After working a few years with other colours and especially with plant indigo, the purple topic was revived at the beginning of the 1990s. By this time, the author was living in Provence, France and discovered that Murex trunculus was sold as ‘escargot de mer ’at local markets. So the work with purple continued.
A pigment usually has the function of filling in spaces, of colouring a shape between outlines. The colourless secretion of a Murex snail however defies the use of a normal pigment.
Yet what can a painter do when the ‘colour from the sea’ refuses to become a dry powder? The obvious answer is: use it in its natural state!
Synthetic purple pigment, if one can afford it, appears ‘sterile’ compared to the colour produced from fresh Murex. The snail contains in its body a secretion of a most complex nature, carrying the precursor of a colour. This colour needs to be created, i.e. made visible, by the help of a person, a dyer, an artist, someone who knows the method. And this, for an artist, is exactly the moment or the chance to discover a different approach, the possibility of a new expression, to explore the unknown.

In order to bring to life the so-called ‘royal purple’ the snail has to die. The hypobranchial gland, which contains the precursor of the colour, is found diagonally opposite the shell’s natural opening . When the shell is broken and the gland exposed to air and light, the originally transparent mucus enters a metamorphosis from pus-like yellow, to green, to indigo blue, and finally to one of the many violet nuances. Only the artist or artisan at work is witness of this astounding transformation.
If each animal is treated separately, the different purple nuances become clearly visible. This observation inspired a technique for working with Murex in pictorial art. A snail was opened by help of a small hammer and then placed on a support. Old bed linen from past centuries with their worn, soft fibres were extremely suitable to catch the seawater-drenched mucus. The juice soaked the surface in a spectacular way: large patches with a strong blue or violet in the centre where the gland touched, appeared on the textile. Similar to the batik technique, melted wax was applied beforehand to control the running of the watery substance. This provided a means for keeping all purple stains together as wanted for the composition. At one occasion hundreds of cracked-open Murex were placed along both sides of the seam of a particularly worn, heavy linen. All of the watercolour tended to strive for the outer edges away from the central seam, thus forming an oval symmetrical pattern.
The artist is the ‘chef d’orchestre’, directing the snails, supervising the time they need to leave their mark on cloth or paper. Even coffee filter paper proved a good means of catching every single coloured molecule and, once opened, reminded of a beautiful fan.
Later those paintings were called ‘sea-water-colours’ or ‘aquarelles d’eau de mer’, a
title they earned well. As they are drenched with the ‘colour from the sea’, they will keep the ocean’s smell once they have dried.
Besides linen, paper turned out to be another interesting support. It made it possible to follow the colour’s coming into being. With a pencil the time and shade was marked next to the snail’s body from the moment the pale mucus touched the surface. Then, when yellow appeared, the second annotation was written down. And so forth, until all the colour performances were through. With Murex trunculus the purple evidence came after half an hour; with Murex brandaris however it could take two days if there was no sunshine.

The fascination with purple is certainly linked with the mystery of its past. With its provident transformation entirely dependent on air and sunlight, purple finally manifests itself in many nuances, among which a people chose a single one: tekhelet, the blue purple, in order to represent the highest abstraction man has been able to invent. It is the Biblical Blue mentioned in Numbers 15, 37-39 (King James Version) when Moses ordered his people to wear a blue thread (tzitzit) in their tassels to remember and obey the commandments of Yahwe.
Why was tekhelet to be chosen of all colours?
“Because tekhelet is like the sea, the sea is like the firmament, the firmament is like the sapphire, the sapphire is like the throne of glory.” (Rabbi Meir)
Four threads in the four corners of the tallit, the fringed prayer shawl, were dyed blue up to the 6th century. After 760 A.D., the process for the dye was definitely lost and the fringes have been plain white ever since because, according to religious law, tekhelet could not be substituted.
A Jewish mystic, Gershom Scholem, indicates that tekhelet, the blue purple within the thread of the tassels symbolizes the presence of God including the dark power of the ‘Schechina’.(Scholem 1980).
Again the remarkable fact that colours were so close to religion, to believes, to spirituality altogether is apparent. This one in particular had nothing in common with an ordinary pigment. To identify tekhelet, the sea and the sky –colours of no own substance- were used in comparison.
“As each individual has his own garment, his shawl or tallit, each time he wears it, his personal relationship with God is reaffirmed through the presence of a colour that recalls the law.”(Cixoux, Derrida 1998). It seemed the most spiritual colour of all. Again, like in the Indian colour manual, spirituality was the driving force. From the bare material, a snail’s secretion, the quest for the highest abstraction was launched. “How could a colour lead you from the perceptible to the realm of the invisible?” This question of Tekhelet is treated by Bernard Dov Hercenberg “as a colour of the crossing through the appearances, the memory and the divine. It is as if nature is offering, from the sea to the blue of the sky, a directional continuity and a perspective towards the ultimate.” (Hercenberg 1998).

Inspired by the newly published doctorate thesis by Isaac Herzog (Spanier 1987), the author embarked on its exploration. Here again, work had to be done with the organic matter, the sea-snail. Was it possible to stop the colour’s evolution at the blue stage? Experiments in this direction were all negative.
Then, in 1993, the author received an article printed in Bayer Berichte (47/1982) in which Hans Wagner, director of the laboratory of colorants in Leverkusen published the result of a series of tests. They concerned the ‘Fabric of the Three Kings’ (Dreikoenigsstoff) from the shrine in the cathedral of Cologne, and were meant to determine whether or not it contained true purple. Chemical tests proved the presence of dibromoindigo and Wagner was able to date the precious textile. The article included a series of photographs explaining the procedure. The last picture clearly showed a blue thread. How was this done?
When contacted, Wagner was very helpful, advising the reduction method of Driessen-Hengelo which he used. (Driessen-Hengelo 1944). Despite the technical difficulties for an artist who is not a chemist, a trick was found which worked: the violet traces left on soft paper, were cut out and put into a glass jar to which water, ammoniac and some hydrosulfite was added. With the lid closed, the jar went into a double boiler and was heated. Soon the liquid turned yellow, the purple stains too. Shortly afterwards, the paper parts were extracted from the liquid, then placed on a thick sheet and exposed to sunlight: what had been violet and reduced to yellow, now turned into green and then blue - indigo blue! At that moment they needed to be rinsed with water, which added to the composition as the paper pieces floated about and had formed their own pattern when the water hose stopped. There it was, the first work on paper with very distinct traces of so called ‘tekhelet’.
Who could decide whether this was ‘tekhelet’ or at least whether the name could be used in an exhibition? A letter was addressed to Otto Elsner in Israel whose research on the Biblical Blue is widely known. (Elsner 1991). He replied (June 2, 1993) referring to the comparison of tekhelet to the sky: “Since the sky is blue, there is no question – at least for me, that tekhelet describes what is today called ‘sky blue’. The sky blue varies, for ex. in Europe it is paler, in Israel it is darker resembling more indigo. There are also times that red is mixed in, creating more reddish blue or violet. All this belongs to tekhelet. Consequently I don’t see any reason against using the biblical term tekhelet to describe these colours and the artistic creations.” In September 1993, the first artistic work using tekhelet was shown during a personal exhibition in Provence, France.

How far could the experience with royal purple be extended? To find an answer, it was impossible to avoid the ancient dyeing process.
In 2001, the author succeeded in reconstructing a fermentation vat using fresh Murex trunculus instead of the purple powder mentioned in John Edmonds’ book. (Edmonds 2000). Glands were cut out and soaked in water where they quickly turned into violet colouring the water as well. A glass jar with this mixture was placed into a double-boiler, some potash added to achieve an alkalinity between 8-9 pH and then –with the lid on - heated constantly for a week at about 45° C. Three days later, the liquid had turned blue-green. Under correct circumstances, the fleshy parts of the glands provoke a fermentation, which leads to a healthy dye-bath at the end of a week. Wool or silk dipped into the vat and left for a few hours, will come out green and - if the entire procedure is kept in the dark- will oxidize into a violet purple. If the dyeing is carried out during daylight, the result will be a blue purple colour. ( Boesken Kanold, 2005)

When the indigo master dyer is testing the maturity of his dye-bath, he listens to its sound, he smells the vat, he watches its surface, feels the water and tastes the liquid. The preparation of the purple colour too calls on all senses:
the pounding sound of the shells being cracked open must have been a familiar noise at the imperial factories
a purple production site was marked by the unforgettable odour of garlic and asa-foetida emanating
from the pits
only those who open the shell and extract the glands can watch the exciting metamorphosis from a transparent slimy secretion, to a yellow, green, blue, blue-violet and finally violet-red colour
the precursor-bearing gland contains a toxic substance, a piece dropped onto the skin leaves a
burn-mark similar to a cigarette bud (personal observation)
according to Rolf Haubrichs the glandular liquid tastes like acid and burns your mouth.(personal comment)

All of this can be experimented while working with fresh Murex for a dye-bath or in art. The synthetic pigment –if available- cannot compete with these emotions. The door is closed to any invention stimulated by the substance itself, by its complex subject matter.