Why do some dye recipes call for Ludigol (or Ludigal)?
What's it used for?
Ludigol is a brand name for m-nitrobenzene sulfonic acid,
sodium salt. (Thanks to Doug Wilson's wonderful Dyes
and Dyeing Glossary for this definition.) It is sold by
PRO Chemical & Dye as Chem
Flakes, as Ludigal F
by Dharma Trading Company, and and as Ludigol F by Jacquard
Products (Rupert Gibbon & Spider).
You do not need to use Ludigol for room-temperature
dyeing. Its use is to protect fiber reactive dye from
being chemically reduced, which is generally considered to
be significant only at higher
temperatures; its use is optional at room temperature. Its
effect, when it is truly needed, is to make dye colors
brighter, improving the yield by preventing their
inactivation before they can bind to the fiber.
Since monochlorotriazine dyes (Procion H type dyes) must be
steam-set, PROchem says that Ludigol is essential with this
class of dye. Dichlorotriazine (Procion MX type) and
monofluorotriazine (Cibacron F, sold by PROchem as Sabracron
F) dyes can be used at room temperature, but they can also
be steamed or microwaved. If heat is used with fiber
reactive dyes, Ludigol is definitely recommended, though you
can get by without it. G&S
Dye says that Ludigol is "Essential for achieving very
sharp edges on painted fabrics."
The only time I've ever used Ludigol myself was after
someone at one of the smaller dyehouses told me it could be
used as a preservative so that Procion MX would stay 'good'
in solution longer, which would mean that somehow it would
quit reacting with the water molecules to become inactivated
by hydrolysis. I immediately bought some, and ran some tests
of my own. To my sorrow, it turned out to be completely
untrue. Ludigol did not extend the lifespan of Procion MX in
solution; if anything, it slightly accelerated the
breakdown.
To keep Procion MX dyes in solution for up to a few weeks,
you can only refrigerate the
dye mixtures, but for much use of stock solutions (which are
handy for avoiding exposure to potentially allergenic dye
powder), you need to switch to less reactive dyes, such as
Cibacron F (Sabracron F), Drimarene K, or Remazol (vinyl sulfone) dyes, or steam-set dyes
such as Procion H.
I've been thinking I should use Ludigol when microwaving
Procion MX type dyes, ever since hearing of Phil
Jones's great results, but, as of this writing, I've
never gotten around to it. My results have been satisfactory
without it.
PROchem, interestingly, suggests using Ludigol in low
water immersion dyeing if you live in a smoggy
environment. I don't know which pollutant they are
concerned about, in this case, nor how significant an impact
it may have.
Jacquard Products recommends using 1 US
tablespoon (15 ml) per
quart (1 liter) of dye solution. PROchem's LWI recipe calls
for 1 level teaspoon (5 ml or 2 grams) of Ludigol per quart (liter).
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