PART THREE

THE MYSTERY OF THE TEKHELET

The Divine Blue

"Hashem spoke to Moshe saying: Speak to the Children of Israel and say to them that they shall make themselves tsitsi on the corners of their garments throughout their generations. And they shall place upon the tsitsit of each corner a thread of tekhelet... And you shall see it and remember all of the commandments of Hashem and you shall do them,"  (Bemidbar 15:37-39)

On History, Mesorah, and Nignaz, Mois Navon says “Archaeological evidence now available suggests that the origins of the purple and blue dye industry can be traced to Crete dating to 1750 BCE. And on a tablet from Tel el- Amarna, dating as far back as 1500 BCE, the phrase subatu sa takilti – a garment of tekhelet – is listed as one of the precious articles sent to Egypt by Dusratta, King of the Mittani, as dowry to the Egyptian prince who was about to marry his daughter. These finds, among others, indicate that mollusk based dyeing were in place long before the Jews came out of Egypt (1312 BCE) and that the dyes were used for royalty. So, just as the nations of the world used tekhelet to signify royalty, malchut, the Jews too were commanded to use it to signify malchut, malchut shamayim - the Kingship of Heaven.” Biblical Blue

"And the Rabbis said: Why does the Torah enjoin us regarding tekhelet? Because tekhelet resembles sapphire, and the Tablets were of sapphire, to tell you that so long as the people of Yisrael gaze upon this tekhelet they are reminded of that which is inscribed on the Tablets and they fulfill it, and so it is written, 'And you shall see it and remember.' (Mishnat Rabbi Eliezer, ch. 14).

One should always be heedful of the commandment to wear tsitsit, for the Torah equated and connected all other mitzvot with it, as it is written 'And you shall see it and remember all of the commandments of Hashem and you shall do them.'
(Rambam, Hil. Tsitsit, 3;13)

The Blue of the King of the Universe

The specific color referred to in “tecklet” can be identified by reference to the various scriptures. The Talmud in numerous places notes that tekhelet is similar to the sky or sea The Septuagint , the oldest translation of the Torah, renders tekhelet as iakinthos - blue. The Babylonian sage Saadia (born 882 CE) translates it as asma'ngon like the color of the clear sky, and Maimonides (born 1135) states, "it is the color of the clear sky visible near the sun."

"Rabbi Meir said: Whoever observes the mitzva of tsitsit, is considered as if he greeted the Divine Presence, for tekhelet resembles the sea, and the sea resembles the sky, and the sky resembles God's holy throne." (Sifre, Shelach, 15:39)

The Talmud (Sotah 17b) quotes Rabbi Meir as saying:

Why particularly Tekhelet [for the mitzvah of tzitzit] from among all other colored materials? Because Tekhelet is similar to the sea, and the sea is similar to the sky, and the sky is similar to the Holy Throne. As it says, "And they saw the G-d of Israel: under His feet there was the likeness of a pavement of sapphire, like the very sky for purity (Exodus 24:10)," and as it is written, "in appearance like sapphire stone was the semblance of a throne (Ezekiel 1:26)."

“Moshe and Aaron, Nadav and Avihu, and the seventy elders of Israel went up and saw the God of Israel. Under His feet was something like a pavement made of sapphire, clear as the sky itself.”

What they saw was Jesus in his human form – Yahweh the God of Israel with hands and feet!!

Saphire is blue in color and reflects the color of the sky.

“What makes techelet different from all the other colors, so that God commanded that it be added to the tzitzit? It is because techelet is like the [color of] grass, and grass is like the sea, and the sea is like the sky, and the sky is like the rainbow, and the rainbow is like the cloud, and the cloud is like the [Divine] Throne, and the Throne is like His Glory . . . and He granted [the mitzvah that includes] techelet to those that fear Him “. . . Bamidbar Rabbah 14

According to the Sefat Emet's mystical commentary, these three levels remind us of the Exodus (sea), the Torah (sky) and God's presence (throne).  . This was a colour worn by the priests, so wearing a blue thread would remind us that we are a holy people. According to the midrash, the blue reminds us of the tablets (which were inscribed on sapphire)

The Techelet (or Biblical Blue) dye is mentioned throughout the Old Testament, together with another similar dye named Argaman (Royal, or Tyrian, Purple) which were used by the royalty all over the world. 

Techelet and Argaman were part of the priestly garments of Kohanim as they served in the Holy Temple. The inclusion of the Techlet as part of the daily wear of every Children of Israel indicated that  "All the Bnai Yisroel are like sons of kings" (Shabbat 111a).     

The Midrash says:  “The Techelet reminds us of the dominion of Hashem Himself. It is attached to our garments to show all that we are none other than His own children! “(Socher Tov Tehillim 90, "V'Hadarcha Al B'neihem").

The ancient land of Canaan and its corresponding Greek name, Phoenicia, mean "the Land of Purple" (Astour, Michael C. "The Origin of the Terms 'Canaan,' 'Phoenician,' and 'Purple.'" Journal of Near Eastern Studies 24, no. 1 (1965): 346-350.).   It was into this land of Purple royalty, the Children of God were led into and was asked to take possession.

In keeping with this tradition, the Christians in Malabar Coast are still called – as they used to be called from the first century AD – as Mapillai short for Maha Pillai – the Children of the Great King. The first Christian Church was established by Thomas the Apostle was among the Jews of the Malabar in Ad 52.  Most Syrian Christians still have the Kohanim DNA. As their ancestor heritage.

The following is a list of items incorporating Tekhelet, as recorded in Exodus and Numbers:

·         Loops on coverings of the Tabernacle (Lulaot ). The coverings of the Tabernacle (Mishkan) were prepared from panels of animal hides, attached to one another with metal (gold, copper) hooks. On the edges of each panel, there were 50 loops (lulaot) made from Tekhelet threads. The 50 loops of one panel were aligned and adjoined with the 50 loops of the adjacent panel via the metal hooks.

·         The Screen for the Courtyard Gate (Masach L'Shaar HaChatze)r of the Tabernacle  was made from all the fine textiles, including Tekhelet. It was hung upon 4 posts of silver-plated pillars of wood having silver hooks, and set in 4 copper sockets.

·         The Partition (Parochet) which separated the Holy  from the Holy of Holies was made from all the fine textiles, including Tekhelet. It was hung upon 4 posts of gold-plated pillars of wood having golden hooks, and set in 4 silver sockets.

·         The screen in front of the Tabernacle (Masach L'Petach HaOhel ) was made from all the fine textiles, including Tekhelet. It was hung upon 5 posts of gold-plated pillars of wood having golden hooks, and set in 5 copper sockets

·         The Apron (Ephod) One of the 8 garments of the High Priest (Kohen HaGado)l, the apron was made from all the fine textiles, including Tekhelet. Two precious stones, set in gold, were engraved with the 12 names of the tribes and inlaid on the shoulder pieces of the garment.  Ex. 28:6-14, 39:2-7

·         The Rob (M'eel HaEphod)  One of the 8 garments of the High Priest, was made entirely from Tekhelet, with extra decorations. On its hem were golden bells alternating with pomegranites made from Tekhelet, argamman, and crimson. Exod 28:31-35

·         The Tassel (Tzitz)  One of the 8 garments of the High Priest,  was made from gold and engraved with the words “Holy to the Lord” ("Kodesh LaHashem"). It was tied on with a Tekhelet cord, and lay on top of the headdress. Exod 28:36-38

·         The Sash (Avnet)  One of the garments of the Priests, was made from fine linen embroidered with Tekhelet, and argamman and crimson.

·         Bigdei HaSrad When travelling, the various items inside the Mishkan were covered with cloths (bigadim) and transported on poles. The coverings were as follows:

·         The Ark containing the Tablets was covered with the parochet, then skins, then a Tekhelet cloth.

·         The Showbread Table was covered with a Tekhelet cloth, upon which were placed the bowls, ladles, jars and jugs and bread. On top of this was placed a crimson cloth.

·         The Menorah, as well as its lamps, tongs, fire pans and oil vessels were covered with a Tekhelet cloth and then skins.

·         The Incense Altar (golden) was covered with a Tekhelet cloth and then skins.

·         All the service vessels were placed in a Tekhelet cloth and covered with skins.

Only the Sacrifice Altar (copper) was not covered with Tekhelet, but rather with a purple cloth, upon which were placed all its accessories, and then a covering of skins.

Evidently what is portrayed here is the Majesty of the King of Kings and the Lord of the Universe through the Divine Blue- the Techlet.

Techlet lost

When the Romans  conquered Israel in 63 BC they  seized control of the industry of this royal blue product.  Romans (Constantius 337-362) went to the extent of strictly prohibiting its use except for ritual use.  Only the Royal descendants were allowed to wear the Blue.   As a result  Jewish dyers went  underground.   (Even  During the reign of Queen Elizabeth I, purple-hued clothing was a luxury permitted only to "Dukes, Marquesses, Erles, their children or Barons and knights of the order" )

As children of the King, throughout the times of the Mishnah and the Talmud the Israelites used Techelet string in the Tzitziot.  Even after the dispersion of Israel the oral tradition was carried over by Jewish scholars known as Amora’im (which simply means “those who tell over”).  From 200 -500 AD these scholars in Babylon in their land of disperson codified the oral tradition as Gemara.  The Amoraim followed the Tannaim of earlier scholars.   The Tannaim were direct transmitters of uncodified oral tradition; the Amoraim expounded upon and clarified the oral law after its initial codification.  In these distant lands where Techlet was difficult to get they were still worn by the Amoraim. (Menachot  43a Sanhedrin 12a). “Gemara (c. 550-570) contains numerous references to the ritual use of tekhelet; the latest of which tells of tekhelet being brought from Israel to Babylon in the days of R. Ahai (506).”  This is the last historical evidence of its existence. 

By 639 CE at the time of the Arab conquest, the secret of Techelet was lost all together.  Midrashim (Bemidbar Rabba 17:5; Tanchuma, end of Sh'lach) says that the “Techelet has been "hidden away" ("Nignaz")”.   

In “Understanding the Criteria for the Chilazon”  Mendel E. Singer suggests that the dye was produced in secret for another several hundred years or so,  before it was lost.  At any rate it was beyond the means of ordinary Jew. 

As the Jews were exiled and were scattered all over the world  the identity of the creature  that produced the dye and the dye-processing techniques were eventually lost. These were evidently trade secrets of a few.  Thus Israel could not keep the mitzovot.   

"And now we have only white, for the tekhelet has been hidden."
(Bemidbar Raba 17:5) 

As a result some people began to wear alternate blue colors from plants. The strictly legalistic character of the Jewish scholarship this was not Kosher. 

“Techelet is only kosher if it is made from the Chilazon; if it is not made from the Chilazon it is invalid.” (Tosefta Menachot 9:6, Beraita in Massechet Tzitzit 1:10)

It would then mean not wearing the Tzitzit?

The requirement of the blue thread mitzvah was reinterpreted as two independent parts without correlation. 

The two rules now are:
1. wear techlet string on the tzitzit,
2. wear tzitzit,

So if we cannot wear blue thread, it is Ok to wear tzitzit without it.  You are still keeping one mitzvah which you can. For about 1500 years, Jews have only worn white tzitzit. 

They used white because God’s tallit is white. Any blue tekhelet that is not hillazon based is to be considered as  kela ilan (alternative dye) and Gemara (B. Metz. 61b) warns of divine punishment for wearing kela ilan. (False Tekhelet, Mois Navon, 5764)

But every Jew knew that “The essence (ikar) of the mitzvah is tekhelet and one wearing white without tekhelet has not fulfilled a complete mitzvah” (mitzvah shleimah).  Rashi on Men. 40a

There was a new zeal to determine the origin of techlet and reinstitute the full mitzvoth.

"There is an obligation, upon all who are capable, to search for it [the Chilazon], in order to bring merit upon Israel with this commandment, which has been forgotten for the last several centuries. And he who succeeds in this will surely be blessed by the God of Israel." (Rabbi Gershon Henoch Leiner, the Radzyner Rebbe)

So the seach began.

The loss of the Divine blue is attributed to the disobedience of Israel as part of the destruction of the Temple.   It has been suggested that the blue will be discovered an reinstated before the coming of Mesiah in His glory to Israel.  With the return of the Jews to Jerusalem and the renewed hope of rebuilding the temple and re-establishing the priestly worship created a new search to discover the lost teklet color.

Techlet regained

The Chilazon

According to the oral traditions, the blue dye was obtained from an animal called Chilazon.  The word (chilazon) does not appear in the Torah at all.  The source of the blue color as coming from chilazone is only from the Oral Traditions.

The  oral tradition of Talmud Menachot 44a states  that
“The Chillazon is this: its body is like the sea, its creation is like fish, it comes up once in seventy years and with its blood one dyes tekhelet - consequently it is expensive”. (Menachot 44a) 

Chilazon in modern Hebrew means "snail".

So we know that chilazon

• Has something to do with the sea and blue in color
• It comes from a sea creature resembling fish
• It appears only once in 70 years.
• The dye is made from the blood of the animal.
• The blue is very expensive

Since it is expensive only one blue thread is required of in the tzitzit.

Other criteria from tradition include:

• The fishers of the chilazon are from Haifa to Tyre (Shabbat 26a)
• The color of the chilazon dye is identical to that produced from the dye of the kela ilan plant (Indigofera tinctoria), which served as a counterfeit source of the dye (Baba Metzia 61b)
• Cracking open the shell of the chilazon on Shabbat violates the laws of Shabbat (Shabbat 75a)
• The shell of the chilazon grows together with it (Midrash Shir haShirim Rabbah 4:11)
• The chilazon buries itself in the sand (Megila 6a)
• It is an invertebrate (Yerushalmi Sabbath 1:3 8a)

Karaite Tzitzit, using a generic blue dye

According to the Talmud, tekhelet () appears 48 times in the Tanach. This is translated by the Septuagint as "iakinthos" (blue). This is a specific dye of blue produced from a creature referred to as a "chillazon" impying that no other blue dyes are acceptable (Tosefta).

The Talmud recounts that the Chilazone appears only once in seventy years (Menachot 44a).

Chilazon: Its dye is used for the Techelet Dye for Tzitzit-Fringes: Menachot 44a

A description of its appearance: Menachot 44a

It is only found once in 70 years: Menachot 44a

The Chilazon was found in Zevulun's portion in Israel: Megillah  6a

Grand Rabbi Gershon Henoch Leiner and the cuttle fish

The first concerted scientific effort in identifying Chilazone was done by Grand Rabbi Gershon Henoch Leiner, the Radziner Rebbe,  (1887 AD) who concluded that the Sepia officinalis (common cuttlefish – ink fish) met many of the criteria. It hides in sand and has blue blood, unlike regular fish. (The blue color  of the  blood is because it is  copper-based, unlike the vertebra's red blood, which contains hemoglobin and is iron-based.) Within an year, Radziner chassidim began wearing tzitzit dyed with a colorant produced from this cephalopod. The Breslov Hasidim also adopted this custom (Breslov  is a branch of Hasidic Judaism – A Piety Movement - founded by Rebbe Nachman of Breslov (1772 – 1810) a great-grandson of the Baal Shem Tov, founder of Hasidism.)

"The [squid] blood ... is mixed with iron filings and a snow white chemical called potash. After keeping it on a large powerful fire for some four or five hours, until the flames burn outside and inside as the fires of Gehenna, the mixture fuses..." (from a letter sent by the Radzyner dye master to Rabbi Herzog)

The color of the Radzyner Tekhelet is very deep dark blue. When   The production of Tekhelet continued for more than 100 years. But the details of the procedure developed by the Rebbe  were lost during the Holocaust.

Rabbi Issac Herzog and the  Janthina

Rabbi Yitzhak HaLevi Herzog (1889–1959), also known as Isaac Herzog, was the first Chief Rabbi of Ireland from 1921 to 1936. From 1937-1959  he was Ashkenazi Chief Rabbi of the British Mandate of Palestine and of Israel after its independence in 1948. His son Chaim Herzog became the President of Israel later. Rabbi Herzog rejected the Radzyner Rebbe's position, and concluded that the chilazon was a member of the Janthina species.[ Rabbi Isaac Herzog, "Hebrew Porphyrology".]

 However, the dye produced by the Janthina turned brown, and was not permanent. It appears that Rabbi Herzog did not pursue this matter further, and no techeilet was ever produced from the Janthina.

Rabbi Yitzhak HaLevi Herzog   in his doctoral thesis in 1913 he proposed that  Murex trunculusas was the most likely candidate for the dye's source.

Dr. Israel Irving HaCohen Zinderman and  Murex trunculus

Following Dr. Irving Ziderman, an academic scientist at the Israel Fiber Institute, followers of this theory formed an organization, Petil Tekhelet Foundation.

According to Shir HaShirim Rabba (4:11), a Chilazon is a creature that lives inside a shell and according to Bechorot (Mishna 6:2) and in Kelim (12:1) it is something with a spiral or twisted appearance and is dubbed "Chilazon."  Sanhedrin 91a Chilazons appear on the ground after a rain.

According to this new studies theory  murex trunculus was the chilazon.

The Murex trunculus dried and Tekhelet thread from it

A coin from the city of Tyre dated 200 C.E. depicts the legend of Hercules' dog discovering the Murex

However there are problems in positively identifying the Murex as the Chilazon

1.  The dye from the trunculus is purplish-blue, not pure blue as tradition maintained. However if it is exposed to strong sunlight it turns blue.

2.  The color of the snail is off-white shell with stripes of brown and not similar to the sea.

3. Murex trunculus in no way resembles a fish.

4.  The snail itself is a sea creature which has no fins nor scales which becomes an abomination to the Mosaic rules.

Rabbenu Bachye  insists that according to the Gemara Shabbat 28b the only products which are kosher to be eaten were used in the Mishkan. Chilazon, which is a sea creature, must be a fish, with fins and scales.

But most others do not insist on this.  The idea is that  we can use a non-kosher creature in the process of manufacture of an item used in the Tabernacle,  The actural  material itself should be Kosher.  An example of this is given in Talmud Yerushalmi (Kilayim 9:1), where  the scarlet dye of Tola'at Shani (crimson used in Priests garment)  was indeed extracted from a worm (the female Kermococcus vermilis, an insect that breeds on a certain species of oak).

The Chemistry of Tekhelet

Dyes that are used must have the property of not running in water as the clothes are washed.  In order to have this property, the dyes must be insoluble in water.  In that case it cannot be used directly on the clothes as a water solution.  The solution to this problem is to use a form reduced form of dye which is soluble in water  which is then used in  a vat to dye.     The process of dyeing is then done  in a Vat. (“Yora” in Hebrew)  to absorb the reduced dye on to the thread.  The clothe is then  taken out to dry in the air. The oxygen recombination transforms the dye back to its insoluble colored form.   This then is a permanent dye.  The chemical processing of indigo blue is shown below.  Here indigo is reduced to leuco-base form which is yellow that is soluble in water.  Once the clothe is dyed with this yellow dye, it is hung in the air.  Under the action of light, heat and air it oxidizes back to  blue.

Tekhelet Blue - Dye Bromo Indigo

Dye Bromo Indigo is the main colorant in the Tekhelet.  It contains 3 Atoms. When the Dye is exposed to the Sun, Bromine Atoms are broken between the Indigo Atom and the two Bromine Atoms leaving the Indigo which is mostly Blue.

Vat dyeing process. Indigo is insoluble in water but leuco-base is soluble in alkaline water.  “Leucos” means white.

Inside the hypobranchial gland of the snail, the precursors to the dye exist as a clear liquid. When these are exposed to air and sunlight in the presence of the enzyme purpurase, which also exists within the gland, they turn into the dye. Purpurase quickly decomposes, so for this reaction to take place, the gland must be crushed soon after being taken from the live snail, in accordance with the Talmudic passage that the tekhelet is taken from the Chilazon while still alive. The liquid from the trunculus, produces a mixture of dibromoindigo (purple) and indigo. These molecules must be put into solution for them to bind tightly to wool. In this state, if dibromoindigo is exposed to ultraviolet light, it will transform to indigo, turning the trunculus mixture from purplish-blue to pure blue.

The tekhelet molecule (indigotin) gets its color from a strong absorption peak centered at 650 nm and also at around 300 nm

. (nm stands for nanometer; which is a unit of length in the metric system, equal to one billionth of a metre (i.e., 10^-9 m or one millionth of a millimetre).  Wouters and A. Verhecken studied the characteristics of the different dye molecules obtained from the Murex trunculus snail.  The above graph gives the absorption of the dye as a function of the wavelength expressed in in nano meters.  The visible blue light has a wavelength of about 475 nm. Because the blue wavelengths are shorter in the visible spectrum, they are scattered more efficiently by the molecules in the atmosphere. This causes the sky to appear blue.  There is an absorption maximum at around 613 nm which actually corresponds to the orange color wavelength.  The minimum absorption actually take place from 400 500 nm range which produces the color of the pigment as these are predominant in the reflected light.

P'til Tekhelet
The Association for the Promotion  and Distribution of Tekhelet  Jerusalem, Israel

These are the arguments presented by the P”til Tekhelet.

1) The Talmud, regarding tzayadei chilazon states the following: Murex brandaris, a sister species to Murex trunculus, will also fill all the specifications laid out in this monograph. The contention is that the chilazon is identified with both of the two murex species since each of these has brominated indigo as natural chemical in its mucus, from which the murex- derived indigo can be extracted. 

 Shabbat 26a ..these are the fishers of chilazon from Haifa to Sidon From this statement we can derive that the natural habitat of chilazon was off the shores of what is today northern Israel and southern Lebanon, and what was, in ancient times, Phoenicia.

2) It is documented that the center of the dye industry in the ancient world was Phoenicia.  The most famous of the dyes was Tyrian Purple, an extremely expensive dye that was in great demand by the nobility and the extremely wealthy, as it was unique in its beauty and color-fastness.

3) If one opens a Murex trunculus snail and squeezes the hypobrachial gland one will obtain a clear mucus. This mucus, if taken out of the shell and exposed to the air, will change from its clear color to yellow, then to green, then to blue and finally to purple.

4) In the late 19th and early 20th century, there were archeological findings of enormous numbers of broken Murex shells discovered near the cities of Holy Land.

Biblical city of Dor where recent archeological excavations served as the initial impetus for the rediscovery of techelet. Located on the Mediterranean coast near Caesarea, Dor is mentioned in the books of Joshua, Judges and Kings and was the main port city in this area until Herod built nearby Caesarea in the late first-century B.C.E. In Dor, archeologists have discovered evidence of a dyeing industry dating back to the Roman period. Specifically, they uncovered large dyeing pits with rings of purple (argaman) and blue. The discovery of large numbers of broken shells of Murex snails around the vats led experts to the conclusion that this snail, which is found in nearby coves along the shore, is indeed the chilazon of our tradition.

When the land of Canaan was occupied by  Israel,  Dor  was  allotted to the tribe of Asher (Jos., xvii, 11), then given to Manasseh (Judges, i, 27), who failed to expel the inhabitants of the land and take possession of it.  The Egyptian Pharoah Rameses III set up a Phoenician colony at Dora; according to Stephan of Byzantium the Phoenicians settled there because the coast abounded in the shells that produced the famous Tyrian purple dye.

Recent excavation at the site has revealed one of the largest murex dye industrial complexes ever found along the Levantine coast.  In Dor, archeologists have discovered dyeing pits with rings of purple (argaman) and blue which date back to the Roman period.  Shells of Murex snails were found scattered all around these pits suggesting that these are the resources from which the blue and purple dyes are made and are the hilazon of Hebrew tradition.

Dyeing Pit found in Dor

• The Jerusalem Talmud (as quoted by the Raavyah) translates tekhelet as porphiron (the Latin and Greek name for trunculus-like shells). Pliny and Aristotle describe these shells as the source of the ancient dyes.
• The Talmud indicates that true tekhelet is indistinguishable from the blue dye of vegetable origin - kala ilan (indigo). The dye ultimately derived from trunculus is molecularly equivalent to indigo.
• Extensive marine biological surveys have revealed that the only snails in the Mediterranean which produce stable dyes are those of the Murex family. The dye obtained from trunculus is very stable and steadfast, which accords with the Rabbinical description of tekhelet.
• Archeologists in Tyre and elsewhere uncovered mounds of Murex shells dating from the Biblical period which were broken in the exact spot necessary to obtain the dyestuff. Chemical analysis of blue stains on vats from 1200 BCE reveals patterns consistent with those of modern day trunculus.

When listing the precious commodities used in building the Mishkan (tabernacle), the Torah consistently includes tekhelet along with gold, silver, and other familiar materials, recognized by all for their worth. Yechezkel speaks of the tekhelet from Tyre and the "Isles of Elisha", and the Megillah tells us that in Persia, Mordechai wears royal clothes made of tekhelet. Surely, the Torah is referring to that same valuable dye commonly used by royalty throughout the rest of the ancient world.

 Shard of a vat found at Tel Shikmona from the Bronze Age, 3200 years old. The chemical composition of the stain is identical to the dye obtained from Murex trunculus.

P'til Tekhelet
The Association for the Promotion  and Distribution of Tekhelet  Jerusalem, Israel gives the following table for the
Criteria for Identification of Tekhele &  the Hillazon
Prepared by Mois A. Navon

The ancient process is given by Pliny the Elder:

 “There is a white vein with a very small amount of liquid in it; from it is obtained that well-known dye which shines faintly with a deep rosy colour, but the rest of the body is unproductive.

[...] Men try to catch the murex alive because it discharges its juice when it dies. They obtain the juice from the larger purple-fish by removing the shell; they crush the smaller ones together with their shell, which is the only way to make them yield their juice.

[...] The vein already mentioned in removed, and to this, salt has to be added in the proportion of about one pint for every 100 pounds. It should be left to dissolve for three days, since, the fresher the salt, the stronger it is. The mixture is then heated in a lead pot, with about seven gallons of water to every fifty pounds, and kept at a moderate temperature by a pipe connected to a furnace some distance away. This skims off the flesh which will have adhered to the veins, and after about nine days the cauldron is filtered and a washed fleece is dipped by way of a trial. Then the dyers heat the liquid until they feel confident of the result. A red colour is inferior to black.”   (Pliny the Elder, Natural History, first century BCE)