Message: I would like to dye a white sweater black. It is 60% polyester & 40% cotton. Can it be done?

It's possible, but I strongly suspect that it will not be practical for you.

First, there is no single dye that will work on both cotton and polyester. You would have to buy two different dyes in order to dye all of the fiber in the sweater black; if you dye only one of the two fibers, you will get a pale to medium gray. Ordinary dyes, such as Procion dye or even Rit dye, will not work at all on the polyester in your sweater. They will just wash out.

Secondly, you will have to invest in a large stainless steel or enamel dyeing pot, because there is no dye for polyester that does not require extensive boiling. You will not be able to safely reuse this pot for food, because all textile dyes are considered unsafe for use in containers used for food preparation. You cannot use an inexpensive aluminum pot for this, because aluminum can react with the dye or the auxiliary chemicals, turning the metal dark and altering the colors of the dyes. A large stainless steel pot is an excellent investment if you are planning to use hot water dyes again in the future, but it's too expensive simply to change the color of a single garment.

A third problem is that cotton shrinks when exposed to high temperatures. If you boil your cotton/polyester blend sweater for an hour, as is necessary to dye the polyester, then the cotton fibers in the yarn will shrink. I cannot predict whether or not this will render the sweater unwearable for you.

To dye both the cotton and the polyester, you can use two different steps, one to dye the cotton, and one to dye the polyester. This is necessary in order to use the highest-quality hand dyes for cotton, which are the fiber reactive dyes, which keep their colors through many washings. Alternatively, you can use a direct dye on the cotton at the same time as the disperse dye for the polyester. This is the method Jacquard Products recommends for their brand of polyester dye. You can mix their "iDye" dye, which will dye only the cotton, with their "iDye Poly" dye, which will dye only the polyester.

The direct dye in the "iDye" for cotton is not particularly resistant to washing out. In order to render direct dye permanently non-fading, it is important to use a commercial dye fixative, such as Retayne, after you have finished dyeing and washing out excess dye from the sweater. Alternatively, you can hand launder the sweater in cold water, separately from other garments, to avoid problems if the dye runs in the wash.

To dye this cotton blend sweater, here is your shopping list:

• One three-gallon or larger stainless steel or enamel cooking pot (do not reuse this pot for cooking food!)
• One long-handled spoon, to be used to stir the sweater constantly throughout the dyeing process
• One or more packets of iDye dye (use more dye for a darker black)
• One or more packets of iDye Poly
• One bottle of Retayne or another cationic dye fixative

Do not omit any of these items, if you want to dye your sweater a dark black. You must buy both kinds of dye, in order to dye both of the fibers in your sweater. As you can see, the expense of this project is probably much more than the cost of just buying a new sweater.

If you don't want to go to that much trouble, consider dyeing your sweater a different color. If you try to dye a polyester/cotton blend garment with just cotton dye, you will get a paler, more muted color. If you use black dye, you will get gray; if you use red dye, you will end up with pink; if you use bright purple, your sweater wil turn a pale lavender. I recommend that you use Procion MX fiber reactive dye, which can be used in cool water, with no need for a cooking pot at all. This will save dramatically on the effort and expense involved in recoloring your sweater. You can buy Procion MX dyes from a good dyer supplier, or you can buy it from a crafts store under any of several different brand names. Look for Jacquard Procion MX dye, or Tulip One Step Fashion Dye, or Dylon Permanent dye. Any of these dyes will change the color of your blended sweater to a pastel color, which will last for years in spite of many washings.

I do not recommend that you use another hot water dye, such as Rit dye, because all hot water dyes require heating for best results, which means that you have to invest in the dyeing pot. Like fiber reactive dye, Rit dye will fail to dye the polyester in your sweater, but it can dye the cotton. Cool water dyes are much easier to use than Rit dye, require less expensive equipment, and last much longer without fading.


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