[Sca-cooks] OT animal v plant dyes

[lilinah at earthlink.net]

Jennifer responded to Kiri:
>  > Evidently there are two classes of dyes (Kiri really doesn't
>>  know what she's talking about here...but is quoting what she's been told),
>  > one of which works on animal fibres
>  > and the other works on everything else.
>
>What I've been told on this is that acid dyes (whether that's vinegar and
>kool aid or Procion Acid Dyes) are for animal - wool, dog hair, silk and
>everything in between; Alkaline dyes are for plant - cotton, linen, hemp,
>and  palm tree for all I know.  (And ditto on the clueless and quoting part)
>
>  >> Acids are for protein fibers, including silk, of course.
>  >> Alkalis are for cellulose fibers. Vinegar will weaken cellulose fibers
>  >> and alkali will actually make them stronger.

It isn't a question of the dye itself, but of the mordant and the pH
of the dye bath. Usually the same natural dye can be used to dye
either animal based or cellulose based fiber, but the pH dye bath may
need to be altered to make the dye effective. The color can also be
altered by dyeing a fiber in a bath of a certain pH then dipping the
dyed yarn in a mostly water solution of another pH - and see a very
strong change in color! I'm not sure if this was done "in period",
however, but it is not unusual in 20th and 21st c. natural dyeing.

Synthetic dyes are often designed specifically for a particular type
of fiber and often won't work well on the other kind.

Anahita