Tyrian purple

Murex brandaris, also known as the Spiny dye-murex

The chemical structure of 6,6′-dibromoindigo, the main component of Tyrian Purple

A space-filling model of 6,6′-dibromoindigo, based on the crystal structure

The Tyrian purple (in Greek, πορφύρα, porphyra, Latin: purpura), also known as royal purple, imperial purple or imperial dye, is a purple-red dye which was first produced by the ancient Phoenicians.

Tyrian purple was expensive: the 4th-century-BC historian Theopompus reported, "Purple for dyes fetched its weight in silver at Colophon" in Asia Minor.^[1] The expense rendered purple-dyed textiles status symbols, and early sumptuary laws dictated and forbade their use. The production of shellfish purple was tightly controlled in Byzantium and subsidized by the imperial court, which restricted its use for the coloring of silks for imperial use,^[2] so that a particularly elite member of the imperial family was porphyrogenitos, "born in the purple".

Collection

The dye substance occurs naturally, but must be harvested by humans. It consists of a fresh mucous secretion from the hypobranchial gland of a medium-sized predatory sea snail, the marine gastropod Murex brandaris, currently known as Haustellum brandaris (Linnaeus, 1758). This species is commonly called the spiny dye-murex, and it is a species in the family Muricidae, the murex or rock shells. The current range for this species is the "central and western Mediterranean".^[3]

In Biblical Hebrew, which like Phoenician is a dialect of Canaanite, the Tyrian purple-red dye extracted from the Murex brandaris is known as argaman ארגמן. Another dye extracted from a related sea snail, Hexaplex trunculus, produced a sky-blue indigo colour, called tekhelet^[4] תְּכֵלֶת‎ [təxelɛθ] (translated 'indigo') when processed in sunlight (see Photochemistry).

Many other species worldwide within the family Muricidae, for example Plicopurpura pansa (Gould, 1853), from the tropical eastern Pacific, and Plicopurpura patula (Linnaeus, 1758) from the Caribbean zone of the western Atlantic, can also produce a similar substance (which turns into an enduring purple dye when exposed to sunlight) and this ability has sometimes also been historically exploited by local inhabitants in the areas where these snails occur. (Some other predatory gastropods, such as some wentletraps in the family Epitoniidae, seem to also produce a similar substance, although this has not been studied or exploited commercially.)

In nature the snails use the secretion as part of their predatory behaviour and as an antimicrobial lining on egg masses.^[5][6] The snail also secretes this substance when it is poked or physically attacked by humans. Therefore the dye can be collected either by "milking" the snails, which is more labour intensive but is a renewable resource, or by collecting and then crushing the snails completely, which is destructive. David Jacoby remarks^[7] that "twelve thousand snails of Murex brandaris yield no more than 1.4 g of pure dye, enough to color only the trim of a single garment."

Royal blue

As well as Tyrian purple, the Phoenicians also made a purple-blue indigo dye, referred to as royal blue or hyacinth purple, which was made from a closely-related species of marine snail.

The Phoenicians established an ancillary production facility on the Iles Purpuraires at Mogador, in Morocco.^[8] The gastropod harvested at this western Moroccan dye production facility was Hexaplex trunculus (mentioned above) also known by the older name Murex trunculus (Linnaeus, 1758)).

This second species of dye murex currently occurs on "the Mediterranean and Atlantic coasts of Europe and Africa (Spain and Portugal, Morocco, and the Canary Islands)".^[9]

Historical overview of Tyrian purple

Byzantine Emperor Justinian clad in Tyrian purple, 6th-century mosaic at Basilica of San Vitale, Ravenna, Italy

The fast, non-fading dye was an item of luxury trade, prized by Romans, who used it to colour ceremonial robes. It is believed that the intensity of the purple hue improved, rather than faded, as the dyed cloth aged. Pliny the Elder described the dyeing process of two purples in his Natural History^[10]:

Archaeological data from Tyre indicate that the snails were collected in large vats and left to decompose. This produced a hideous stench that was actually 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 M. brandaris.^{[citation needed]}

The Roman mythographer Julius Pollux, writing in the second century BC, asserted (Onomasticon I, 45–49) that the purple dye was first discovered by Heracles, or rather, by his dog, whose mouth was stained purple from chewing on snails along the coast of the Levant. 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.^[11]

The production of Murex purple for the Byzantine court came to an abrupt end with the sack of Constantinople in 1204, the critical episode of the Fourth Crusade. David Jacoby concludes that "no Byzantine emperor nor any Latin ruler in former Byzantine territories could muster the financial resources required for the pursuit of murex purple production. On the other hand, murex fishing and dyeing with genuine purple are attested for Egypt in the tenth to thirteenth centuries."^[12] 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 vermilion provided by the insect Kermes vermilio, known as grana, or crimson, known as cochineal.

Dye chemistry

The main chemical constituent of the Tyrian dye was discovered by Paul Friedländer in 1909 to be 6,6′-dibromoindigo, a substance that had previously been synthesized in 1903.^[13] However, it has never been synthesized commercially.^[14][15]

In 1998, through a lengthy trial and error process, an English engineer named John Edmonds succeeded in cracking the secret of how to dye Tyrian purple. He researched recipes and observations of dyers from the 15th century through the 18th century. He explored the biotechnology process behind woad fermentation. After collaborating with an Israeli chemist, Edmonds hypothesized that an alkaline fermenting vat was necessary. He studied an incomplete ancient recipe for Tyrian purple recorded by Pliny the Elder. By altering the percentage of sea salt in the dye vat, he was able to successfully dye wool a deep purple colour. ^[16]

Modern hue rendition

Tyrian purple

Tyrian Purple
— Colour coordinates —
Hex triplet		#66023C
RGBB	(r, g, b)	(102, 2, 60)
HSV	(h, s, v)	(324°, 98%, 40%)
Source		Internet
B: Normalized to [0–255] (byte)

The true colour of Tyrian purple, like most high chroma pigments, cannot be accurately displayed on a computer display, nor are ancient reports entirely consistent, but these swatches give an indication of the likely range in which it appeared:

_________
_________

This is the sRGB colour #990024, intended for viewing on an output device with a gamma of 2.2. It is a representation of RHS colour code 66A ^[17], which has been equated to "Tyrian red" ^[18], a term which is often used as a synonym for Tyrian purple.

Shades of Tyrian purple colour comparison chart

Modern research shows, as discussed above, that various formulations of Tyrian purple existed on a continuous spectrum within approximately the following range of colours:

• Bright Tyrian Purple (Bright Imperial Purple) (Tyrian Pink) (Hex: #B80049) (RGB: 184, 0, 73)
• Medium Tyrian Purple (Medium Imperial Purple) (Tyrian Red) (Hex: #990024) (RGB: 153, 0, 36)
• Tyrian Purple (Imperial Purple) (Hex: #66023C) (RGB: 102, 2, 60)

References

6,6'-dibromoindigo, the major component of tyrian

See also

• Hexaplex trunculus
• Indigo dye
• Murex
• Purple

External links

• [5]

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