Not quite azure, more of a midnight blue. That is apparently the actual color of the biblical techelet, according to Prof. Zvi Koren, who spoke this week at the Shenkar College’s International Edelstein Color Symposium.

Techelet is the color that was used to dye the coat of the high priests in the time of the temples, as well as the strings attached to the corners of men’s garments “so that they may be seen and remind you of God’s commands,” as the Torah states. In modern Hebrew usage, techelet is the color of a clear sky in the daytime.

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But the analysis of a small piece of dyed fabric that archeologist Yigal Yadin found at Masada in the 1960s, dated to the first century BCE, was what Koren recently used to determine not only the true hue of techelet, but also the chemical breakdown that allowed him to establish irrevocably that the source of this ancient dye was indeed the murex trunculus snail.

However, Koren stressed that there were different types of murex trunculus.

The type used for techelet, he told The Jerusalem Post on Thursday, must be one that “not only has indigo, but is rich in it.”

As a professor at the department of chemical engineering at the Shenkar College of Engineering and Design in Ramat Gan and director of its Edelstein Center for the Analysis of Ancient Artifacts, Koren revealed over 15 years ago the origins of the biblical purplish color argaman. The techelet discovery thus completes the historic and archeological picture of the origins of the three ancient colors most important in Judaism – the crimson shani, extracted from bugs, being the third.

Even as far back as the late 19th century, scholars “have supposed and theorized that the source is murex trunculus,” Koren said. “But this never had been proven to be true.

Only now we have authenticated that the source is murex trunculus.”

The Talmud states the techelet is from a hilazon – a sea snail – and does not elaborate.

“We know most of the Jewish authorities call it bluish, lets say even with some green” – as in the case of 11th-century commentator Rashi – “but most say some kind of shade of blue,” Koren noted.

For over 20 years now, the Ptil Tekhelet association for the promotion and distribution of techelet-dyed fringes has been producing its color from the same snail. But the chemical process necessary for mass production results in a slightly lighter hue, with fewer purple overtones.

According to Assaf Stein, who is in charge of dyeing and mechanical development for the association, the difference in shade is more a matter of taste than anything else, and certainly not a halachic setback for the validity of the group’s dye.

“We try to reach a dark shade of blue, but not too dark,” he said. “It is hard to determine what the Torah meant, and seems that a singular shade of techelet wasn’t specified.

One can strive for any kind of blue that is beautiful and durable,” produced from the correct snails.

“Most people prefer the lighter blue fringes,” he added. “I myself like the darker ones.”

And since both the dye and the fabric are from natural products, and the dyeing process influenced by the temperature, quality of materials and concentration of snails, no two batches will be identical, Stein noted.

“You can actually go into a store and choose a shade of techelet you like from a variety,” he said.

Koren, who made aliya from New York 20 years ago and wears a colorful knitted kippa, stressed that he didn’t pursue this enigma from the halachic perspective. “I’m a chemist, a scientist interested in archeology, trying to find the original product,” he said. “But of course, if it has halachic applications, all the better.”

Koren, who reconstructed the ancient process of producing the dye, said his find needn’t cast tekhelet production methods in a problematic light. “I’m not a rabbi,” he said.

“But I believe that because it is so difficult and time-consuming to do a dyeing using [the technique of] natural reduction, it can be compared to the etrog citron fruit, where there are different degrees of glorifying the command, but they are all kosher.”


Koren’s take on techelet does not change the original Hebrew concept of it being a color of the sky – just what time you look up.

“This is the color of the sky, but not in daytime, rather midnight,” he said at the conference. “A midnight blue, a blue-purple. Because that’s when you reach out and feel powerless. All your senses are defenseless. That is when you see and hear the music of the night.”

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