This blog post from Ben's Tallit Shop made me start looking for a source:

Let me warn you that the Radzyn techelet dye runs. Your hands will turn blue, your tallit may get a bit smudged and the white tzitzits will get slightly discolored. From my experience the smudges come out with a damp cloth. The proponents claim this is a sign that the Radzyn dye is authentic, citing an early source that techelet was known to run.

(Emphasis mine)

What is the "early source" he might be talking about? Is it true that tekhelet was known to run?

  • does this begedivri.com/techelet/Sefunei.htm help? Commented Aug 24, 2016 at 21:35
  • @AvrohomYitzchok, begedivri.com is a Judaizing Christian site, not a Jewish site. Commented Sep 8, 2016 at 12:39
  • @NoachMiFrankfurt Thank you. It's certainly interesting. How do you know that it is not a Jewish site? Commented Sep 8, 2016 at 15:11
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    @AvrohomYitzchok, "Beged Ivri is the Levitical Ministry, established in 1983, for the research and restoration of ancient Israelite customs in preparation for rebuilding the Holy Third Temple in Jerusalem." Pretty Christian sounding to me. Commented Sep 8, 2016 at 15:14
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    IIRC, Rambam understands that only kala ilan runs, not techeiles, and uses that to differentiate between them. Commented Feb 22, 2019 at 21:38

1 Answer 1


I don't know if this is precisely what is meant by "running", but the Radziner Rebbe mentions that techeiles is supposed to be able to be washed out with soap, and the dye can also fade due to other factors (e.g. exposure to sunlight). The Radziner Rebbe cites the last Tosafos in Zevachim 95a as a source, as Tosafos there says that the dye in the High Priest's robe could be washed out with soap:

אבל מעיל דכהן גדול אינו יכול לכבסו ע"י צפון משום דאמרינן במסכת נדה דאפילו צבעא נמי מעבר

The Radziner Rebbe discusses this in Pesil Techeiles #1, Pesil Techeiles #4, and Ein Hatecheiles 1:31 and 1:32.

  • As with any dye, they all wash out at the beginning of the dying process. Even those known as color fast. The setting of the color is how the dye molecules bind to the fibers. But after dying, setting and washing is necessary. For colorfast dyes, after final washing, a residual level of the color binds with the fiber. It is 'more permanent'. But even with that, depending upon the type of 'soap', even colorfast dye will wash out. Commented Feb 22, 2019 at 17:52
  • Yes that is what is meant by running I believe
    – ezra
    Commented Feb 22, 2019 at 21:13

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