>We had a thread on shell dyes before. Didn't someone say that the dye of
>the indigo plant is chemically the same as that of the murex? Indigo is no
>longer grown much because the dye can be synthesized from coal tar. The
>blue dye used for blue jeans is the same or a very similar compound, is it
>not? What makes it purple in one case and blue in another?

According to Gary Rosenberg's Encyclopedia of Seashells, the purple dye of
the murex is the same as that of indigo.  Color shade and intensity is
determined by how long the cloth is soaked.  Another factor may be
variations in the use of color terminology.

It is easy to get muricid-dyed cloth, if you can visit somewhere with Thais
or other intertidal muricids.  Pick them up and they will exude dye.  You
can easily get royal purple-spotted shirts, hands, etc. in this way.

David Campbell

"Old Seashells"

Department of Geological Sciences
CB 3315 Mitchell Hall
University of North Carolina at Chapel Hill
Chapel Hill NC 27599-3315
USA

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FAX 919-966-4519

"He had discovered an unknown bivalve, forming a new genus"-E. A. Poe, The
Gold Bug