Zvi C. Koren’s Reply to the Stermans’ Response

Continuing the tekhelet debate

In the Archaeological Views column “The Great Tekhelet Debate—Blue or Purple?” (BAR, September/October 2013) Baruch and Judy Taubes Sterman of the Jerusalem-based Ptil Tekhelet Foundation suggest that God’s chosen color for the ancient Israelites was a sky-blue derived from murex dye. In a letter to BAS, Professor Zvi C. Koren, director of the Edelstein Center for the Analysis of Ancient Artifacts at the Shenker College of Engineering and Design in Ramat Gan, Israel, criticized the Stermans’ analysis, and the letter below is part of the extended tekhelet debate on the BAS Scholar’s Study page.

<< Back to Scholar's Study: The Great Tekhelet Debate

Zvi C. Koren debates whether the strings of this Jewish prayer shawl reflect the shade of Biblical tekhelet. Photo by Eugene Weisberg/Courtesy of Amutat Ptil Tekhelet

It is troubling that the Stermans continue their distortions of facts, espousing misinformation and disinformation, even in their response to my criticism of their original article. To put words in my mouth, or in Rashi’s mouth, that were never said or written is misrepresentation. I will clearly answer the points that they raise.

In reference to my chemical discovery of an archaeological tekhelet found at Masada, the Stermans’ state that I claimed “that all tekhelet had to have been this same shade”. This is a misleading statement in that when performing natural dyeings, it is very difficult to obtain exact reproducible results with natural materials. The fact that I claim that the original tekhelet was blue-purple, does not of course indicate the exact shade of bluish-purple or purplish-blue, but it is NOT simply blue or the sky-blue of their organization. Incidentally, the archaeological tekhelet is “Jewish,” as my forthcoming article will detail. Also, it’s important to keep in mind in this discussion that both the Rambam and Rashi unfortunately never saw tekhelet in their lifetime.

As I wrote in my response to their article, and I reiterate here, their original statement that “Rashi defined tekhelet as a deep blue or dark violet” is completely false. He never wrote that and I dare anyone to find those colorful words—in Hebrew or English—in any of Rashi’s writings! It is a simple and clear fact that Rashi, in his own words in Numbers 15:41, explicitly cites the opinion of someone else (Rabbi Moshe HaDarshan) as the latter states a position different from Rashi’s. It simply makes no sense for Rashi to consistently write that tekhelet is yarok (green) and then in another instance, just a few verses after he again mentions that tekhelet is green, for him to write that tekhelet is another color – the color of the darkening skies. This latter description, by the way, is an ambiguous depiction as the darkening skies at dusk can have various shades (orange, reddish, bluish, violet, gray, etc.), which are obviously most certainly not yarok.

Click here to read about the Stermans’ article in BAR, and visit The Great Tekhelet Debate Scholar’s Study page.

My published scientific experiments with completely all-natural dyeings with the snail pigments clearly show that air must be prevented from entering the dye bath and thus this solution would have needed to be covered at all times, except for the very brief periods of gentle stirring. Their statement that “none of the ancient recipes such as those recorded by Pliny or in the Talmud mention that requirement” is completely irrelevant. The Talmud and Pliny were written as general descriptions, not how-to guides or detailed laboratory manuals for chemistry students. But more importantly, with all due respect to the Talmud or Pliny, I do not need them to tell me that the dye bath that has undergone reduction (the OPPOSITE of oxidation) needs to be covered. It is the SCIENCE of what’s possible that tells me that the natural anaerobic reduction process must be performed via the elimination of air. By the way, laboratory and industrial manuals from two centuries ago do detail how to naturally dye with indigo from plants and specifically indicate that the dye bath MUST be covered.

In the Stermans’ response, they state “Koren further implies that there is no way to achieve a sky-blue color from murex dye without modern chemicals.” I never said that. What I did indicate was that the ANCIENTS—Jewish or non-Jewish—could not, and would not, produce daylight sky-blue from the snail pigments with the methods, materials and tools available to the ANCIENT dyer. Since the Stermans themselves have obviously not performed all-natural dyeings to produce daylight sky-blue, they cite examples by two others for obtaining bluish shades. Their first example, that Edmonds used a fermentation vat to produce blue-colored wool, is completely misleading. He used a GLASS vessel for his dye bath and exposed the solution to the sun in the photo-debromination process (used by the authors’ organization) in order to get a bluish color. Glass is obviously transparent, but in ancient times the Phoenicians and their contemporaries used CLAY vats (the Romans also used metal pots), which are obviously NON-transparent. Thus, light would not—could not—have entered the solution, especially since the solution needed to be covered as I stated above. The other example that the authors cite is the experiment by Hoffman in which he produced a very light sky-blue wool dyeing. He used the fermentation vat that I had previously detailed, without citing that fact, and then he used Elsner’s method of first introducing a woolen sample into the dye bath in order to extract much of the redder—with some blue—component of the pigment. He then placed a SECOND wool sample into the SAME dye bath, which now had less of the red component than before, but also is somewhat diluted with respect to the blue component. Firstly, anyone who is conversant with the Talmud’s discussion on this subject would immediately come to the conclusion that to propose that this is what the ancient Hebrews did to perform tekhelet dyeings is nonsense. Halakhically, any textile introduced into the dye bath must be specifically for the sole purpose that the wool must be used for the dyeing of tekhelet from the beginning. To first use a wool sample to get rid of a significant amount of red component—and not to use that sample itself for dyeing it to tekhelet—would make the whole dye bath unfit (not kosher) for any further use! Secondly, this process is also implausible from a logical point of view. To collect many sea snails and process them in lengthy and complicated biochemical procedures, only to be followed by removing (or destroying) an important component from the pigment, in order to produce light blue dyeings, simply does not make any sense.

In conclusion, based on my experiments and chemical investigations of the science of this process and of the science associated with the snail pigments, the only possible color of tekhelet-dyed wool is blue-purple, as my analyses have shown that it has violet as well as both blue and red dye components. The shades could of course be referred to as purplish blue or bluish purple, but NOT blue or daylight sky-blue! So how did the ancients produce these blue-purples shades? The answers are in my article, published elsewhere.


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  • Stein says

    Dark purplish blue, blue, and bright greenish blue: Tkhelet can come in any of these colors.

    Everyone seems to agree, the shade of Tkhelet from the Murex dye needs to match the Lapis Lazuli stone. (Amazingly all quantities of this stone came from Blue Mountain in Afghanistan since prehistoric times.) Lapis lazuli itself ranges in color, from a deep purplish blue, to blue, to a light greenish blue. It compares to sky blue, which also ranges across all of these colors. It compares to sea blue, which also ranges across all of these colors, from ultramarine to aquamarine.

    Some descriptions of Tkhelet clearly have the deep purplish blue, as the sky turns toward night. Every once in while I notice this color after sunset, as the entire clear sky has an iridescent deep (dark but saturated with color) purplish blue color that I find breath-taking.

    Some descriptions clearly have a greenish blue color in mind, the beautiful aquamarine that is seen on some Mediterranean shores. This is the sky at daytime, a bright baby blue color. But it can be greenish shade of blue, like turquoise.

    And the dye being described is mainly indigo, same as American blue jeans.

    All of these colors seem Kosher, and each has traditions supporting them.

    There is no coincidence that the Tkhelet, the Murex dye, the lapis lazuli stone, the sky, and the sea, are all of these colors.

    All of these shades of indigo, from purplish to blue to greenish, are all ‘Tkhelet’.

  • Mike says

    Biblical archaeologists writing in BAR sure are more hostile to each other than they need to be. The acrimony need not be so intense. The level of self-certainly could be dialed back a few clicks on the dial. Politeness in writing could be and should be dialed up a few clicks.

  • Rose says

    This conclusion is highly intellectualized, dye made from the Muricidae sea snails is recorded for making ‘purple’, however there’s no record that Muricidae sea snails were used for making blue dye.

    Both the breast plate of Moses and the breast piece of the 18th Dynasty of Egypt were made about the same time and about 200 miles apart according to our legends.

    The Hebrew word ‘tekhelet’ is used here to describe the blue in the ephod Moses designed for Aaron.

    Exodus 28
    6 And they shall make the ephod of gold, of blue, and of purple, of scarlet, and fine twined linen, with cunning work.

    Obviously the ‘blue, purple and scarlet shown in the stones in the breast piece linked here are clearly the colors; Cyan, Purple and Red. ‘Blue’ in the Bible is light blue or Cyan, if we go by the art of the place and time..

    The Icon of the world

    This breastplate linked below couldn’t be considered ‘cunning work’ when held up to any Egyptian breast pieces. It actually just shows how short sighted and lame the English translators of the Bible really were. It appears to be designed by a 7 year old.

    Did Moses have a CO2 Laser to engrave a name in a diamond? How did that work exactly?

  • David says

    After reading the above articles and lastly Koren’s article in the AVS Publications,
    Archaeological Chemistry, VIII, chapter 3. I have to side with Zvi C Koren on this issue.
    Plus, it is always a pleasure to read technical material of an academic who can write well.

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