Name: Pablo

Country: USA

Message: You have mentioned that cotton/polyester blends are hard to dye.  Unfortunately, my favorite brand of pants are an all-black, 55% cotton, 45% polyester blend.  They fade over time, or right away if washed or rinsed in cold water.  The stitching stays solid black.  When looking at a faded pair, it looks like there is a diagonal pattern of threads that stay fairly dark and others that have faded.

Is it possible that only the cotton or only the polyester part of the blend is fading?  If so, which would be a likely candidate to be re-dyed so that the pants will be dark black again?

That's an interesting question. Which dye is fading, the polyester dye or the cotton dye? It could be either. We can't tell for certain from the fact that the polyester thread is not fading, because it was most likely dyed by an entirely different manufacturer, possibly with an entirely different dye.

It's a lot easier to dye cotton than it is to dye polyester, so it would make sense to try dyeing the cotton first. Dyeing the cotton is cheaper, too, since it won't require that you invest in a special cooking pot for boiling the clothing in the dye. (You should not plan to reuse a dyeing pot for food preparation.) The most permanent dyes for cotton are fiber reactive dyes, which can be applied in a plastic bucket or in the washing machine. You should avoid all-purpose dye, such as Rit or Tintex, because it fades quickly in the wash.

There are several different types of fiber reactive dye available. For a single garment, you can go to a crafts store or a sewing store and look for either Dylon Permanent Dye or Tulip Dye; both of these include fiber reactive dye, plus the additional chemicals to set the dye. Weigh your garment first, while it is dry, so that you will know how many packets of dye to buy. A one-pound pair of 100% cotton jeans will require two to four packets of Dylon Permanent dye; your 55% cotton jeans should require only half as much, but it's best to use plenty of dye to get a dark black, so I'd recommend you use two packets per pound of fabric.

For dyeing in the washing machine, which is an excellent way to get a perfectly smooth even color, see my page, "How can I dye clothing or fabric in the washing machine?", as well as this earlier questions: "I want to get the deepest darkest black I can get". You'll probably want to buy at least eight ounces of Procion MX dye from a good mail-order dye supplier, along with soda ash; for washing machine dyeing, you will also need a large quantity of ordinary table salt.

I think that this will work for you. I think that your fading black dye is most likely an inexpensive direct dye, which is a type of dye that's notorious for rapid fading. (It's one of the two types of dye included in all-purpose dyes, such as Rit.) If I am wrong, then you will see the cotton stay dark, and the polyester continue to fade. Dyeing polyester is a pain, because it requires that you use only a special kind of dye known as disperse dye; this type of dye works only when you boil the garment with the dye for some time. This requires a dyeing pot large enough for the garment to move in freely, most likely a five-gallon stainless steel or enamel cooking pot, which will probably cost you at least fifty or a hundred dollars. Dyeing cotton is much easier and less expensive than dyeing polyester, since you don't need to invest in a dyeing pot.

If you buy a new pair of pants, you can immediately treat it in hot water in the washing machine with a cationic dye fixative, such as Retayne. This stuff works great to make direct dye much more permanent on cotton. Unfortunately, it is likely to have little effect on the polyester. See "Commercial Dye Fixatives". You can buy Retayne and similar dye fixatives by mail-order. There is no need to use Retayne on fiber reactive dye that you apply yourself, because proper reactive dye fixing with soda ash is both easier and longer-lasting, but it's a good way to stop poor-quality dyes from fading.

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