Two separate fights, really, though they ran into each other. The first opened in 2001 when Dr. Mendel Singer published Understanding the Criteria for the Chilazon and argued that the Murex doesn’t answer to what Chazal describe. Dr. Baruch Sterman wrote back for P’til Tekhelet, Singer came back at him again, and R’ Yechiel Yitzchok Perr threw in objections of his own.
Stage two started a few years later. Rav Shlomo Miller looked into the matter himself and then wrote to Singer, picking up some of Singer’s concerns — the kala ilan problem above all — while opening a second front entirely: the Gemara’s account in Shabbos of extracting dye from the Chilazon. That letter got around fast, and talmidei chachamim answered it in print.
What follows tries to lay the exchanges out the way they actually happened. Evidence that surfaced years later gets its own section at the end, because reading a 2019 manuscript discovery back into a 2001 article tells you nothing about what Singer, Sterman or Rav Miller were working with at the time.
Before Singer: The 1998 AishDas Thread
People were already arguing about Murex on the AishDas Avodah list years before the Singer article appeared. The October 1998 exchange is worth reading precisely because the participants had moved past “is this a candidate” and were asking something far more practical — how do you actually wear the stuff.
Dr. Rick Turkel Z”L, a Ph.D. chemist who’d been following the dye literature for years, said flatly that he thought the identification was most probably right. His reasons: Dr. Israel Ziderman’s work, the archaeological remains of Murex dyeing installations, and the finding that material from the snail turns blue under sunlight.
Turkel also laid out Ziderman’s handling of kala ilan. Indigo is the main blue colorant in plant indigo and in Murex blue both, so on that approach plant kala ilan is passul because of where it comes from, not because its blue is a different molecule. The contrast drawn in that same thread was with Radzyn, whose finished dye turned out to be Prussian blue rather than the natural indigo tied to the snail.
Then the conversation got very concrete. Turkel wanted to know how many strings go blue and how they get tied. R’ Yosef Gavriel Bechhofer answered that he’d started out with the Raavad arrangement P’til supplied, but was rethinking the ratio, since he believed a wider body of Rishonim and later poskim held two and two.
Other things came up in passing that would occupy people for the next twenty years: whether restoring Techeiles needs a gadol signing off, whether centuries of non-use amounts to a negative mesorah in itself, and what to do with safek Techeiles when certainty isn’t on offer. For a certain slice of knowledgeable people, the Murex had already cleared the bar. Their question had shifted from “could this be the Chilazon” to “assuming it is, how do I do the mitzvah properly.”
2001: Singer Takes Aim
Singer’s Understanding the Criteria for the Chilazon ran in the Journal of Halacha and Contemporary Society in 2001. His claim was that whatever was being offered as evidence for Murex, it didn’t account for several things Chazal say about the Chilazon outright.
The Simanim
He starts where you’d expect, with the simanim in Menachos: gufo domeh layam, briyaso domeh ledag, the appearance once in seventy years, the great worth of its blood. To Singer these are identifying marks doing real work. A candidate ought to satisfy them more or less directly instead of needing each one explained away one at a time.
The Murex doesn’t, in his reading. Its soft body isn’t sea-colored, and the growth you find on the shell isn’t the animal’s body at all. Nothing about a snail resembles a fish in any ordinary sense, nobody has produced a seventy-year cycle, and the dye was costly because each snail yields a drop. Singer’s point about that last one is sharp: expensive-because-you-need-thousands is a different claim from the Gemara’s animal whose blood is precious because the creature itself shows up once in a lifetime.
Kala Ilan
The chemistry weighs more heavily on him than the zoology. Murex blue and plant kala ilan both run on indigotin as the blue colorant, yet the Gemara and Rambam give tests that separate genuine Techeiles from the counterfeit. So what were those tests picking up, if authentic Techeiles is itself basically indigo?
From that Singer draws his conclusion: the fact that Chazal could tell the two apart is itself evidence that real Techeiles has to differ materially from the plant substitute. It isn’t a side question for him. It’s close to the center of the case.
Archaeology and Purpura
Nobody denies the ancient Murex dye industry existed, Singer included. His objection is narrower than that — shell heaps and vats prove the snail supplied an important dye in antiquity, and nothing more. Whether that dye was Techeiles is a separate question that the archaeology doesn’t answer on its own.
The evidence in front of him leaned heavily toward the famous purple industry. Tying Murex to ancient purpura, he argues, doesn’t automatically tie it to the Chilazon, and treating the one as the other is where he thinks the pro-Murex literature overreaches.
The AishDas Debate After the Article
The Article Lands
Avodah picked it up immediately. The opening of that exchange sits in the September 21–October 1, 2001 thread, where Gershon Dubin announced he’d read the new piece in the Journal and Micha Berger afterward posted it with Singer’s permission.
That detail is worth holding onto. This wasn’t a critique that anti-Murex people dug up later and circulated; Singer walked into a live discussion where several of the participants already wore Murex, and his article became the spine of a months-long public argument.
It ran on through the October 5–12 exchange, the much longer October 7–November 2 thread, and a separate October 19–21 exchange about why the gedolim had stayed quiet on P’til.
Seth Mandel Z”L and the Burden of Proof
Seth Mandel came at it from a different angle than Singer did. He never claimed anyone had scientifically disproven the Murex. His argument was about thresholds: the evidence hadn’t climbed high enough to rebuild an identification after the practical mesorah had died out.
He drew a line between Techeiles and cases where one community held onto an identification that others had lost. With Techeiles there’s no such community, nobody sitting somewhere with the Murex and a tradition attached to it. Strip out the direct mesorah and archaeology and chemistry have to carry a load they weren’t built for.
So what would be enough? Mandel’s list: an animal matching the Gemara’s descriptions closely, testimony from Rishonim who still knew the Chilazon firsthand, or archaeology strong enough to tie the Murex industry specifically to Techeiles instead of to luxury purple generally. He didn’t think any of the three had been delivered. Enormous shell deposits establish an ancient Murex industry and stop there; the seventy-year line doesn’t sit well with an animal available year-round along the Mediterranean; and several related mollusks yield indigo, which muddies the claim that one species had been pinned down.
The Lavan Problem
Mandel also went after the cost-benefit framing directly. The standard pitch for wearing a safek is that you either pick up a d’oraysa or you’ve got blue strings on your tallis and no harm done.
He didn’t accept the second half. On opinions that require the ordinary strings to be white, or to match the color of the beged, blue strings that aren’t Techeiles might not function as lavan at all. That turns the trade into something else entirely: you’re not choosing between possible Techeiles and harmless decoration, you’re risking the part of the mitzvah you already know how to do.
The question kept going through the long October–November thread, with participants working over Rashi, Rambam, Tosafos, the Baal HaIttur and the Terumas HaDeshen on whether the color of the non-Techeiles strings is me’akev or just lechatchila. Nobody settled it there either.
Micha Berger: How Lost Is Lost?
Berger pushed back on Mandel’s starting premise. Did the identification really vanish without a trace? Jews stopped producing Techeiles, granted, but Jewish sources kept associating Techeiles with purpura century after century, and Berger pointed to the Aruch and later sources carrying that association forward.
An unbroken practical mesorah of dyeing and wearing that isn’t. What it might mean is that the identification survived conceptually, in which case archaeology and chemistry aren’t inventing anything from scratch — they’re supplying physical backing for something the textual tradition never stopped saying.
He also questioned whether the Menachos descriptions were ever meant to function as a zoological key. His comparison was the esrog: try reconstructing its identity from scattered remarks in Chazal alone. Once everybody in the room already knows what an esrog is, statements about its properties aren’t a definition capable of picking out the species uniquely eight hundred years later.
Here’s where the methodological split shows up clean. Singer and Mandel read the simanim as evidence against any identification that doesn’t fit them naturally. Berger and Sterman read them as remarks about a creature everyone knew, whose exact sense went fuzzy once the underlying identification was gone.
Kala Ilan Was Already Seen as the Crack in Murex
The 2001 exchange anticipated the Rav Miller controversy almost point for point. Mandel put it plainly: if Murex blue and plant indigo are chemically the same thing, it’s hard to see how the Gemara’s test separates them.
Berger’s answer was that “same principal blue molecule” and “identical dye preparation” aren’t the same statement. Historically prepared Murex dye could hold onto brominated compounds or other material from the snail, while plant indigo carries its own set of accompanying substances. A fermentation-based test could be reacting to one of those and not to the indigotin doing the coloring.
He was careful about what he was and wasn’t claiming. He never said this had been demonstrated. The claim was narrower: a shared blue molecule doesn’t by itself prove Chazal’s test couldn’t distinguish marine from plant dye as they were actually prepared.
Then he made the point that turned out to matter most. If your attempted reconstruction of the Gemara’s bedikah can’t even make known plant kala ilan fail, the problem might be your reconstruction. It tells you nothing about how Murex would do under the authentic procedure. That answer to the chemical objection was on the record in 2001, three years before the Toronto testing that became part of the 2004 fight.
Sterman Lays Out P’til’s Case
Sterman joined the long October–November thread himself. He mentioned that Singer’s article had originally been expected to run alongside P’til’s response, and pointed readers to that response.
His argument was cumulative and he said so. Murex produces a permanent blue; the ancient industry is archaeologically certain; the animal and its dye were known in the region where Chazal lived; the material has to be taken while the animal is alive or shortly after; and the same mollusks famous for purpura yield blue.
He also turned the practical question around. Citing a discussion of Rav Shmuel Ariel that sorts the possibilities into three — Murex is certainly wrong, it’s a safek, or it’s the real thing — Sterman argued that once you take either of the last two seriously, sticking with white alone stops being the neutral option. He brought R’ Hershel Schachter’s concern along the same lines, that deliberately leaving out available Techeiles could itself be a halachic problem. The framing shifts once you accept that. Adding something new needs justification, and so does continuing to leave it out.
What the Archaeology Proves
Sterman leaned hard on the sheer number of ancient Murex dyeing sites. His claim wasn’t that somebody somewhere used Murex; it was that the industry ran at a scale and in a region that makes Chazal’s ignorance of it almost impossible to imagine.
Which let him flip Singer’s question. If Murex blue looked like Techeiles and was passul, why do Chazal warn repeatedly about plant kala ilan and never preserve a parallel warning about blue coming out of this famous marine industry sitting right there?
Mandel’s answer was economic. Plant indigo was the obvious fake because it was cheap; Murex dye cost a fortune in labor and snails, so faking Techeiles with it makes no sense as a business. Proof of a huge Murex industry therefore doesn’t generate a rival counterfeit that Chazal would’ve had to address.
Same archaeological fact, two uses. Sterman read the prominence of the industry as making Chazal’s silence meaningful. Mandel read it as an ancient luxury-dye trade with no demonstrated connection to Techeiles at all.
Radzyn as Precedent
A good chunk of the thread went to whether the reaction to the Radzyner Rebbe set a precedent against restoring Techeiles on scientific and historical grounds. Mandel said the leading rabbanim of that generation mostly declined to adopt his Techeiles even though the Radzyner argued there was little to lose, and that this shows a plausible safek doesn’t automatically move established practice.
Sterman wouldn’t accept the transfer. The Radzyner’s finished dye turned out to be Prussian blue, producible from all sorts of organic starting material. Murex is an actual ancient marine dye animal and has to be judged on its own evidence rather than on what happened to somebody else’s cuttlefish in 1887.
Berger added a distinction worth keeping. One version of the Beis HaLevi objection asks how an identification could be forgotten while the animal and the technique stayed continuously available, and that difficulty lands differently on the cuttlefish than on the Murex. The other version, associated with R’ Chaim Brisker and the Rav, is much broader: science can’t recreate a mesorah once it’s lost. Accept the broad version and neither Radzyn nor Murex survives, no matter what comes out of the ground.
Underneath the snail, then, sat a much larger disagreement. The participants were arguing about what kind of knowledge is even capable of restoring a lost halachic identification.
Why the Gedolim Stayed Quiet
The October 19–21 exchange shifted in tone. Singer explained that part of what got him researching the subject in the first place was reading pro-Murex material and running into statements he thought were inaccurate or inflated.
His complaint there was about method rather than mollusks. He listed what he considered factual errors regarding cuttlefish, the treatment of Radzyn, the archaeological evidence, and claims put in the mouths of contemporary rabbanim. One example he pointed to was a published claim that Rav Elyashiv supported P’til, retracted later once it became clear the whole thing rested on hearsay.
Overstatement of that kind, Singer argued, damages the parts of the Murex case that are actually strong. If literature promoting an identification can’t be trusted to separate established fact from attractive argument, poskim are going to keep their distance, and you can hardly blame them.
He was explicit that he didn’t think the subject was silly. A marine mollusk that genuinely produces permanent blue deserves serious attention from serious talmidei chachamim, in his view. The complaint was that a potentially important case was getting wrecked by careless advocacy.
A side argument broke out over how fairly the nineteenth-century Radzyn controversy was being told. Singer objected to the picture of the Radzyner proposal getting laughed out of the beis midrash and named rabbanim who’d shown interest or sympathy. Michael Frankel disputed some of Singer’s descriptions of those supporters, Ari Greenspan said the counter-description overshot in the other direction, and the whole subthread ended up illustrating Singer’s larger point — both camps distort the history by inflating the stature, position or motives of whoever’s convenient.
Where 2001 Ended Up
Toward the end of the long thread Sterman gave a notably restrained statement of P’til’s position. He didn’t argue that every halachic methodology has to land on Murex.
Someone who holds that an unbroken mesorah is indispensable won’t accept it, and that’s a coherent position. Someone who believes the identification can be rebuilt from surviving Torah sources together with archaeology, history and chemistry may come out the other way. P’til’s job, as Sterman described it, was to make the strings available to people whose own halachic evaluation brought them there. Mandel, still arguing against adoption, called that a fair way to put it.
What makes the 2001 AishDas material durable isn’t any single proof. It’s that every question that ran through the next two decades is already sitting there: what counts as a siman, whether the mesorah was truly lost, whether science can reconstruct an identification, whether safek favors wearing or not wearing, what the archaeology proves, and how much evidence has to pile up before the burden shifts from the person changing the minhag to the person staying in white.
2002: Sterman Responds to Singer
Sterman answered in print with A Response to Dr. Singer’s Review of Murex Trunculus as the Source of Tekhelet. His central move is to argue that Singer treats the simanim with more precision than the sources themselves do.
Several Rishonim skip parts of the list, or describe the Chilazon differently when they’re discussing it elsewhere. Sterman takes the Gemara as giving a general description rather than a checklist where every phrase has to survive as an independent test.
Read that way the Murex does reasonably well. In its own environment the shell and the marine growth on it disappear into the seabed; dag covers sea creatures broadly in Chazal’s usage; and the seventy-year line may be pointing at unusual abundance or accessibility instead of a biological clock. No one of those answers proves anything by itself, which Sterman concedes. The case is supposed to hold together as a whole: the descriptions in Chazal alongside geography, ancient terminology, archaeology, the purpura industry, and the chemistry.
Sterman on Kala Ilan
On the chemistry he reverses Singer outright. Kala ilan worked as a fake because it imitated Techeiles convincingly, so similar color chemistry is the expected result rather than an embarrassment.
And when modern attempts at the Gemara’s test fail to separate the two, Sterman puts the failure on the reconstruction rather than the identification. Ancient dye preparations may well have carried source-dependent compounds, impurities and residues that don’t show up in a purified modern sample.
The Ancient Industry
He also disputes that the Murex industry points only toward purple. Jewish and classical sources tie the relevant industry to purpura, and Murex dye yields blue when handled right. Purple residue in an archaeological vat tells you what was dyed there on some occasions, not that every cloth to come out of it was purple.
2002: Singer Replies
Singer’s reply gave no ground on the simanim. A Rishon leaving out a characteristic in one halachic discussion doesn’t delete what the Gemara says explicitly, and the seventy-year statement in particular he considered a serious problem that Sterman’s answer didn’t touch.
He also refused to let the chemical test drop to second-tier status. Indigotin is the principal blue colorant in both preparations, so he saw no basis for assuming a reducing procedure would hit plant indigo and leave Murex indigo alone.
The most he conceded was this: failed modern experiments might indeed show that Chazal’s procedure hasn’t been reconstructed properly. That still leaves the underlying question sitting there unanswered. Anyone advancing the Murex owes an account of how two chemically similar blues could have been told apart by the tests Chazal describe.
Which brings the Singer–Sterman exchange to a methodological standoff. Sterman sees a convergence of many kinds of evidence. Singer says archaeology and ancient dyeing can’t override descriptions in Chazal that don’t fit the animal naturally.
R’ Yechiel Yitzchok Perr Weighs In
R’ Perr backed Singer’s conclusion in a letter to the editor and brought arguments of his own. He asked how the tiny quantity you get from a single Murex fits the Gemara’s discussion of the shiur for disha, why Chazal would call the Chilazon a dag when they had a perfectly good word for a snail, and whether potzea really has to mean cracking a hard shell.
He also pressed on whether the glandular secretion deserves the name “blood” in the sense the Gemara and Rishonim intend. Then came the historical argument, which is probably his strongest: the Mediterranean Murex industry stayed famous for centuries, so if this common and celebrated animal was the Chilazon, how did knowledge of it evaporate?
From Singer to Rav Shlomo Miller
Singer later put much of this history up on his Chilazon.com website, which works as a bridge between the first round and the second. The site presents his original article, Sterman’s response, his rejoinder and Perr’s letter as pieces of one debate. By early 2004 he was also circulating something new — a letter from Rav Shlomo Miller.
Late 2003–2004: Rav Miller Enters
Rav Miller’s letter was addressed to R’ Mendel Singer. He states that he’d gone to see where the Techeiles was being produced and came away unconvinced that the evidence proved the Murex dye was authentic. Two arguments he presents as especially strong.
1. Techeiles and Kala Ilan
He opens with the Gemara and Rambam’s tests. If Murex blue has been turned into material chemically identical to indigo, then no chemical test should be able to separate them, and for Rav Miller that isn’t a loose end waiting on better lab work. It’s an argument against identifying this material with the Techeiles Chazal describe.
2. The Shabbos Sugya
His second argument goes to Shabbos 75a and how the dye gets out of the animal. The Gemara deals with trapping the Chilazon, extracting the dye, and the dyer’s stake in keeping it alive because the dye comes out better that way.
Does the Murex process match that? Rav Miller asks why, if you’re cutting flesh or a gland out of a living animal, the sugya doesn’t run into netilas neshamah or gozez or some other melachah in the way you’d expect. He also notes that usable Murex dye material sticks around after the animal dies, while the Gemara seems to describe a genuine interest in keeping the thing alive.
Why Not Just Wear It as a Safek?
He takes on the nothing-to-lose argument too, citing a sevara attributed to R’ Chaim that fulfilling a doubtful mitzvah doesn’t discharge the obligation to seek a definite fulfillment. From there he raises the Rambam’s count of blue strings, possible bal tosif, the requirement that ordinary tzitzis match the garment when the blue is passul, and the Ben Ish Chai’s warning about kala ilan.
His conclusion goes past insufficient evidence. He writes that in his opinion there is a reason specifically not to use the new Murex Techeiles, and that sentence is what made the letter travel.
February 2004: The Letter Reopens Avodah
Singer posted it to Avodah on February 6, 2004, and the full discussion sits in the February 6–12, 2004 exchange. Singer summarized Rav Miller as holding that the Murex can’t be the Chilazon and that one should specifically not wear it, which was his own compression of the practical upshot; Rav Miller’s letter concludes that in his opinion there’s a reason not to use the new Techeiles made from Murex.
Bechhofer on Kala Ilan
Bechhofer went straight at the first argument and said he didn’t follow it. Why should chemical similarity between Murex blue and plant indigo make the Murex material into kala ilan halachically?
As he saw it, kala ilan is a counterfeit because of its source. Chazal weren’t sorting dyes by molecular structure, and two sources could produce the same color-bearing molecule while keeping entirely separate halachic identities.
That exposed an ambiguity already floating around since 2001. Was Rav Miller saying Murex blue literally is kala ilan, or that the chemical identity creates a contradiction with the Gemara’s ability to distinguish genuine Techeiles from it? Most of what followed dealt with the second version.
Ostroff Defends the Bedikah
Jonathan Ostroff answered by reducing everything to the test itself. Chazal describe a bedikah where real Techeiles passes and kala ilan fails; P’til had at points gestured at attempts to reconstruct it; and known plant indigo wasn’t behaving the way the sources require.
So you can’t run that experiment as evidence for Murex, Ostroff and Singer argued. A procedure that can’t flunk material already known to be kala ilan isn’t yet the test the Gemara is talking about.
Everyone agreed to that much. The split came at the next step. Singer and Ostroff treated the shared indigo chemistry as a substantial further problem — same principal blue substance in both, so what was the authentic test detecting? Berger accepted step one and rejected step two. A failed reconstruction indicts the reconstruction. It doesn’t show Murex failing the real test, and until Chazal’s procedure gets reproduced nobody knows what property it keyed on.
That distinction became one of the load-bearing points of the entire polemic: failing to reproduce the Gemara’s test is not the same as demonstrating experimentally that Murex fails the Gemara’s test.
Shabbos 75a: For or Against?
The same people then turned to Rav Miller’s second argument, and Bechhofer thought the sugya was actually one of the better arguments for Murex. You’ve got an animal with a shell that has to be opened and a dye-forming system that degrades after death, which looks like a decent fit for potzea and for the dyer wanting the Chilazon alive.
Ostroff read the same facts the other way. P’til’s own descriptions allowed usable dye material to remain for a while post-mortem, and if serious degradation only sets in after an hour or two, he questioned whether that explains the Gemara’s assumption that the dyer specifically wants it kept alive.
The factual ground was mostly shared. Murex dye chemistry deteriorates after death, nobody disputed that. What they disputed was whether deterioration on that timescale is what the Gemara is describing.
Moshe Sober from Toronto
Sober’s contribution is the kind of thing you don’t usually get in a written polemic. He wrote that while living in Israel he’d deliberately held off on Murex because the arguments in its favor struck him as almost too one-sided, and he wanted to hear a serious opposing case before changing his practice.
Then he moved to Toronto and learned that Rav Miller had investigated the matter personally, factory visit and all. Sober heard the objections secondhand at first, weighed them, concluded the pro-Murex case was still stronger, and started wearing Techeiles. When the actual written letter surfaced he said it was considerably stronger than the secondhand version and deserved careful study, though he still leaned toward the identification.
His account of how the disagreement functioned locally is the part worth preserving. He wore Murex openly in Toronto, including on occasion standing near Rav Miller in his kollel, and reported that neither Rav Miller nor his talmidim gave him grief over it. He also reported that Rabbi Kulik, a member of the kollel, had recorded a presentation working through both sides, challenging some of Rav Miller’s arguments and leaning toward the Murex while still recommending a conservative approach in practice.
Written polemics tend to leave a misleading impression of the atmosphere on the ground. Rav Miller’s conclusion was strong; the local reality, per Sober, was that people who disagreed wore what they wore and nobody made it personal. Sober also passed along a secondhand report about Rav Elyashiv’s private assessment, and since that’s hearsay rather than anything written, it’s best read as evidence of what was circulating at the time rather than as proof of Rav Elyashiv’s position.
Singer on Why Any of This Mattered
Bechhofer suggested at one point that people who don’t accept Murex could simply not wear it and leave the wearers alone. Singer rejected that framing. P’til was advocating a change in how a Torah mitzvah gets fulfilled in practice and marshaling historical and scientific claims to support it, and claims like that are fair game.
He separated the identification from the people, though. Singer said he’d personally helped interested people get hold of Murex Techeiles in earlier years and had respect for the ahavas hamitzvos driving many of the wearers. As the thread got sharper the tone itself became a topic, Singer clarified that his objections ran to arguments and to how they were being presented rather than to individuals, and the moderators eventually closed things down once it turned repetitive and hot.
What 2004 Added
Rav Miller’s objections came out of that exchange unresolved, but a lot more precise. On the chemistry, both sides basically agreed that modern attempts hadn’t reproduced the Gemara’s bedikah; the fight was over whether shared indigo chemistry counts as evidence against Murex on its own, or whether unknown source-dependent differences could still account for how the authentic test worked.
On Shabbos they agreed the dye system degrades after death and disagreed about whether the rate matches what the sugya needs. And on the practical question two opposite conceptions of safek sat side by side: Rav Miller and Singer read unresolved objections as grounds for leaving established practice alone, while Bechhofer and other Murex wearers read the chance of fulfilling a missing d’oraysa as grounds for uncertainty pushing toward wearing.
The scientific background behind the chemical objection, including the Toronto analysis later attached to Dr. Shabtai Nacson, comes below. What the Avodah material gives you is the arguments as they were actually being made in real time, before later accounts and later evidence got folded into the retelling.
The Testing Behind the Chemical Objection
During the February 2004 exchange Ostroff reported that a chemical engineer in Toronto had run P’til samples through analytical instrumentation. He wrote that someone had proposed residual brominated material as the distinguishing factor between Murex blue and plant indigo, and that the Toronto testing had come back identifying the dominant substance as indigo.
The engineer went unnamed in that post. Dr. Shabtai Nacson, known professionally as Dr. Sabatino Nacson, was later identified by his son Ariel as the scientist involved; Ariel also related that his father was close with Rav Miller and had a significant hand in the investigation behind the letter. A later unpublished draft by Ostroff preserves further correspondence about the experiments, according to which Rav Miller asked Nacson to examine samples from P’til and Dr. Sterman supplied three for testing.
What Nacson Found
He compared the P’til samples against commercial indigo, and his analysis pointed to indigo as the principal component of the Murex-dyed material. That result is real, and it’s also narrower than “the two are chemically identical.” Two dye preparations can share a dominant colorant while differing in minor compounds, brominated derivatives, residues and whatever else came along for the ride.
Nacson also attempted a simulation of the first test described by the Gemara and Rambam. Rather than reproducing the traditional mixture and letting it ferment, he used a modern reducing agent. Commercial indigo and the Murex sample both went from blue to a reduced yellow-green and both returned to blue on reoxidation, and Nacson read the Murex sample’s ready reduction as evidence against its being genuine Techeiles.
What It Didn’t Show
The full procedure of Chazal never got reproduced. Reduction and reoxidation are what indigoid vat dyes do, all of them, so showing that Murex blue undergoes that chemistry doesn’t tell you how dyed wool behaves in the specific mixture Chazal describe.
The traditional mixture wasn’t reproduced. The complementary barley-dough test isn’t documented. And the comparison ran against modern commercial indigo rather than plant indigo prepared and dyed by the historical fermentation method. A separate bleach experiment produced different behavior in the Murex and commercial samples, which complicates any claim that the two were chemically interchangeable to begin with.
So the experiment sharpened Singer and Ostroff’s question considerably: if both materials are dominated by the same indigo molecule and both reduce easily, what was Chazal’s test picking up on? It did not establish that Murex Techeiles fails the complete test the Gemara describes.
Rav Miller Answers R’ Zev Aryeh Knopfler
The letter wasn’t the end of it. Rav Miller later wrote a response to R’ Zev Aryeh Knopfler, who’d challenged parts of the argument, and the follow-up matters because it shows him defending the technical Shabbos material directly instead of restating his general opposition.
One of the issues there is what the Chilazon’s dam actually is. Rav Miller argues from how the Rishonim handle netilas neshamah and chovel that the dye material in the sugya has to carry the halachic character of life-related blood, and that the Murex glandular secretion doesn’t sit comfortably in that category.
R’ Eliyahu Tavger Responds
R’ Eliyahu Tavger wrote a direct response to Rav Miller, opening with an explicit reference to the letter Rav Miller had sent to Singer. His main chemical point is that you can’t collapse the question into “both are indigo.”
Murex dye can carry brominated compounds that plant indigo doesn’t have. Other accompanying substances, the preparation process, and the way the dye bonds to the wool could all plausibly affect the outcome of Chazal’s test. Identifying indigotin as the principal blue molecule doesn’t establish that two historically prepared dyes must behave the same under every chemical treatment, and demonstrating ordinary reduction and reoxidation doesn’t tell you what happens under the Gemara’s complete procedure.
On Shabbos
Tavger answers that cutting a large piece out of the animal isn’t the only way to get the secretion. The shell can be pierced or crushed, and ancient evidence describes more than one method of working Murex snails.
He also points to the Gemara discussing extraction from a Chilazon that had already died. Given that, the fact that Murex dye stays usable for a period post-mortem can’t disqualify the animal on its own.
R’ Yisroel Barkin’s Later Response
R’ Yisroel Barkin’s response belongs to a later stratum of the literature and wasn’t part of the 2004 exchange. He explains that he’d seen Rav Miller’s letter and afterward came across answers written by several talmidei chachamim, so his piece collects those and builds on them.
On “blood,” Barkin argues that dam here needn’t mean circulating red blood at all. Rabbeinu Tam’s description of the material as mifkad pakid, stored separately inside the animal, fits a specialized glandular substance well enough.
He also disputes the claim that safek Techeiles accomplishes nothing. People use safek tefillin and other doubtful mitzvah objects where certainty isn’t available, and a doubt hanging around doesn’t erase the possibility that the mitzvah is being fulfilled. Wearing the wrong number of blue strings isn’t automatically bal tosif either, while skipping genuine Techeiles means leaving out part of the mitzvah outright. As for the Ben Ish Chai, Barkin reads the warning as aimed at counterfeit kala ilan passed off as the real thing, rather than at someone honestly wearing Murex because he believes or seriously suspects it’s authentic.
Later Developments
A few things came along after 2004 that changed the evidence available. These should be held apart from what Singer, Sterman and Rav Miller had in front of them when they wrote.
Ancient Murex-Dyed Textiles
Later archaeological work turned up ancient textiles containing Murex-derived dyes, which strengthened the case that blue shades were being produced from the snail in antiquity. Whether any particular scrap of cloth was ritual Techeiles is a different question. A textile can establish the dye source and sometimes the color; its intended halachic use has to be established some other way.
The Raavya Manuscript
The most consequential later development touches Singer’s treatment of the Raavya. He was working from a printed text reading porphyrin and parufinen, and he tried to explain the second word through the Greek paryphainō, tied to weaving or furnishing a border, suggesting the passage might be describing a purple border rather than equating Techeiles with purpura. Given the text in front of him, that’s a reasonable thing to attempt.
Singer cited the Liddell–Scott–Jones Greek-English Lexicon by way of the Perseus database for the proposed sense of parufinen. In 2023 he was contacted and asked where exactly that definition could be found, and he replied that he’d used the Perseus site nearly twenty-five years earlier and no longer remembered how he’d searched it. He thought he’d printed the material out and said he’d try to locate it; nothing was produced in the exchange afterward.
None of that proves his reconstruction wrong. What it means is that the specific lexical basis for reading parufinen as a purple-bordered garment can’t be independently verified from the citation he gave. The bigger problem came later, when a manuscript reading was publicized showing the second word isn’t parufinen at all but prisinan, corresponding to Greek prasinon, leek-green.
The passage then falls into a clean parallel:
Techeiles — kartan
porphyrin — prisinan
Second pair, same color distinction as the first, with porphyrin lining up against Techeiles and prisinan against leek-green. You can’t fault Singer for lacking manuscript evidence that surfaced long after his article; he was making sense of the printed reading he had. With the corrected reading in hand, though, the paryphainō reconstruction isn’t needed anymore, and the Raavya turns into much better evidence connecting Techeiles to the purpura terminology.
What Was Actually Being Argued
Nobody was arguing about whether Murex snails figured in the ancient dye industry. They did, and all sides said so. Nor was the question whether a Murex can make blue, because it can. The fight was over what follows from those two facts.
Singer, Perr and Rav Miller give the descriptions in Chazal controlling weight. If the Murex doesn’t fit them naturally, then archaeology and chemistry documenting an ancient Murex industry can’t promote the animal into the Chilazon. Sterman, Tavger and Barkin fold the descriptions into a cumulative case where no individual siman is expected to do the identifying by itself, and the conclusion gets built from the Rishonim, ancient terminology, geography, archaeology, historical dye production and the chemistry of a working dye.
The AishDas threads expose a layer sitting underneath all of that. The participants were also arguing about what kind of evidence can restore a lost halachic identification in the first place. If an unbroken practical mesorah is indispensable, no quantity of shells or spectra restores Techeiles. If surviving textual identifications preserve enough of the mesorah for physical evidence to fill the gaps, the same shells and spectra become central.
The safek disagreement runs off the same divide. One side treats established white tzitzis as the known baseline that shouldn’t be disturbed without much heavier proof. The other asks whether continuing to omit what may well be genuine Techeiles is the riskier position to be standing in.
Which explains why identical evidence keeps sending the two camps in opposite directions. Chemical similarity between Murex blue and plant indigo is either a serious objection or exactly what a successful kala ilan substitute ought to look like. The vast purpura industry is either a famous purple trade with no bearing on Techeiles or the archaeological footprint of the industry that produced it. Post-mortem deterioration of the dye material either fails to match the urgency of the Shabbos sugya or corresponds to it strikingly.
Nacson’s experiment shows the same pattern in miniature. Singer and Ostroff read the shared indigo chemistry and the shared reduction behavior as telling against the identification, while their opponents answered that an incomplete modern simulation can’t determine how Chazal’s full test separated historically prepared dyes. The experiment established that the samples Nacson examined were principally indigo and that they reduced and reoxidized under modern chemical treatment. It didn’t establish that every constituent of Murex and plant indigo matched, and it didn’t reproduce the two-stage test.
One shell heap was never going to settle this, and neither was one molecule, one lab run or one line in the Gemara. Before anyone got to the evidence, the two sides had already disagreed about how evidence in a question like this is supposed to be weighed.
