Shalom, I have taken quite a while between posts…..too long.
One of my long-term research/application topics is the studying of “techelet,” the color of tzitziyot (“tzitzits”). Usually translated as “blue” in most English translations, but translations vary from violet (the New Jerusalem Bible) to turquoise (Artscroll Stone Edition Tanach). One significant question is: “What made the blue/violet/turquoise dye when Israel left Egypt?” The rabbinic view is that the term “techelet” refers as much to the source of the dye, rather than the specific color itself. The Karaite view dismisses this question (“blue is blue, and so whatever makes ‘blue’ is fine) but it doesn’t even attempt to answer it.
The Talmud tells us that the dye came from the “chilazon,” but does not provide a detailed description of what exactly this dye source really was. Later rabbis like RaMBaM (Maimonides) only describe its properties. The leading contenders today are the cuttlefish (kind of squidlike) and the murex trunchular sea snail (also referred to as a mollusk). The Temple Institute favors the murex snail, and have used this dye for “techelet” items to be used in the next Temple. Recently, there was an article about the recent analysis of a small piece of fabric (discovered in the 1950s) at a cave in which Jewish fighters aligned with Shimon bar Kochba were said to have hidden. The fragment, found at Wadi Murba’at, was analyzed by Dr. Na’ama Sukenik, of the Israel Antiquities Authority and determined to have been dyed from the murex trunchular.
“To this day, scientists and scholars have not reached a consensus on whether tekhelet was a light sky-blue color, as most modern day experts on the subject now believe, or a darker, more purple-hued blue. The shade discovered on the piece of fabric tested by Sukenik was sky blue. The tassels on the fragment were spun in a way that was common in Israel in ancient times, she said, demonstrating that the dye was locally produced.” (Ha’aretz, 30 Dec 2013).
The article stated that this was only the third time that fabric had been discovered linked to the murex. Baruch Sterman, co-founder of the Ptil Tekhelet Association, a non-profit organization that produces tzitzit dyed from the murex snail, said that there was no evidence “that other two pieces of fabric containing the blue dye derived from the murex were produced in ancient Israel.” The article continues: “One fragment, containing a light blue color, was discovered in the Pazyrik region of Russia, and the other, containing a darker blue, was discovered during the Masada excavations. The fragment discovered in Masada, he said, may not necessarily have been produced locally.”
“Not produced locally” would seem to indicate (in Masada’s case, at least) that the fabric containing murex dye was Roman. We see, for example, that murex snails were most famously used for dyes from the Imperial Roman period: http://archaeology.about.com/od/rterms/g/royal_purple.htm
Clearly, this is an ancient practice. Of course, the fact that Romans famously used snail dyes says nothing about whether they were used by Israel for tzitzit.
We do have an example of a seller of “purple” fabrics from the Ketuvim Netzarim (Nazarene Writings, aka the New Testament). In Acts 16:14 we see Lydia, a seller of “purple.” The word used is “argona” in the Aramaic Peshitta text, a cognate to the Hebrew “argamon.”
Two plant dyes are also possible: indigo and woad. I found a passage in the Mishnah that said the priest is not to raise his hands to pray if his hands were stained with woad as the people would be looking at his hands and not praying properly.
• “A PRIEST WHOSE HANDS …..ARE DISCOLOURED WITH WOAD SHOULD NOT LIFT UP HIS HANDS [TO SAY THE AHARONIC BLESSING], BECAUSE [THIS MAKES] THE CONGREGATION LOOK AT HIM.” Mishnah, Megillah 4:7

What business does a priest have in dying with woad unless it is for the purpose of the Temple or Tabernacle? We know, therefore, that there would not be a prohibition against having woad dyed hands……unless priests were using woad and showing up to say “Y’varekh’kha….” with woad-stained hands. What they used it for is not stated, but it could not be for a common purpose – they were sons of Aharon!
So, these sons of Aharon are about the Eternal One’s business, and if what they are dyeing is for the Temple or Tabernacle, the only “blue” mentioned is “techelelet” and that is the color for tzitziyot (tzitzits) as well as Temple/ Tabernacle furnishings (remember “blue, purple and scarlet”?). Thus, the dye extracted from the woad plant would be the true techelet (not a squid-like cuttlefish or a sea snail).
Woad is a plant grown from Egypt to England in the ancient world as a dye plant. Pyramids/Mummies have woad residue, so we know it is very ancient. It appears that a woad and madder root dye was used to dye spools of thread in Simon bar Kochba’s army, but whether it was used to make tzitzits is not certain. Indigo probably wasn’t imported into Egypt (from India) until much later. Since Israel was in the wilderness (with a lack of cuttlefish and sea snails) and surely knew of woad from Egyptian days, it seems to me most likely that woad was the source of techelet to Israel. The cuttlefish and snails are not clean animals, but the question is whether this is a true requirement or not. However, a plant-based dye vs. an unclean animal does have a certain appeal.
The “history factor” should be a prime consideration, as the command to wear tzitziyot was given in the Wilderness. Whatever was used to make tzitziyot must have been available in the Wilderness or was brought with the Children of Israel out of Egypt. This seems to rule out the famous snail dyeing establishments in Tyre. Cuttlefish are known to inhabit the temperate coastal waters of Africa and the Mediterranean, so it is technically a possibility. And yet, when Israel crossed Yam Suf fleeing Pharoah’s army, there does not seem like time was available to collect cuttlefish. Adding to that, the mitzvah to wear tzitziyot was given after the Children of Israel were near the coast. Were they carrying cuttlefish with them? H’mmmm…..
The oral tradition says that real techelet is exactly the same color as indigo, but indigo is not techelet. I’ve found that the common denominator of the “blue” in the snails, in indigo, and in woad is “indigotin” (in-DIG-uhtin). They all have it, and that is what gives the color. Woad gives a natural dye color similar to indigo, of course, and as I’ve been able to get a deep blue dye – much deeper than either the tzitzits I’ve purchased from Israel using either snail dye or cuttlefish die – if something gives the same color of blue as indigo, and yet it is “not indigo” it seems to me that woad is a viable choice for tzitziyot (particularly given the fact that in Temple times we know from the Mishnah that the priests definitely used woad).
I have been dyeing tzitizits with woad for several months now, and depending on how the wool thread is prepared prior to dipping into the dye vat and how many times you dip it….I have colors varying from a deep midnight blue to a near turquoise color. This was somewhat surprising since many reports say that woad gives a very pale blue.

For further reading I recommend:  http://curtisdward.wordpress.com/2011/01/05/what-is-the-true-tekhelet/

I hope to have woad tzitzits up on this site for sale in the very near future, along with tying instructions for those that have not tied their own tzitzits before.