Name: Estefani

Message: Hi, I just bought leggings that are made out of rayon and polyurethane. They are gray and I want to dye them black. what kind of dye do you recommend?

The polyurethane is probably the stretch fiber. Lycra® spandex is made from polyurethane.

In most cases, the thread from which these garments are woven or knitted are made by spinning cotton or rayon fibers around a stretch polyurethane core. As a result, the synthetic fiber is not on the surface where you can see it or feel it, except when the fabric is actively being stretched. 

This means that the best way to dye most such blends is by dyeing only the cellulose fiber, in this case the rayon, using a cool water dye. There is no need to dye the polyurethane itself, because it is hidden. This is a good thing, because the temperatures required for successful dyeing of polyurethane will probably make any garment that contains it lose its shape. Polyurethane requires a different sort of dye than rayon does; you're better off not even trying to dye it. So, just ignore the polyurethane, except as an inspiration to keep the water temperature low, and get a good dye for the rayon.

I recommend that you use a fiber reactive dye, such as Procion MX dye, at temperatures below the maximum for laundering as indicated on the care label. Procion MX dye works very well on viscose rayon at room temperature. If the care label does not specify the maximum temperature, keep it below 105°F (41°C). Drimarene K dyes are also highly suitable. Remazol fiber reactive dye prefers higher temperatures but will work at 105°F. Avoid using any hot water dye, including all "all-purpose" dyes such as Rit All-Purpose Dye or Tintex Easy Fabric Dye, because the heat required to set these dyes is likely to damage your leggings.

For more information, please see my page "How to Dye Spandex".

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