After it is taken, the vein 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. “The most favourable season for taking these fish is after the rising of the Dog-star (= Sirius), 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. The best known historical description of the dyeing procedure can be found in Pliny’s the Elder “Natural history” (1): It has been used almost exclusively for dyeing textiles and not as a pigment for painting. The structure is similar to indigo with the sole difference of the two bromine atoms attached to the six-membered rings. It is the bromoindigos which are exclusively the signature components, there being no other source.” Shellfish purple is composed of a mixture of indigo dyes: indigo, monobromoindigo and dibromoindigo with smaller amounts of the corresponding indirubins. The name is derived from the city of Tyre, now in Lebanon, but since the distribution of purple producing snails is world-wide, a more appropriate descriptor would be shellfish purple. Currently, the Muricidae are divided into three subfamilies: Muricidae (the murexes), Ocenebrinae (the predatory sea snails, Nucella and Ocenebra) and Rapaninae (rockshells) and they are to be found across the globe from Central America to Japan, but famously and best known in the Mediterranean.

Tyrian purple comes from marine molluscs of the Muricidae family and the colour precursors are contained in the hypobranchial gland. It is the oldest, most well-known, most expensive, most prestigious and most vivid dye or pigment. “The topic of Tyrian purple abounds with superlatives. This pigment is one of the oldest and also most valued and most expensive natural colorants. Chris Cooksey writes in his review article (1):

Tyrian 2000 art