When purple is blue

The Mosaic law commanded the Israelites to put a blue cord on the corner tassels of their garments.

“Speak to the Israelites and tell them that throughout their generations they are to make tassels for the corners of their garments, and put a blue cord on the tassel at each corner. (Numbers 15:38 CSB)

“Dyeing To Be Holy” is the title of a feature article in The Jewish Daily Forward by Nathan Jeffay. The article says that the source of the dye used to obey the command of the law has been lost for more than 1,200 years.

Roman emperors from the first century BCE onward wanted tekhelet reserved as a status symbol for the governing classes, meaning that it became progressively more difficult for Jews to obtain it. This, together with other political and economic factors, meant that by the eighth century, Jews had lost the tradition of how to obtain the dye, and tzitzit became the all-white fringes that are familiar today.

But now, a Jerusalem-based not-for-profit organization, Ptil Tekhelet, claims to have rediscovered it. “This is the experience of a mitzvah’s renaissance,” said the man leading the group of Talmud-studying snorkelers, Mois Navon, a computer programmer, ordained rabbi and Ptil Tekhelet board member. “For a biblical commandment to be returned to the people is really something significant.”

In the past, rabbinic sources have stated that tekhelet comes from a snail called the hilazon. But hilazon isn’t a biological species name, just a rabbinic name. The mystery was figuring out the species to which they were referring.

The modern search for the answer began in earnest in the early 20th century, when Isaac Herzog, who went on to become the first Ashkenazi chief rabbi of Israel, wrote a doctoral thesis in which he concluded that a snail called the Murex trunculus (the scientific name for hilazon) was the “most likely candidate” for the source of tekhelet.

Hilazon snail. Photo courtesy Ptil Tekhelet.

Hilazon snail. Photo courtesy Ptil Tekhelet.

The report continues,

Key to Herzog’s conclusion was the fact that archaeological digs uncovered large ancient dyeing facilities close to Haifa, and mounds of Murex trunculus broken open, apparently to access their dye.

But Herzog hit a snag. The snail’s dye was purplish blue, not the pure blue described in the Talmud. It took until the early 1980s for this riddle to be solved. In research unrelated to the search for the biblical dye, Otto Elsner, a professor at Shenkar College of Engineering and Design, near Tel Aviv, noticed that on sunny days, Murex trunculus dye became more blue and less purple. It turned out that the missing link between Herzog’s experiments and biblical dyeing methods was ultraviolet light, which transforms the blue-purple colorant to unadulterated blue.

Read the full article here.

There are some dissenting comments with the article.

HT: Joseph Lauer

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