Sometimes, you want to know if dye is going to bleed (or shift) in the wash. This is particularly good to know if you don’t plan to prewash your fabric. What? Missa, you blasphemous cheat! I know, we always want to prewash the bejizzies out of everything, but there are times when you don’t want to, either because you know it shouldn’t bleed but it’s red and you’re using it for bias on a white blouse or because you’re making something that you don’t want any possibility of pre-shrink stretch-out in (like a corset) or whatever, and you just want to know if it’s safe. Here’s a quick test.First off, generally speaking, your petroleum-based synthetics (Poly Ester and her cousins) fresh from the mill are usually safe, because they’re not really dyed – coloring is added to them while they’re still chemical goo.
Natural fibers should be checked, especially cellulosic fibers (cotton, linen, hemp, etc) should always be considered suspect because they’re often dyed with non-chemically reactive solutions. (If you’re looking at hand-dyed yarns and the dyer is careful to let you know they’re using professional, chemically reactive dyes, you can usually rest easy – processed correctly, those really bond to the surface of the individual fibers and will not shift.) Silk also tends to be processed with shifty dyes. (I’ve had a changeable silk re-dye itself in the wash. It went from a glorious turquoise- scarlet changeable to a sort of lilac. Not as much fun….) Wool tends to be less of a bleeder, because it pulls dye inside under the scales of the individual fibers. It’s still possible for it to spit said dye out, though.
Anything you plan to sew to a nylon-based fiber should be checked. Nylon is what’s known as a “dye scavenger”. Nylon likes dye. I mean, it really really likes dye. It’s like a little dye magnet. (So if you’re worried about bleeding in the wash machine, through a pair of nylons in the load. It’s a help.)
To do a quick check for the likelihood of dyes bleeding, you will need a swatch of the fabric in question, and something white. I’m using muslin in this demo, but a coffee filter will also work.
That’s a good sign that this fabric isn’t going to bleed out in the wash.
Now, I sort of expected that this one wouldn’t, because it’s a poly-cotton blend, and the types of dye that can affect both the poly and the cotton are chemically reactive in nature. That’s part of why most commercial bias tape is a poly-cotton blend. But I’m paranoid, and it’s going on white cotton.
If you want to be really, really sure that you’ve moved all of the loose dye particles out of a piece of fabric, you need steam. Ideally, you need to thoroughly wet the fabric and add a touch of a surfactant. (A little bubble bath in a spray bottle of water works shockingly well for this. It’s also great for felting.) Use a hot iron to (literally) boil the water out of the fabric, and you’ll find any loose dye. Specifically, you’ll find it in whatever is underneath your fabric as you do this, so plan accordingly. (Or accept your ironing surface as a fiber-art project in progress. This is my general attitude towards paint and dye transfer.)
This is a bad technique for gentle-wash fabrics. Don’t do it. You’ll be full of sadness….
Kadolph, Sara J., and Anna L. Langford. Textiles. 9th ed. Upper Saddle River, NJ: Pearson Education, Inc, 2002.