Message: Hi.  I am researching a method in which to tye dye cycling socks made with 60% nylon, 39% "coolmax" and 1% lycra.  I see that there is idye poly on the market but wasn't sure whether I needed this in conjunction with regular idye.  If I overlooked any info about coolmax, I apologize.  Thank you so much!! 

You can't use iDye Poly, or any other brand of disperse dye for polyester, on anything that contains spandex. Spandex is very heat-sensitive and will be shredded by the extensive boiling required to dye polyester. Both iDye Poly and regular iDye (a direct dye which works only on cotton and other cellulose fibers, plus silk) are hot-water dyes, unsuitable for any spandex blend.

This means that I do not advise dyeing the 39% "Coolmax" polyester in your socks at all. I advise trying to dye polyester only when there is no spandex in the garment at all. When you see polyester/spandex clothing that is colored, the spandex and the polyester were dyed separately before they were combined into one fabric.

Nylon can be dyed at lower temperature than polyester, but it does require some heat. High heat, close to boiling, is the best for dyeing nylon, but you can dye some nylon at lower temperatures, though you cannot dye it at room temperature. You can experiment with using acid dyes at 140°F to dye your socks. You must do tests to determine whether the wear properties of the socks are significantly damaged by the effect of the hot water on the spandex. You will find that your colors are much paler when you dye a 60% nylon blend than they would be if you were to dye a 90% or 100% nylon fabric, since the polyester in the blend will not take the color at all.

An alternative is to use fabric paint, rather than dye. Fabric paint is often not as satisfactory as dye, in cases when dye will work, because it sits on the surface of the fiber, instead of penetrating it. This means that it wears off more quickly than dye. Items colored with fabric paint should always be turned inside-out before laundering. It also means that the feel of the fabric is slightly changed by the fabric paint, though this is much less of a problem with high quality fabric paints. Try Dye-na-Flow, which is a fabric paint designed to flow like dye, or Dharma Pigment Dyes, available only from Dharma Trading Company. This is the only form of color I can recommend for dyeing your 60% nylon, 39% polyester and 1% spandex socks.

A better alternative would be to find a source for more easily dyeable socks, if possible. For example, a cotton/spandex blend can be dyed easily and with very intense colors, using a cool water fiber reactive dye such as Procion MX, the dye that is found in all good tie-dyeing kits. A spandex-free polyester sock could be dyed with iDye Poly. The main thing you have to avoid is any blend that contains both spandex and polyester. Note that acrylic is just as difficult to dye as polyester, so an acrylic/spandex blend would not be at all useful for tie-dyeing.

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