community of dyers

That's an interesting question. I don't know the answer from personal experience, but I can give you some speculations to get you started.

Nomex is apparently chemically related to Kevlar (see the earlier discussion Anyone ever dyed kevlar?), but it lacks the high degree of cross-linking required for high strength, so you don't have to worry that the dye would interfere with strength by interrupting its structure, as in the case of Kevlar. As I said about Kevlar, the adjacent placement of the N-H and the C=O groups is similar to that in nylon, so you might expect either acid dyes to work by hydrogen bonding, as they do for nylon, or disperse dyes due to their attraction to large organic molecules as in other synthetic fibers.

The introduction to a 2003 article, "Physical properties of Nomex yarns pretreated with various amines", contains what looks like a good summary of some issues in dyeing Nomex: "Commercially available Nomex is difficult to dye because of its extremely high glass transition temperature. Generally, the recommended method for dyeing Nomex involves high concentrations of a dye carrier in the dyebath, high dyeing temperature, and long dyeing times." The dye carrier that PRO Chemical & Dye sells for use in dyeing polyester is PRO Dye Carrier NSC, though their instructions for dyeing nylon don't even mention it; it is mentioned in their instructions for dyeing polyester. I wonder whether a pressure cooker would work better than extensive boiling, since it reaches a higher temperature. All this is just speculation on my part.

Some people are dyeing Nomex clothing. There's a tutorial on dyeing a Nomex flightsuit a relatively pale color for costume purposes, using Rit all-purpose dye, posted on a Ghostbusters fan forum. Rit dye is unlikely to be among the best choices of dye, but it apparently does work, at least for a pale color, though we don't know how well the guy's results lasted in the laundry later on. Rit all-purpose dye is very easy to find in the US, being sold as many pharmacies and grocery stores. The acid dye included in the all-purpose dye mixture is a type called acid leveling dye; it is notable for producing a smooth solid color but being less washfast than other types of acid dye. I would prefer ProChem's WashFast Acid Dye for dyeing nylon; I don't know if it would be any better on Nomex. You would not expect WashFast Acid dye to work if Rit does not; it might be more washfast, though, if both do work.

Not every part of the Ghostbuster's fans recipe is at all sensible. Dryer sheets (fabric softener sheets) are recommended, the author says, to remove fireproofing, but that's ridiculous in several respects. One is that, if I understand correctly, the fireproof characteristics of Nomex are part of the fiber and cannot be removed by cleaning; two is that dryer sheets do not remove anything, only slick it down, so that they interfere with waterproofing without removing it; and the third is that dryer sheets leave a coating on fabric that is likely to result in splotchy, uneven dyeing. I am, however, no expert on Nomex and cannot be sure that dryer sheets don't interfere with the fireproofing. I would rather you not even try the dryer sheets, just in case it does interfere with the fireproof properties of the Nomex.

Acid dyes are generally more washfast on nylon than disperse dyes, and they are easier to use, so it would probably be a good idea to try the acid dye recipe, possibly with all-purpose dye, before going to the trouble of trying disperse dyes.

In Google Books, Lewin and Preston's 1996 book "Handbook of Fiber Science and Technology" gives a discouraging statement on page 143. It says that cationic dyes (also known as basic dyes) are used for dyeing Nomex because other dye classes exhibit no affinity for Nomex. That does not seem consistent with the hobbyist's claim that Rit dye works.

In conclusion, I don't know how well it will work, but you may as well give it a try on just one piece, perhaps following the tutorial above but with at least twice as many boxes of dye, and see how it goes. I would like for you to test the fireproof qualities of that piece, after dyeing, just to be certain that nothing about the dyeing process has impaired it, though I do not have any particular reason to foresee any problem. If you do try dyeing Nomex, please let us know how it works out!

-Paula