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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This page was created: March 23, 2003
Last updated: May 29, 2007
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