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The Search for an Ancient Blue

The Torah tells us to put a blue thread on our tzitzit. Why has it taken 1,300 years to figure out how?

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(Zak Rosen)

In the Book of Numbers, it is written that God said to Moses: “Speak to the sons of Israel, and tell them that they shall make for themselves tassels on the corners of their garments throughout their generations, and that they shall put on the tassel of each corner a cord of blue.” Yet it is comparatively rare to see Jews wearing prayer shawls with blue thread added to the fringes. Why this intransigence?

The short answer is that it’s an extraordinarily difficult commandment to fulfill, and one over which people have puzzled for centuries. Religious Jews believe that the blue used on tzitzit must be the same blue as was used in ancient times, and the source of that blue, referred to in the Bible as tekhelet, has been shrouded in mystery for over a thousand years.

Now, thanks to the efforts of a motley crew of rabbis, chemists, marine biologists, and archaeologists from around the world, it appears the mystery has been solved. Vox Tablet sent reporter Zak Rosen to the Mediterranean coast of Israel to meet tekhelet expert Baruch Sterman, author of The Rarest Blue: The Remarkable Story of an Ancient Color Lost to History and Rediscovered, to find out why this discovery took so long. [Running time: 17:31.] 

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fascinating, especially the process of sunny vs. cloudy days. The book seems like an interesting read as well. Well-done!

Visted the factory this summer and had a demonstration of the process, very interesting and a worthwhile stop while visiting Jerusalem. Also purchased a set of while I was there.

Please note Sterman family that the clincher in doing my tzitzis was the fragment found at Masada matched chemically with the current process. Also reputably one familly from the Tribe of Zebullon had the franchise on the process proior to Roman intervention. i had the Rambom style of tying among all the possible choices. The company was P’til Tekhelet

Zorbatic says:

Just as interesting to me is how the doctrinal debates have such parallels to current Supreme Court discussions in the U.S. The rabbis here took an “originalist” approach, saying, essentially, that the word “blue” must mean the same thing it meant to the people who first wrote it. This would be along the same lines as one argument proffered in the gun control debate, that the right to bear “arms” must mean that people only have the right to own muskets or other weapons that would have been recognized by the original drafters.

    Baruch says:

    Tekhelet in ancient times did not mean the color blue, it meant the precious blue wool dyed with the secretions of sea-snails. One might argue that this should not matter today since all that is important is the color and that can be achieved in other ways. In our book, The Rarest Blue, we suggest that the Rabbis may have wanted to underscore the connection with the sea through the use of the sea creature. The midrash highlights this in its statement, “Why is tekhelet unique? Because it reminds us of the sea, and the sea reminds us of the sky…”

      Fat_Man says:

      MY understanding is that the blue dye derived from the snails is indigo (C16H10N2O2), and that it is chemically identical to the indigo dye derived from the indigo plant.

      The reasoning you quote seems far fetched to me. Many men live inland and never see the sea. Yet everyone can see the sky. No one needs to look at the sea to remember the sky.

      Can’t we accept that pre-modern people, including Jewish sages knew nothing of chemistry, and that we should adjust our assessment of things based on our knowledge?

        Baruch says:

        An important part of the significance of tekhelet was the fact that it was precious and regal. Its significance did not lie only with its color. In the ancient Mediterranean world, shellfish blue was fabulously expensive and desirable, but plant-based indigo dyed fabrics were not. Roman emperors (Nero, Theodosius, Justinian) restricted the use of shellfish blue, but not plant indigo. What makes something precious is often a matter of taste and culture. How about a synthetic diamond ring?

        There is an interesting Tosefta that should be noted as part of this discussion. “Tekhelet from a snail [hillazon] is acceptable. If it comes from another source it is unacceptable.” The next clause in that same Tosefta speaks of the gold for the Candelabra, stating that gold from scraps is not acceptable, only gold from one full block can be used. This juxtaposition implies that in both cases (tekhelet and gold) from a ritual perspective the chemical content is less important than the source.

        There have been a few Rabbinical authorities in modern times who did propose that being blue and non-fading were the only characteristics of the dye crucial for kosher tekhelet, and therefore synthetic dyes (or indigo for that matter) would be acceptable. Most authorities disagree and maintain that tekhelet must be obtained from a sea-snail.

          Fat_Man says:

          This is exhibit B in the argument of why I am not Orthodox. One might argue that the rabbis of old were doing the Jewish community a favor by so circumscribing a commandment that would be difficult or ruinously expensive to fulfill. Of course, if that were the real reason behind their ruling, it would have helped for them to say so, and to identify the tools they used to make the religion adapt to times and places.

          Modern rabbis seem to live to say no and to deny the modern world any purchase in their minds. Chemistry be damned and full speed to the rear. It is only that kind of mentality that would wear a fur hat on a 40 degree day.

          herbcaen says:

          The compound is 6,6′ dibromoindigo, not indigo itself. I am not sure whether indigo itself was known in the Old World

          Fat_Man says:

          Both plant derived and snail derived indigo dyes were well known in the ancient world.

          The dibromoindigo dye extracted from the Bolinus brandaris snail was known as Tyrian Purple and was an important symbol of imperial authority to the Roman Empire. In Biblical Hebrew it was called argaman. A related sea snail, Hexaplex trunculus, produced indigo which was was called tekhelet in BH. The two dyes are repeatedly referred to together in the portions of Exodus that describe the Tabernacle.

          A variety of plants have provided indigo throughout history, but most natural indigo was obtained from those in the genus Indigofera, which is native to the tropics. In temperate climates, indigo can be obtained from woad (Isatis tinctoria) and dyer’s knotweed (Polygonum tinctorum). The Indigofera species yield more dye.

          The Indigofera tinctoria variety of Indigo was domesticated in India in ancient times. India was the primary supplier of indigo to Europe as early as the Greco-Roman era. It was a luxury item imported to the Mediterranean from India by Arab merchants.

          Indigo remained a rare commodity in Europe throughout the Middle Ages. Woad, a chemically identical dye was used instead.

          The opening of the sea route to India by the Portugese in the 15th century lead to an increase in the supply of indigo from South Asia. Subsequently, Europeans established plantations to cultivate Indigofera in the new world.

          In the 19th century scientific chemists discovered syntheses of indigo that displaced the plant based product entirely by the 20th Century.

          Tanja Cilia says:

        the dye from the snails is chemically different from that of the indigo plant. the indigo dye is considered counterfeit for dyeing in the jewish tradition. the dye could not possibly be the same as one contains animal dna and the other plant dna – your reasoning is quite far fetched to me.

          Fat_Man says:

          No. The dyes are chemically identical. I seriously doubt that there is any DNA from the source left after the dyestuff is treated to render it usable. Baruch correctly describes the rabbinic reasoning below.

    robert zafft says:

    Apply your logic to the use of the word “papers” in the fourth amendment. Is it sensible that freedom from warrant less searches be limited to document handwritten withl quills or printed on a Gutenberg style press?

jonathan says:

explain this please…if the only reason for jews not having a blue thread in their tzitzits was because they didn’t have the right shade of blue, and now they believe they have found the correct blue, then why is it that still to this day the vast majority of jews do not have a blue thread in their tzitzits?


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Diving for Tekhelet

Photographs by Zak Rosen
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