak absorption at 520 nm, which is green). It is believed that the intensity of the purple hue improved rather than faded as the dyed cloth aged.
Vitruvius mentions the production of Tyrian purple from shellfish. In his
History of Animals,
Aristotle described the shellfish from which Tyrian purple was obtained and the process of extracting the tissue that produced the dye.
Pliny the Elder described the production of Tyrian purple in his
Natural History: The most favourable season for taking these [shellfish] is after the rising of the
Dog-star, or else before spring; for when they have once discharged their waxy secretion, their juices have no consistency: this, however, is a fact unknown in the dyers' workshops, although it is a point of primary importance. After it is taken, the vein [i.e. hypobranchial gland] is extracted, which we have previously spoken of, to which it is requisite to add salt, a sextarius [about ] to every hundred pounds of juice. It is sufficient to leave them to steep for a period of three days, and no more, for the fresher they are, the greater virtue there is in the liquor. It is then set to boil in vessels of tin [or lead], and every hundred amphorae ought to be boiled down to five hundred pounds of dye, by the application of a moderate heat; for which purpose the vessel is placed at the end of a long funnel, which communicates with the furnace; while thus boiling, the liquor is skimmed from time to time, and with it the flesh, which necessarily adheres to the veins. About the tenth day, generally, the whole contents of the cauldron are in a liquefied state, upon which a fleece, from which the grease has been cleansed, is plunged into it by way of making trial; but until such time as the colour is found to satisfy the wishes of those preparing it, the liquor is still kept on the boil. The tint that inclines to red is looked upon as inferior to that which is of a blackish hue. The wool is left to lie in soak for five hours, and then, after
carding it, it is thrown in again, until it has fully imbibed the colour. Archaeological data from
Tyre indicate that the snails were collected in large vats and left to decompose. This produced a hideous stench that was mentioned by ancient authors. Not much is known about the subsequent steps, and the actual ancient method for mass-producing the two murex dyes has not yet been successfully reconstructed; this special "blackish clotted blood" colour, which was prized above all others, is believed to be achieved by double-dipping the cloth, once in the indigo dye of
H. trunculus and once in the purple-red dye of
B. brandaris. This story was depicted by
Peter Paul Rubens in his painting ''
Hercules' Dog Discovers Purple Dye''. According to
John Malalas, the incident happened during the reign of the legendary
King Phoenix of Tyre, the eponymous progenitor of the Phoenicians, and therefore he was the first ruler to wear Tyrian purple and legislate on its use. Recently, the archaeological discovery of substantial numbers of Murex shells on
Crete suggests that the
Minoans may have pioneered the extraction of Imperial purple centuries before the Tyrians. Dating from collocated pottery suggests the dye may have been produced during the Middle Minoan period in the 20th–18th century BC. Accumulations of crushed murex shells from a hut at the site of
Coppa Nevigata in southern Italy may indicate production of purple dye there from at least the 18th century BC. Additional archaeological evidence can be found from samples originating from excavations at the extensive Iron Age copper smelting site of "Slaves' Hill" (Site 34), which is tightly dated by radiocarbon to the late 11th–early 10th centuries BC. By contrast, Jacoby finds that there are no mentions of purple fishing or dyeing, nor trade in the colorant in any Western source, even in the Frankish Levant. The European West turned instead to
kermes dye provided by the insect
Kermes vermilio, known as
grana, or
crimson. In 1909, Harvard anthropologist
Zelia Nuttall compiled an intensive comparative study on the historical production of the purple dye produced from the carnivorous
murex snail, source of the royal purple dye valued higher than gold in the ancient Near East and ancient Mexico. Not only did the people of ancient Mexico use the same methods of production as the Phoenicians, they also valued murex-dyed cloth above all others, as it appeared in codices as the attire of nobility. "Nuttall noted that the Mexican murex-dyed cloth bore a "disagreeable ... strong fishy smell, which appears to be as lasting as the colour itself." Likewise, the ancient Egyptian
Papyrus of Anastasi laments: "The hands of the dyer reek like rotting fish". So pervasive was this stench that the
Talmud specifically granted women the right to divorce any husband who became a dyer after marriage. In 2021, archaeologists found surviving wool fibers dyed with royal purple in the
Timna Valley in Israel. The find, which was dated to , constituted the first direct evidence of fabric dyed with the pigment from antiquity. ==Murex purple production in North Africa==