medieval purple dyes

[Dept of PMM Artists & things]

Definition:

Royal Purple (also called Tyrian Purple or Byzantine Purple) is the deep purple pigment used for elite clothing beginning in the Roman period and illuminated manuscripts through the Middle Ages. The dye comes from several species of the carnivorous marine mollusc, the whelk (including but not limited to Murex spp, Nucella spp and Purpura spp).

Whelks which produce purple dyes are found world-wide, including the Americas, but Royal Purple was most famously first produced in or near the city of Tyre in Lebanon, during the Imperial Roman period.

The purple-bearing part of the whelk is the hypobranchial gland, which produces a colorless or yellow mucus. When exposed to sunlight and air the mucus changes color several times, but at last becomes a stable, non-water-soluble purple pigment somewhere between blue-violet and red-purple. While the pigment itself is created without additional manipulation, to make the quantities of dye required for the elite purple purposes, a vat-dying process was invented.

History and Royal Purple

According to historical documents (specifically, Book 8 of Pliny the Elder’s Historia naturalis), processing of whelk mucus involved adding honey or salt, water, and long-term heat processing in a lead vessel.

Archaeological sites with evidence for whelk dying include a 7th century AD dye workshop on the island of Inishkea North in County Mayo, Ireland, excavated in the 1950s by Françoise Henry. Inishkea North was home to an early Christian monastery, where the monks were known to have produced whelk dyes.

Sources

Carole Biggam's article listed below is a comprehensive history of whelk dying, including linguistic and historical data.

Biggam, C. P. 2006 Knowledge of whelk dyes and pigments in Anglo-Saxon England. Anglo-Saxon England 3523-55.

This glossary entry is part of the Dictionary of Archaeology. Any mistakes are the responsibility of Kris Hirst.

Also Known As: Tyrian purple, Imperial purple, Byzantine purple

[Dept of PMM Artists & things]

Chinese or Han Purple was a manufactured pigment used between about 1200 BC and 220 AD, most famously on the terracotta soldiers of the Qin emperor.

Han purple is a compound based on copper silicate, and the purple color derives from the red impurity of copper oxide. Like the other blue pigments developed by the Chinese (the others are Han Blue and Ultramarine), Han Purple has been found in objects in the Western Zhou dynasty (1207-771 BC), the Eastern Zhou period (770-221 BC) and the Qin and Han dynasties (220-207 BC and 206 BC-220 AD). Han Purple has been identified on the terracotta army; but not Han blue (the blue used was azurite).

Using historical records, a research team led by Zhi Liu has argued that the color was invented by Taoist alchemists to imitate jade, an important substance for the Taoist religion. Cullen, however, believes that the historical reference to the Tao (or Dao) is not necessarily a reference to the Taoist religion, but is currently understood to refer to a wide range of secular knowledge and philosophy. Liu points out that the use of jade in burials was banned at the end of the Han Dynasty by the Emperor Wen, along with other conspicuous consumption traits of the Han and Qin dynasties, as epitomized by the Emperor Qin's tomb.

The recipe for Chinese purple was lost, but recovered when modern day alchemists armed with high-resolution transmission electron microscopy, electron energy loss spectroscopy, and x-ray microanalysis, were able to reconstruct the pigment.

Sources

Stanford's exhibit on Chinese Purple is an excellent source for more information on the Liu research.

Berke, Heinz 2007 The invention of blue and purple pigments in ancient times. Chemical Society Reviews 36:15–30.

Cullen, Christopher in press Taoism (Daoism) and 'Chinese Purple': a note on some historical iss... Journal of Archaeological Science in press.

Liu, Zhi in press Reply to "Taoism (Daoism) and ‘Chinese Purple’: a note on some hist... Journal of Archaeological Science in press.

Liu, Z., et al. 2007 Influence of Taoism on the invention of the purple pigment used on .... Journal of Archaeological Science 34(11):1878-1883.

This glossary entry is part of the Dictionary of Archaeology. Any mistakes are the responsibility of Kris Hirst.

[Dept of PMM Artists & things]

Tyrian purple (Greek, πορφύρα, porphyra, Latin: purpura), also known as royal purple, imperial purple or imperial dye, is a purple-red natural dye, which is extracted from sea snails, and which was possibly first produced by the ancient Phoenicians. This dye was greatly prized in antiquity because it did not fade but became more intense with weathering and sunlight.

Tyrian purple was expensive: the 4th-century-BC historian Theopompus reported, "Purple for dyes fetched its weight in silver at Colophon" in Asia Minor. The expense meant that purple-dyed textiles became status symbols, and early sumptuary laws restricted their uses. The production of Tyrian purple was tightly controlled in Byzantium and was subsidized by the imperial court, which restricted its use for the colouring of imperial silks, so that a child born to a reigning emperor was porphyrogenitos, "born in the purple", although this term may also refer to the fact that the imperial birthing apartment was walled in the purple-red rock known as porphyry.

The dye substance comprises a mucous secretion from the hypobranchial gland of one of several medium-sized predatory sea snails that are found in the eastern Mediterranean. These are the marine gastropods Bolinus brandaris the spiny dyemurex, (originally known as Murex brandaris (Linnaeus, 1758)), the banded dye-murex Hexaplex trunculus, and the rock-shell Stramonita haemastoma. The dye is an organic compound of bromine (i.e. an organobromine compound), a class of compounds often found in algae and some other sea life, but much more rarely in the biology of land animals.

In Biblical Hebrew, the dye extracted from the Bolinus brandaris is known as argaman (ארגמן). Another dye extracted from a related sea snail, Hexaplex trunculus, produced an indigo colour called tekhelet (תְּכֵלֶת‎), used in garments worn for ritual purposes.

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.) The dog whelk Nucella lapillus, from the North Atlantic, can also be used to produce red-purple and violet dyes.

In nature the snails use the secretion as part of their predatory behaviour and as an antimicrobial lining on egg masses. 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 that "twelve thousand snails of Murex brandaris yield no more than 1.4 g of pure dye, enough to colour only the trim of a single garment."

Recent research in Organic electronics has shown that Tyrian Purple is an ambipolar organic semiconductor. Transistors and circuits based on this material can be produced from sublimed thin-films of the dye. The good semiconducting properties of the dye originate from strong intermolecular hydrogen bonding that reinforces Pi stacking necessary for transport.