Acord of sky blue thread – called “techelet” in the Bible – must be tied among the ritual fringes worn by observant Jews (Numbers 15:37- 40). Despite the frequency with which this command is repeated – it’s part of the paragraphs following the twice daily obligatory recitation of the Shema – the secret of creating the required specific blue was lost for more than a millennium.Rather than use the wrong color, plain white fringes were substituted for blue ones.Techelet had additional uses in ancient Israel, but it always connoted status, prestige and wealth. According to the Talmud, the sole legitimate source of the techelet dye is the marine hilazon, identified by most as Murex trunculus or banded rock murex, a kind of snail. But despite intense research and experimentation, until recently the ancient technology couldn’t be achieved by contemporary scientists.The Rarest Blue tells you everything you ever wanted to know and more about this elusive color and the odyssey of its rediscovery. Enlivening this scholarly, encyclopedic description of the color are the vicissitudes of the drama of the search.Author Baruch Sterman is a physicist who helped develop the modern blue dying techniques, and a cofounder of the Ptil Techelet Association. He and his wife Judy Taubes Sterman, whose kitchen was an early laboratory for the experiments, are a talented and knowledgeable writing team.For example, they raise the question of the discovery of the Murex trunculus shells amid the excavation on Mount Zion, the westernmost section of Jerusalem in the Second Temple period.Jerusalem is, of course, landlocked.What were a few dozen shells doing amid first-century artifacts from the time when the Temple of Herod stood? Archeologist Shimon Gibson, one of the many experts consulted in this story, suggested that the shells were brought to Jerusalem for advertising.Blue dye was in demand in the Temple because priests needed to color wool and the same retailers would be selling ritual fringes to the general population.“Perhaps, as a striped barbershop pole advertises haircutting services, a snail shell outside a door declared to the public, ‘techelet sold here,’” said Gibson.The shells would have provided authorization that genuine blue was for sale, and not fake blue strings, known as kala idan. The Talmud issued ominous threats to unprincipled dealers who might sell counterfeit blue dye.The imitation, created from plantderived indigo, looked identical to the snail-derived blue. Something like slipping a zirconium instead of a diamond into a royal tiara. But unlike the stones, techelet couldn’t be tested. Today there is a test.Half a century after Yigael Yadin excavated Masada, a scrap of cloth from the dig was examined by chemist Zvi Koren of the Shenkar College of Engineering and Design, now in Ramat Gan. In 2011, Koren confirmed that the dark blue embroidered stripe on the cloth had been colored with dye from murex trunculus.DYE MASTERS of ancient times were held in great esteem. The Jerusalem Talmud reports that they walked around with a wool tuft behind their ears to advertise membership in their elite guild. Rightly so. Dyeing in ancient times was a complex occupation.Color had to last through washing and sunshine. The dyer had to find a chemical ploy that would allow dye to enter the fabric, adhere and lock in.The dyes were harsh and stank, particularly with dye from snails. Dyeing with murex secretions meant working very fast before the color changed and using large qualities of snails; 7,000 for a single pound of wool.After the destruction of the Temple, there was no more priestly service, and the manufacture of blue cloth needed by the priests ended. Jews in Palestine and the rest of the Roman Empire continued to follow biblical commandments to wear techelet strings on the fringes of their garments. But soon the special blue fell under the category of “purple cloth,” restricted to royal production, forbidden to be sold by commoners. Even if they could get techelet, it was prohibitively expensive. Plant-derived indigo became the common source of blue. Hence, the tradition of wearing the blue strings as well as the knowledge of producing it disappeared almost completely in the seventh century.Until modern times. Numerous learned aficionados have devoted themselves to the revival. The most famous of them was Rabbi Isaac Halevi Herzog, who earned his doctorate investigating what he called “porphyrology.”His thesis was called The Dyeing of Purple in Ancient Israel. In it, he debunked the conclusions of Rabbi Gershon Henokh Leiner of Poland, the Radzyner rebbe, who had researched the subject in the 19th century. But Rabbi Herzog himself erred in his refusal to accept the Murex trunculus as the source of biblical blue because it seemed to produce only purple, and not blue dye.The conundrum was resolved by Otto Elsner, a dye chemist from the Shenkar College. To cope with the rancid smell of the snails, Elsner set up his lab bench near an open window. Serendipitously, on bright sunny days, when the dye was bathed in Israeli sunshine, it turned sky-blue.The next challenge was to make blue ritual fringes, creating first a cottage industry and then a more commercial production line. For the first time in 1,300 years, techelet fringes were once again available, allowing persons to fulfill the biblical commandment.On one hand The Rarest Blue indulges the reader in lofty reveries about the nature and philosophy of blueness.“It’s not mere coincidence that the techelet string hangs specifically from the edge at the corners of a garment.The blue thread emphasizes the importance of man’s acceptance of his mission in life and his commitment to moral and spiritual directives.”On the other hand, the book provides intriguing descriptions of the hands-on process of making the dye and fringes, from the gathering of the marine snail to the intricacy of fringe-tying. There’s even a suggestion for a home science experiment.The Stermans are themselves among the knights on this noble quest. The Rarest Blue has been written with the same energy, erudition and delight in Judaism that characterizes the mission.You’ll want a copy in your personal library. ■
