Dyeing Superwash

by | Feb 25, 2021 | Happy Valley, News, Rodanthe, Yarn

Published: February 2021
First picture of undyed superwash and non-superwash yarn

Undyed skeins showing difference in color between superwash treated and regular wool.

I have to admit, I am a fiber snob and tend to shy away from superwash* type yarns. They tend to feel different to me than untreated yarns and I’ve had the luxury in my craft-life to just not care if my handknits are machine-washable or not. However, as a dyer, they flat out intrigue me.

So, why, oh, why do they dye so differently than a yarn spun from the same, untreated, fiber?

Years ago, a company came out with a yarn that seemed pretty magical – a single color barber-pole effect! Since I hadn’t ever dyed superwash treated yarns at that point, it didn’t occur to me that it was actually made of 2 singles of the same fiber – but one was superwash treated and the other wasn’t!

At that point, I did start to dabble a bit, dyeing random bits of superwash yarns just to see what would happen.

And that led me down the rabbit hole of finding out why. Why do superwash treated yarns look darker than their untreated counterparts with the same amount of dye? Hopefully I can explain without making your eyes roll back in your head from my nerdiness.

Did You Know?

Dye follows water into the fiber.

Wool has a dual nature. It is naturally both hydrophobic (repels moisture) and hydrophilic (absorbent). In simple terms, small amounts of moisture (think dew drops) will sit on top of a wool sweater until a certain moisture level is reached (hydrophobic) and then BOOM, wool will start absorbing the moisture into it’s fibers (hydrophilic.)  Regardless of the type of superwash treatments, they all change the surface of the wool fiber to increase it’s hydrophilic nature. This could easily explain why superwash treated yarn takes up dye faster and exhausts the dye bath more quickly.

Superwash treatment = more dye sites.

Research also suggests that all superwash treatments etch the surface of the wool fiber somewhat — leading to a) more dye sites on the surface of the wool; b) a higher concentration of dye attaching on the surface of the fiber; and c) the appearance of a deeper depth of shade than might appear on the same untreated yarn.

The finish reflects light differently.

In addition, most superwash treated yarns have a type of resin applied to assist with the prevention of felting. This also affects the reflective qualities of the fiber – again adding to the appearance of a deeper depth of shade.

Yellow fiber tint from chlorine.

And last, but not least, while superwash yarns are obviously lighter and brighter, many of these treatments involve chlorine which leaves the fibers slightly yellower than their untreated counterparts. Again, dyeing over fiber that is not quite pure white, may lead to a slightly deeper depth of shade. And, the underlying yellowish tint may change the hue of your dyes – especially for the lighter depths of shade.

Comparing length and twist of washed, relaxed skeins.

Left – Relaxed Happy Valley (superwash) skein is longer than Rodanthe skein. Right- Same angle of twist on both skeins (Happy Valley on left side of pink line.)

So, let’s take a walk on the wild side while dyeing and comparing two of our yarns made with the same fiber to see how research might meet reality.

Both yarns are 3-ply and were made side-by-side on the same spinning and folding (plying) frames with all spindles set to the same twist and fold ratios. The first thing to notice is that Happy Valley (the superwashed version) appears longer in it’s relaxed state. The superwash treatment inhibits both shrinkage from felting but also from “relaxation shrinkage.” Relaxation shrinkage is related to the release of mechanical stresses introduced into fibers during manufacture.  This means that untreated yarn (Rodanthe) had more freedom to relax and remember it’s original crimp.

On the right, you can see that the angle of twist on both skeins is the same at this point.

After scouring — they hang the same.

But look, while in the dye pot — with the same recipe and depth of shade — they are certainly picking up the dye at a different rate.   I deliberately chose a light blue dye to illustrate how much the yellow cast of the superwash treated fibers might affect the hue of the yarn. So far, I see more green in the Rodanthe, giving it a slightly turquise cast as the yarn starts heating up in the dyepot.

Comparing yarns through initial dye stages

1st pair photos: Rodanthe (left) and Happy Valley (superwash on right) — 10 minutes with dye in cold water.2nd pair photos: Same dye pots – another 20 minutes with citric acid, cold water.
3rd pair photos: Same dye pots – water at 100 degrees

I hope you can see the very clear difference between the superwash and non-treated yarns. The right-hand side of each picture is the superwash treated yarn. So, it seems very clear that the superwash treated yarn is picking up the color more quickly and, seemingly, more intensely. But …..

Finished Skeins

Can you tell which is which? It’s a very subtle difference.

But, by the time both yarns have gone through the entire dye cycle and absorbed all the dye in the water — I can’t really tell the difference! While a lighter depth of shade might retain the differences of shown in earlier stages of the dye cycle, it seems that the darker you get — the less difference there is.

So, can you tell the difference? The first 10 registered Mill House customers that send us an answer will receive a free pair of Happy Valley and Rodanthe skeins for their own testing. Use the Mill House Contact form at this link Contact Us

Make up your own mind about superwash vs. untreated yarns.

*The term superwash is not capitalized in this blog post because it doesn’t seem to be currently under a valid trademark as a yarn treatment. Originally filed as a trademark in 1974 by Woolmark, Inc. in New York, it shows as expired in 2006.  Keep in mind that word combinations that include the word superwash may have been registered separately and may still be under valid registration.

Jeane deCoster


Yarn designer, hand dyer, teacher, consultant. Owner (and chief dyer and bottle-washer) of her own indy yarn company, www.Elemental Affects.com.

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