During the age of the Roman Empire the quality and colours of the fabrics indicated the social status of their owners. The more brilliant, vivid and striking the colours of the dyes, the more expensive, exclusive and precious they were. The history of fabric dyeing shows numerous edicts regulating their production, trade and use of dyes in textiles, often protected by secret information.
Coloured fabrics in precious dyes were diplomatic gifts, a sign of leadership and imperial monopoly. Dyeing manufacturers reproduced colours of the most precious gem stones with prolonged and expensive processes.

Purple was the most precious tinctorial material from which to obtain a range of vivid, deep and brilliant colours. It was necessary to have 12,000 murex or molluscs for 1.4 grams of pigment, scarcely enough for dying a single dress the size of the Roman toga. Also cochineal was greatly valued and expensive. It was necessary to have 60-80 female desiccated insects for 1 gram of pigment; but it needed a lot for dyeing a single dress.

In order to achieve the colour blue it was necessary to grow woad plants and form the leaves into special balls, called "blue gold". As it is known, the history of colour from the XVI^th century (isatis tinctoria) is interwoven with that of indigo (indigofera tinctoria). Unfortunately chemical analysis cannot detect whether blue dye is from woad or indigo, so it is not possible to know exactly the botanical species used in dying.

Purple, kermes and woad are the three colouring substances about which Dominique Cardon had organised the interesting exhibition "Mediterranean Precious Dyeing" supported by theMusée des Beaux Arts de Carcassonne (France) and Centro Documentació I Museu Textil de Terrassa (Spain).
The importance of chemical analysis of colouring substances of textiles was the main theme of this exhibition adopting the most advanced techniques of liquid chromatography (CLHP), in accordance with a system of experimental archaeology. So it was possible to identify each tint which results from the dyeing with each consecutive immersion of colour, also the proportion of the dyes and finally the mordanting and finishing processes. In fact next to the priceless textile showpieces, dyed in purple or kermes, there were also counterfeited colours, made by the cheaper materials such as madder and woad.

This interesting research about ancient colour dyes is interlaced with the history of chemistry and also alchemy, where the conception of transmutation was based on techniques borrowed from the natural processes. So in those days the counterfeits had a different value. It is known, for example, that the Medieval ages assigned great value to the rhinestone, almost as much as a gemstone, because it had an inner spark of light.
Among the various documents about dyeing recipes we admired a rare fragment of cuneiform Assyrian-Babylonian tablet from the 7^th Century BC In this text there was a recipe for imitation purple, with two immersions in succeeding baths of madder and indigo. Furthermore it is the oldest source of describing the range of blue colours in vat dyeing.
Likewise some priceless papers of Leyda Papyrus (Egypt II-I century BC) are fundamental on dyeing history, in addition to recipes for imitating gold, silver and precious stones, they indicate how to make a purple colour, with lists of materials and the processes of mordanting and finishing.

Among the most recent dyeing studies there was the medical material of Swedish naturalist Charles Linné (1707-1778) and French zoologist Henri de Lacaze-Duthiers (1821-1901) who did research on murex.
The most used purple gastropods in the ancient Mediteranean were murex brandaris, for dyeing a deep red, called argaman in the Bible; murex trunculus, for blue shades called tekhelet in the Bible, and haemastoma for violet tints. An example of their beautiful colours are in the Coptic textile showpieces, from the Palmyra oasis tombs (I-II century BC), made on Asiatic cashmere, Chinese silk, linen, cotton and gold thread.
Also cochineal insects, replacing purple since Medieval times, were from different species: kermes vermilio (porphyrophora), also called Polish or Armenian Cochineal; India Cochineal (kerria) and American Cochineal (dactylopius). As their colour was less violet than purple, it made scarlet tint with metallic salt mordanting and consecutive baths of dye with madder.
At the Terrassa Museum there were a lot of superb textiles dyed in Cochineal: a tunic fragment with two people on a red background from kermes or madder with alum (V^th century) from the Georges Labit Museum of Toulouse. The famous "Textile of Eagles" from Siguenza cathedral, made from kermes with tannin (XII^th century) and a velvet chasuble, from American cochineal, from the Cathar Church of Saint Andrea (XV^th century).
The value of kermes was not limited to dye making, it was used as a syrup like a medicine with unlimited virtues: the alkermes. This beverage was considered to be a panacea, capable of curing cardiac weaknesses, toning the spirit, stopping palpitations and fainting fits, reinforcing the brain, establishing forces and expelling melancholy. Finally it was regarded as an aphrodisiac. Not for nothing was the travel briefcase of Napoleon I's personal doctor stocked with kermes powder to cope with all pharmaceutical emergencies.

The history of blue dye was also well documented. It is known that until the importing of indigo (indigofera tinctoria) from America in the XVI^th century, blue dye was made in Europe from woad, the leaves being wrapped and fermented to make paste balls. Some recipes illustrate the mixing of woad with Asiatic indigo, since the XVII^th century. Numerous dye colours had woad in the first dye bath; black, scarlet, green; also dyers made samples of blue shades, from light to dark as examples of the colour bath base. Jean Astruc's treatise (Paris, 1737) is a unique account with illustrations of a wooden woad mill, it describes the ancient process of preparing coquaignes with fermented leaves of the plant for dyeing in the vat.

At the conclusion of the exhibition the Autumn/Winter 1999-2000 "Nature and Couture" Collection of Olivier Lapidius was shown, with superb textiles dyed in kermes paste, madder and other plants, testifying that today it is also possible to have very beautiful and special colours with natural dyes.