By 1980, there appeared a number of specialists in ancient dyeing, who were sure that Tekhelet and the Tyrian purple were the same. Among them were Israeli scientists who tried to prove it. I.I.Ziderman developed theory that different species of Murex give more reddish and more bluish color. The latter could be Argaman and the latter Tekhelet, according to Dr. Ziderman. This bluish color had been obtained as early as 1832 by Bizio. The greatest problem was the color – not blue enough. In 1985, prof. Otto Elsner, a specialist in dyes, together with marine zoologist Ehud Spanier, found the the color depends on sex of mollusks. Later they published breathtaking news: they succeeded obtaining a blue color dye from the species Murex trunculus (Argamon kehe-kutzim)!
The main result was that the dyeing in intensive sunlight resulted in blue, whereas the dyeing during a moderately bright day or in a room resulted in purple. These results were in essence printed in German already in 1944 by Driessen. After some investigation, it turned out that a photochemical process was involved that results in a partial loss of bromine atoms.
A mixture of dibromo-, monobromo-, and plain indigo emerges, as shown by Prof. Zvi Koren. The loss of bromine makes the color of the dye less deep, as the theory predicts, and it turns out to be blue rather than purple. The processes in secretions of mollusks are not simple, though. The percentage of bromine appears to depend on the snail’s sex, and it varies during the life of the mollusk, as was discovered by Elsner and Spanier. The fraction of bromine and so the color to be yielded also depends on the exact species in the family.
Another important character of the story is Rav Eliahu Tavger. He is the one who produced the first tzitzit dyed by snails from northern Israeli beaches and proclaimed them to be valid from the point of view of the Jewish law. (Interestingly, the late father of Rav Eliahu prof. Benzion Tavger restored the “Avraam Avinu” synagogue in Hebron, basically single-handed).
There are two ways of dyeing Murex dyeing technique can be implemented in two ways – from fresh snails, using natural indigo precursors, or from a dry extract. The former is not practical in big quantities, while the latter requires the vat process. The vat dyeing has been run smoothly enough for several years but it employs some modern chemicals, the favorite one being sodium dithionite Na2S2O4. The fact that no such things could be used by the ancient renders the idea somewhat doubtful.
Then, in 1995, Dr. Cardon found and translated a 1418 Florentine recipe for a vat process that used an indigoid plant called woad. This technique involved fermentation. During the process, leaves were put in hot alkaline water for a while, and then the resulting liquid became capable of reducing indigo. Research showed that in these conditions, a bacteria of Clostridium family developed, and the process was not purely chemical but rather microbiological. The foundation “P’til Tekhelet” learned about the breakthrough and sent the dry extract of snails to several people, asking to repeat the process. One of them was John Edmonds of England, a retired engineer who had been interested in ancient dyeing for years; another was Prof. Zvi Koren at the Shenkar College in Israel. Mr. Edmonds found that woad fermentation was not good, since it brings its own indigo in and obscures the results. So, he turned to fermentation from cockles’ meat, as he was short on the Murex. In 2000, it was finally clear that Mr. Edmonds succeeded not only in dyeing but also in restoration of the process described by Pliny the Elder. It also turned out that what Pliny described was not only dyeing but also fermentation and reduction of indigoids into a yellow solution of leuco-base . The conditions of the process – alkaline, heat, and high amounts of salt – enable the growth of the desired bacteria while preventing the growth of others. In that same year, Prof. Koren succeeded in developing a completely natural dyeing method, using an all-murex system for both the reduction and the dyeing stages, which also made the dye production highly efficient.
Wool put in this yellow leuco-solution absorbs the chemical; when taken out into the air, it turns purple or blue, depending on the intensity of light and other factors, as originally shown by the late Prof. Elsner.
It turns out that for all practical purposes, The Modern-Ancient Tekhelet industry was restored about 3 to 4 decades after the founding of the state of Israel. The theoretical research of Bizzio or Driessen before the founding of the state of Israel was on the practical level not enough to start getting the Biblical commandment restored. It was the research of Elsner, Spanier, and Ziderman that convinced some of the Rabbinic world to wear Tekhelet derived from Murex Trunculus.
The Video https://www.torahanytime.com/#/lectures?v=44553