Tekhelet Perception

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by Dr. Baruch Sterman

While I am always thrilled to see the issue of tekhelet being discussed (Tekhelet: Color Perception or Apprehension, Efraim Vaynman), and certainly in such a thorough and thoughtful way, I feel the need to clarify my own position and correct several mistakes. Harav Eliyahu Tavger, the founder of our non-profit Ptil Tekhelet organization, has pointed out that the mitzvah of tekhelet was born in machloket. The very next thing that happened after it was given was that Korach used it to build his argument against Moshe. Rav Tavger has guided our organization with a very clear directive: to minimize machloket regarding tekhelet as best we can. We welcome advice, criticism, dissenting opinions, and even rejection of reinstituting the mitzvah of tekhelet, but we fervently hope that this be done in the spirit of machloket l’shaym shamayim.

The issues surrounding tekhelet are complex and nuanced. The sources, often contradictory, are vague at best and subject to interpretation. To suggest that there is any attempt to white-wash the controversy or uncertainty regarding the color of tekhelet, and moreover, to state that I try to “deceitfully tell a different narrative,” is out of place, to say the least. In my book, The Rarest Blue, I write:

“Throughout this book, we will describe the color of tekhelet as sky blue or azure. As will become clear, this is not a universally accepted position, and it certainly wasn’t the consensus opinion among scholars before the 1980s. Some scholars maintain that the hue tended more toward violet, a blue purple. The depth of the color is also debated, with some claiming it was a darker shade of blue. The reasoning that leads to the opinion that tekhelet is the color of the clear, cloudless, midday sky will appear later in the book.”1

Moreover, Ptil Tekhelet has no vested interest in promoting one shade over another. Our goal is to provide murex-dyed strings for tzitzit. We do not have the luxury of leaving the issue of the color of tekhelet unresolved. At the end of the day we are the ones who are making the actual strings available for the hundreds of thousands of Jews around the world who tie it onto their tzitzit. We have had to make decisions and settle on a target color, not only hue, but depth as well. This we have done according to the direction of Rav Tavger, in consultation with numerous Rabbinic authorities. The motivations behind our organization should not be in question.

I am glad that we are in agreement with Efraim Vaynman regarding most of the issues at hand. We both accept that the Murex trunculus is most likely the hillazon source of ancient tekhelet. No one can deny the fact that it is possible to obtain a sky-blue dye of lasting quality from the Murex trunculus snail using only methods and ingredients available to the ancients. Ancient dyers appear to have known that this was the case, as indicated by the Wadi Murabba’at textile and the Pazyryk saddlecloth (and even the Masada piece). Furthermore, it is highly likely that over the more than 2000 years of murex dyeing, here and there the wool would have come out a sky-blue color. Mr. Vaynman presumably concedes that the dyers knew they could tweak the color (by photodebromination or other means) and is simply asserting that the tekhelet dyers did what they could to make murex dye blue-ish, but were not exacting in the requirement that their tekhelet be 100% violet-free. Mr. Vaynman believes that the target color was a dark blue with a violet tinge, and I lean towards what we call sky-blue.

I would like to turn to specific points relating to Mr. Vaynman’s position:

  • Halachic Considerations for sky-blue: Leaving aside for the moment what the ancient dyers sought to achieve, the trend among halachic authorities throughout the ages heavily leans towards sky-blue. This is the position of the Rambam (taking the plain and straightforward reading of his words) in both Hilchot Tzitzit (2;1), “דמות הרקיע הנראית לעין השמש בטהרו של רקיע” and Hilchot Kli Hamikdash (8;13), “כעצם שמים שהוא פתוך מן הכוחל”. Although the Rambam elsewhere talks about “shachor”, his son nonetheless, interpreted his father’s position as presented here.2 Likewise, this opinion is shared by the Radak,3 Rabbenu Bahya,4 Saadia Gaon,5 and many others. Among the later halachic sources, the Tiferet Yisrael, who had a profound influence on the Radzyner in his quest to rediscover tekhelet, states the matter clearly and unequivocally. Referring to Wilhelm Gesenius’ identification of tekhelet with the color violet, he writes:

אמנם במה שכתב שבדם החומט צובעין “פורפור בלויא”, דהיינו “דונקעל בלויא”, בזה לא נשמע לו, דעל כרחך זה שלא כקבלתינו, דהרי חז”ל אמרו תכלת דומה לרקיע (מנחות מ”ג ב’), וכך כתב הרמב”ם שהבאנו שצבעו כטוהר הרקיע נגד זריחת השמש, והיינו “העללס היממעל בלויא”.6

However, with respect to what he [Gesenius] wrote that the blood of the mollusk dyes a “purple blue”, that is “dark blue”, in this we will not heed his [opinion]. For this is certainly against our tradition, as our sages said that tekhelet is similar to the sky (Menachot 43b), and so wrote the Rambam that we brought before, that the color is as the pure sky opposite the shining sun, and that is “light sky blue.”

These sources form the basis for our halachic decision to seek sky-blue as the ideal shade and hue for tekhelet. This decision was made in full awareness that there are many who hold differently, and the spectrum as to the color of tekhelet varies widely from green to violet to midnight blue and, of course, sky-blue. It may well be that the exact color/shade is not mi’akev – invalidating the fulfillment of the mitzvah.7 Again, it could certainly be the case that the ancient dyers had different criteria, but given the fact that we are able to obtain this exact color from the murex, it makes sense within the halachic framework to aim for that outcome.

  • Regarding Rav Herzog’s objection to the Murex trunculus as the tekhelet hillazon, a pertinent fact must be elucidated. I would like to invite readers to compare two tufts of wool dyed from the Murex trunculus under precisely identical conditions, differing only in that one was exposed to sunlight and one not. Here is a picture: link. The tuft of wool on the left is what everyone before 1985 would have known to be the color that is produced by the Murex trunculus snail. The question, especially with respect to Rav Herzog’s work, is would that color have been called tekhelet. As previously mentioned, the Tiferet Yisrael railed against the identification of the hillazon with Gesenius’ snails because those snails produce purple and tekhelet must be blue. Furthermore, Rav Herzog received these unequivocal assertions from his most trusted authorities: Paul Friedlander – “I also consider it impossible to produce a pure blue from the purple snails that are known to me.”, and the Goeblins Laboratory – “I don’t know of any natural blue colour other than indigo that is capable of solidly dyeing textile fibers.”8 While Rav Herzog may have entertained the fact that tekhelet was a darker blue, he was certainly skeptical about whether the murex could provide even that as opposed to purple.On this point, I would like to note that Rav Herzog’s use of the term “dark blue” is probably not what Mr. Vaynman assumes – namely a midnight blue with hints of violet. He specifically states in his doctorate the contrast between “light sky blue (helles Himmelblau)” and “dark sky blue which is the color of the cloudless Palestinian sky in bright sunshine.”9 It is precisely that color that we aim for in our tekhelet strings.
  • It is easy to get blue from the murex: We have been dyeing tekhelet for over 25 years. Hundreds of thousands of sets. Once you know about using sunlight and steam it is in some ways easier to get blue (maybe with a hint of violet here and there) than it is to get purple. I have enough respect for the ancient dyers to assume that they would have recognized the influence of sunlight during the more than 2000 years of murex dyeing. There is no doubt in my mind that they would have noticed the fact that subsequent batches of wool dipped in the same vat would produce sky-blue. To assume, as Mr. Vaynman does, that the ancient Tyrian dyers who provided the tekhelet for Shlomo Hamelech’s Bet Hamikdash would never dare to double dip, being worried about a machloket in Menachot regarding Maareh Sheni, is an anachronism to say the least. But were one to take that position, the matter is still not closed. Perhaps the ancient Phoenician poskim held like the Tanna R’ Yochanan ben Dehavai who permitted Maareh Sheni. Or maybe they adopted the shitta of Tosafot or the Rambam who likewise permit it under certain circumstances. Even if those sages held like Rashi, then maybe they understood his opinion as did the Tshuvot Hameyuchasot L’Rashba, or as the Radzyner explains it.
  • Evidence for dyeing blue with Murex: Mr. Vaynman makes no mention of the Pazyryk saddlecloth which has a sky-blue murex dyed border dating back to the 4th-5th century BCE. The murex can produce a sky-blue dye, and it seems clear that the ancients had the knowledge and technology to realize that. One can assume that Chazal knew what the dyers of their time knew as well.
  • Elsner’s part in the discovery: Mr. Vaynman takes umbrage at our “narrative” in that I “inexplicably” attribute the discovery of the debrominating effects of radiation on the reduced vat to Otto Elsner instead of to Driessen. Indeed, in footnoting the serendipitous discovery that Elsner made I write:

“This is one version of the apocryphal stories of the serendipity that led to Elsner’s discovery of the photochemical processes that debrominate snail dye. It may not have been completely accidental, though, and Elsner may have been looking for such effects. As an experienced indigo dyer, he knew that dyeing in direct sunlight could change the color somewhat. He also may have seen the paper by Driessen, who first suggested this phenomenon (Driessen, “Uber Eine Charakterische Reaktion Des Antiken Purpurs Auf Der Faser”).”10

The reasons I favor the version giving Elsner the credit are:

  1. I have not found any indication (though Mr. Vaynman and Gadi Sagiv make this claim) that Elsner himself gives credit to “2 German Chemists”. Furthermore, to the best of my knowledge, he never cites Driessen’s work.
  2. In his original paper (1985) Elsner shares his thought process. “It is a known property of some vat dyes to change their color when exposed to solar radiation when reduced to their leuco state.” He then goes on to quote the work of Weber, Goldstein and Gardner who showed that “halogenated vat dyes may lose their halogens when exposed to solar radiation.”11 All this led Elsner and Spanier to suspect that this might work for the brominated indigo of the murex dye. Then they tried it, and the rest is history. This first-hand account describes innovative thinking, cross-reasoning, and thoughtful application to different circumstances – all sprinkled with a bit of luck. This is not simply repeating someone else’s experiment.
  3. Driessen’s work, to the best of my knowledge, played no part in the foundational tekhelet research done in the 1980s by Dr. Israel Ziderman, Rabbi Bezalel Naor, Rabbi Menachem Burstein, and Rabbi Eliyahu Tavger. Elsner’s work did.
  • Kala Ilan and indigo: Mr. Vaynman proposes that when the Talmud equates the color of tekhelet with that of Kala Ilan (= indigo), it means a violet indigo. After all it is possible to obtain that color from the indigofera plant under certain conditions. Keep in mind that Isatis (= woad) is also equated with the color of tekhelet. Again, presumably, the argument would be that this could also be dyed violet. All true. But there are countless examples of blue indigo-dyed fabrics dating back to the time of Tutankhamun. The Talmud is most likely comparing tekhelet to the common color that indigo dyed, not one achieved by some atypical recipe. As we know from myths around the world, from art, etc., indigo was widely associated with the color of the sky. Mr. Vaynman wonders why anyone would use murex to dye blue when they could obtain the same color from the cheaper indigo plant. This is like asking why someone would want a genuine diamond when he can get a synthetic one for cheaper. Furthermore, this question still stands even according to his proposal that both indigo and tekhelet yield violet.
  • The Mesopotamian/Accadian context of the word takiltu (= uqnu) cannot be ignored. It is translated as lapis-lazuli colored wool. True one might argue that lapis can range from light to dark blue, but it is important to note that in the Mesopotamian cosmological myths as well as in art, lapis forms the lowest side of the heavens, and is what we on Earth see as the sky. Thus it would be more correct to associate that word with sky-blue.
  • Eye-Witness Account: The 4th-5th century paytan, Yossi ben Yossi lived in Eretz Yisrael, was a Kohen, and undoubtedly saw tekhelet firsthand. In his poem recounting the service on Yom Kippur, Azkir Gevurot Eloha, he describes the M’eil of the Kohen Gadol which was made of pure tekhelet as follows:

    עטוי מעיל תכלת כזהר הרקיע
    Wrapped in a coat of tekhelet as radiant as the sky

It would be a stretch to call violet or midnight blue, “as radiant as the sky”, and rather this implies a mid-day sky-blue.

Which brings us to the crux of the matter: Was tekhelet associated in the eyes of the ancients and in the eyes of Chazal with the sky? Maybe at times it came out more violet and at times more blue, a little lighter or darker, but ultimately we would like to know what they thought about when they looked at their tekhelet strings. What did tekhelet evoke? Countless midrashim and drashot over the past 2000 years testify to the notion that tekhelet reminds one of the sky. I can entertain the possibility that the ancient eye was less exact in its perception than ours is today, and that Jews in earlier times were more inclusive and assumed a wider spectrum in their definition of “sky-colored” than we do. But the important thing is the association with the sky. Today we have a relatively narrow definition of what we would call sky-blue, and it is possible to obtain that very color from the Murex trunculus, the legitimate chillazon and authentic source of tekhelet. The ample support indicating that sky-blue was included in the definition of tekhelet by the ancients, along with the preference shown for that color by so many halachic authorities, more than justifies Ptil Tekhelet’s decision to target sky-blue as the color for tekhelet strings used in order to fulfill the commandment today.


  1. The Rarest Blue, Lyons Press, CT, 2012, p. 222. 

  2. ר’ אברהם בן הרמב”ם עה”ת (פ’ תרומה) “תכלת הוא ממוצע בין כחול העמוק ללובן”. וכן בס’ המספיק לעובדי ה’ לר’ אברהם בן הרמב”ם, “יהיה מצמר כחול, זך, הדומה לצבע הענן הנדמה לעין שהוא צבע השמים. 

  3. ספר השרשים לרד”ק תכל – פתיל תכלת (במדבר טו, לח.), ותכלת וארגמן (שמות כה,ד), הוא העין שקורין לו בלע”ז בל”ב [אזורו אולטר”ו מארי”ן.] 

  4. רבינו בחיי שמות פרשת תצוה פרק כח (ו) ועשו את האפוד. – …ה”תכלת” הוא הצמר הצבוע כעצם השמים. 

  5. פירושי ר’ סעדה גאון על התורה (תירגום ר’ קאפח) פרשת תרומה כה (א) ותכלת – ‘אסמאנגון’. ובהערה של הרב קאפח – כצבע של השמיים בבהירותם שהם תכולים מאד ונוטים לשחרות 

  6. תפארת ישראל כללי בגדי קודש של כהונה 

  7. שו”ת רדב”ז חלק ה סימן מח וי”ל שיש גוון תכלת שהוא שחור הרבה ויש שאינו שחור כל כך. 

  8. Most people overlook the importance of these correspondences, and usually skip them altogether since Rav Herzog left them untranslated in the original German and French in his doctorate. 

  9. Herzog, The Royal Purple, Keter, Jerusalem (1987) p. 62 

  10. The Rarest Blue, p.239. 

  11. Elsner, Otto, The Dyeing with Murex Extracts, an Unusual Dyeing Method of Wool to the Biblical Sky Blue, Proceedings of the 7th International Wool Textile Research Conference, Tokyo, 1985 Vol. V 

About Baruch Sterman

Dr. Baruch Sterman is a co-founder of Ptil Tekhelet.

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