When it comes to the raging debate over whether Murex trunculus is the real techelet mentioned in the Torah, it’s hard to find someone who is really objective on the issue. Many people, including some rabbanim, seem to have made up their minds for the most part, before they start “investigating” the matter.
For example, a year or two ago a Torah scholar in Bnei Brak published a booklet strongly arguing against Murex trunculus as the real techelet. While reading through it, I felt it was very clear the writer was extremely biased and presented his case in a highy selective manner. When discussing the correct color of techelet, for instance, he wrote that according to Rashi it should be a very dark blue, almost black, but neglected to mention the many opinions – including Rashi himself, elsewhere – that speak of very different shades of blue (see below). In the booklet he also claimed the chilazon is found in the Kinneret. This opinion is mentioned in the Midrash, if I’m not mistaken, but a much more accepted opinion is that the chilazon dwells in the Mediterranean.
That’s why it helps to take a look at what Rabbi Aryeh Kaplan zt”l wrote over 30 years ago in his commentary on Chumash, The Living Torah. And it’s particularly worth taking a look now, since you will find it in this week’s Torah reading, Parshas Terumah.
The verse in Shemos 25:3 lists the various materials used in the construction of the Mishkan, including techelet. Rabbi Aryeh Kaplan translates it as “sky-blue.” The shade of techelet is a matter of debate in and of itself, and Rabbi Aryeh Kaplan mentions five or six different opinions, including Rabbi Saadia Gaon, Rambam, Yosephus, Rashi and Radak.
Sometimes I get customers who ask for me to dig through my stock of Ptil Tekhelet for the darkest set I can find (or sometimes the lightest). Although there can be slight differentiation between one batch and another, for the most part they all look to me to be the same shade. However, the thin is always noticeably darker than the thick, presumably because the Murex trunculus dye penetrates better.
Rabbi Kaplan goes on to mention various points that anyone who has looked into the present-day techelet debate will recognize immediately: purpura, Murex trunculus shells found at the site of the ancient Tyrian dyeworks and the signs of the chilazon.