Other fields were to be explored to understand more of the practical use of murex snails and the problems. There was still the strive for the dry pigment.
The mucus-like secretion, once exposed by breaking the shell, is not at all fluid. There are no drops dripping from the gland which then can be dried and pulverized. Thus this did not advance the question of the dry pigment, but it lead to another discovery.
The glands were cut out and laid on rough salt. Within half an hour, they had humidified and coloured all of the salt. The wet mass was dried with a fan or over moderate heat stirring off and on to avoid sticking to each other or the bottom of the container.
These dried salt-glands do not provide a paint pigment, but they have proved very useful and efficient to set up a purple fermentation vat for dyeing. This could explain why dye-factories inland, far from the coast, are possible. Wolfgang Born comments on such factories, but did not mention the procedure discovered for transporting the dye-stuffs: “In the 6th century a process was discovered, which made it possible to preserve the shell-fish months after killing them. This discovery made it practicable to transport the animals to places far from the coast, and there to extract the dye. This may explain the report, according to which in the 7th century there was a private dye-works at This in Upper Egypt.”(Born 1937). Salted glands could be transported with great facility, well stored under dry conditions and used when needed. Recent experiments in the author’s atelier in collaboration with Christine Macheboeuf have proved that glands preserved in honey – an idea already expressed by Vitruvius in his treatise ‘On Architecture’ (VII, 13, 3) - for more than six months were still capable of producing a correct dye-bath.
These experiences did not create special art work, but helped to understand the difficulties of the ‘purpurarii’, the manufacturers of purple products, and naturally led to further explorations on related subjects such as purple parchment.
Parchment had replaced papyrus in the 4th century A.D. as the main support material for manuscript writing and illumination. It was used for royal documents and scribes in monasteries copied the Bible on to it. Parchment was prepared with great care and often the most precious colours were used to dye or decorate them. Purple-coloured parchment with writing executed in silver or gold can be seen on the most prestigious documents. (Wattenbach 1896).
Was the purple of these manuscripts of animal origin? Were they dyed or painted with purple and how was this done?
The technique of applying real purple seems to have been lost since the manufacturing of this colour came to an end after the fall of Byzantium in 1453. According to modern science, the so-called purple manuscripts even from earlier periods were often falsified with other, cheaper red and violet dye-stuffs or pigments. A German scholar, Heinz Roosen-Runge, carried out various experiments to colour parchment with shellfish purple in order to identify real purple in old manuscripts. He was left with doubts on his techniques and came to the conclusion that very few samples exist which can be called purple parchment. (Roosen-Runge 1967).
After weeks of trial and error, the author was finally successful in colouring parchment using shellfish purple. Different methods were invented, but basically the glands were cut out, collected in a dark bottle to which water was added and a piece of previously prepared parchment submerged. More glands could be added to intensify the result. In some experiments a small quantity of honey was added and the bottle exposed to sunshine, which gave sometimes a rather red colour. Also the timing influenced on the outcome; after two hours of marinating, the parchment had an overall light pinkish purple tint with dark spots where the gland had touched the skin. If the glass container was transparent, the colour became often blue with red-violet marks. Of course, the result seemed accidental, but could be influenced by the artist’s ‘tour de main’, turning the bottle over, adding more glands to the folds of the parchment or twisting it or prolonging the ‘cooking’ time. Even a tie-dye technique brought interesting results once the coloured piece reappeared from the container. Using a bottle proved worthwhile to keep glands, juice and parchment very close together. Naturally, after well rinsing the piece, it needed careful stretching during the drying period.
Every single work turned out different; the more sophisticated the recipe, the more fascinating the result. All possible hues of purple occurred and the shapes of the glands where they touched marked a delicate design: the fine trace of the slightly curbed organ was visible. One time the entire skin of a lamb was treated with Murex brandaris leaving behind red purple crescents. When the recipe was repeated on the same skin with Murex trunculus, blue signs appeared wherever a gland had contacted the parchment.
Colouring parchment can also be done by applying the purple liquid directly. The sheet needs to soak in water for a while; adding a drop of detergent helps the colour to adhere better. It is then stretched on to a small canvas and ready to receive the first layer of the ink-like juice. This is collected from the cut-out glands laid in a small amount of water. After a few hours they have rendered most of their colour, and are then sieved off. The remaining purple liquid may serve for writing using a fine hairbrush. If it is thickened by a small addition of talcum, which slightly modifies the hue, it has covering qualities and can be easily brushed on parchment, paper and canvas.
Even without talcum the purple juice is an interesting medium used as a watercolour on any support. It is applied layer by layer. Each layer needs to dry before the next one is added. After about fifteen for parchment, twenty applications for paper or even more for canvas, the material is saturated. A strong purple violet, evenly spread, with the typical ocean smell once it has dried completely, is the beautiful result. Gold or silver writing on such purple parchment would simply look marvellous.
At this stage a purple powder was obtained which recalls the famous purpurissum in Pliny’s writings.(Pliny). As the creta argentaria was not at hand, talcum turned out a valid substitute; it was added to the purple liquid and then dried in a Petri dish giving a light violet coloured powder which could be darkened by repetition. Was this the pigment?
A third possibility for colouring parchment is treating the skin in a dye-bath similar to textile dyeing. The wetted sheet is dipped into a cold purple fermentation vat for a few hours. In most cases the result is a mainly blue colour, rarely a violet one, as it is difficult to avoid light entering the vat. In all of the above-mentioned techniques the soaked parchment needs careful stretching during the drying process.
It is important to say that these experiments were carried out with Murex trunculus. As this snail is fast in developing good quantities of the purple hue, working that is painting or writing with it can start immediately. Murex brandaris, on the other hand, has tendency to react very slowly, sometimes not at all. According to season they even will not exude their secretion or in such minimal quantities that they become useless.
Despite the progress and insights, pure dry pigment was still not in sight. Only further examples for ‘wet painting’ in the South American history of non-structural textiles emerged. The Pacific sea-snails (i.e. Purpura patula, Conchelepas conchelepas) seem most attractive for this technique. They need not die, they can be ‘milked’ and the juice is plentiful. Besides using this purple for staining cotton strands or dyeing textiles, the colour seems to have been employed for painting. Quoting Zelia Nuttall (1909) as witness:
“In the ancient Mexican codex which belongs to Lord Zanchu, ( now called Codex Nuttall ), a beautiful purple paint is profusely used. It contains pictures of no fewer than thirteen women of rank wearing purple skirts, and five with capes and jackets of the same colour. In addition, forty-six chieftains are figured with short, fringed, rounded purple waist-cloths, and there are also three examples of the use of a close-fitting purple cap. Moreover, the codex also contains representations of thirteen personages whose bodies and faces are painted purple, and five whose bodies only are purple, their faces being painted with other colours. In one case it is a prisoner who is thus depicted. In another a wholly purple person is offering a young ocelot to a conqueror, an interesting fact, considering that ocelot-skins were usually sent to the Azetec capital as tribute by the Pacific coast tribes of southern Mexico.
The shade of the purple paint used is identical with that of the purpura dye, and until it is demonstrated to us that the native artists obtain this colour from some now unknown mineral or vegetal dye, it may be assumed that they also used the purpura dye in preparing their paint in depicting personages with body paint and garments dyed by means of the same shell-fish.”
Zelia Nuttall concluded that the purple of the old Mexican manuscripts was authentic.