Over the past few months I have received several inquiries about whether the dye used to make techelet tzitzit has to be made from a kosher animal. For instance, just yesterday I received the following inquiry from someone in eastern Washington state who has been looking into various tzitzit and techelet topics:
In my research on tallit and tzitzit, I have noticed that there are at least two historical sources for the indigo dye: cuttlefish and the Murex trunculus snail. Also, I have seen that plant sources for the indigo dye are not acceptable for dyeing the blue cord of the tzizit. My question is this: If plants are considered kosher, and snails and cuttlefish are considered to be treif (no fins or scales), how is it that no plant-based dye can be used on the tzizit?
The Gemara discusses a concept referred to as mutar b’ficha, which means literally permitted to put in your mouth, i.e. kosher. This applies to tefillin, mezuzahs and Sifrei Torah, and the Magen Avraham concludes that this rule applies to all other mitzvahs as well. But upon further examination it appears that mutar b’ficha applies to all tashmishei kedushah (holy mitzvah objects) with the exception of dyes.
For an in-depth examination of this question, see The Hillazon and the Principle of Muttar be-Fikha by Rabbi Mois Navon of the Ptil Tekhelet Association. It was originally published in the Torah u-Madda Journal in 2001 and is available in PDF form here: www.tekhelet.com/pdf/Mutar_Beficha.pdf