How bleach affects yarn

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What is the best way to care for handmade clothes? One of many products in a typical house, that can be used on laundry, or come in contact with laundry, is bleach. So I poured some bleach onto some yarn. Just to see what would happen …

Pouring bleach onto my yarn – how, why, and be warned!

I love my handmade clothes. From my crochet hook, knitting needles or sewing machine, these are the things I love to wear. Therefore, they are also the ones that end up in the laundry basket most. And sometimes I get very nervous washing them. Different web sites say different things. Many of them seem to suggest you can’t just fling your hand makes into the machine with the rest of the wash. And when you are a low-energy spoonie like me, that’s intimidating. I really don’t have much energy in reserve for hand washing.
Then there are costs to think about, and the environment to consider. Are more expensive detergents worth it if you are on a budget? And do our laundry habits impact our ecological footprint?
Too many questions to answer in one go. So in this post, I’m just looking at the effects of bleach on our clothes.


I put some strands of yarn into 2 dishes. I filled one dish with water, and added a small squirt of bleach. This would be like the effect of just going through a couple of washes.

In the other dish I added pure bleach. This would show the impact of lots of bleach. In normal laundry, what might happen to a garment over many washes.

I planned on leaving the yarn in the bleach overnight, and headed to bed. But after a couple of hours and 6 puffs on my inhaler I went back down and got rid of all the bleach from my kitchen so I could breath again. Because I’m such a silly goose I forgot that bleaching the floors sometimes triggers my asthma. I was so caught up in the idea of the blog post, that I didn’t think of my health. It was all OK, my breathing settled down. And the short time the yarn was in the bleach was more than long enough to show reactions. There was no problem getting photos of how the yarns had bleached.

But note to self: safety first when doing kitchen science experiments! Don’t be a silly goose and get so caught up in a ‘good idea’ for a blog that you do dangerous things.

What is bleach? Why does it affect yarn and fabric?

The original meaning of the word ‘Bleach’ is to remove colour from fabric, paper or other materials, to make it white. Sometimes this is so that it can then be dyed a new colour.

In history, fabric was bleached in bleaching fields. The fabric was woven, then laid on the Bleaching Field for the summer. There it would slowly turn white over months due to the effects of the sun and rain. Then it was finally taken for washing and dying. Our very first, and most ‘natural’, bleaches are sunlight and rain. But this process takes months, or maybe years to work properly, depending on what you are trying to bleach. Enterprising people have looked for chemicals that will bleach for hundreds of years. This makes life easier for those who want to produce fabric, yarn or clothes. Imagine how many cows we would need to get rid of, if we needed to go back to using bleaching fields. And how long it would take to make one ball of yarn.

Nowadays, when we say ‘bleach’, sometimes we still mean the process of taking colour out of something so we can dye it. But most of the time we mean the chemicals we use instead of sunlight. If I say ‘I bleached my hair yesterday’ then you know I used chemicals to take all the colour out of my hair, ready to dye it in rainbow colours. But if I say ‘I bleached my sink yesterday’ you know I used some chemicals we call ‘bleach’ as a shorthand, and disinfected and cleaned my sink. Which is still metal colour, and didn’t turn white at all.
Most importantly, in these 2 examples, we are actually talking about 2 different chemicals, both of which are often called ‘bleach’. You bleach your hair with peroxide. But are more likely to clean your sink with some form of chlorine. Which you don’t ever want to touch your hair, and you will probably see the reasons for that below.

The type of bleach that is generally sold as a cleaning/disinfecting solution is a chlorine based substance.

The thing about bleach for cleaning clothes is that it’s great for taking out stains. The thing that’s not great about it is that it takes out colour. And it can damage the fibres over time.
Because it gets clothes clean, it is sometimes found in small amounts as one of many chemicals that make up typical laundry detergents.

So, what happens when we pour bleach on yarn? lets see…

In my previous blog post ‘Science with Yarn’ I discuss the main types of yarn – animal, vegetable and mineral, and how they are different from each other. Here, I’m looking at how these categories of yarn react to bleach.

how bleach affects plant based yarns

The strands of cotton and the strands of linen put into the bleach lost their colour. The cream linen turned white, while the dark purple cotton turned creamy white in the pure bleach, and the cotton in the water with a splash of bleach faded to a patchy pink/cream.

Other than the marked change in the colour, the yarn didn’t show any signs of damage. I could imagine myself washing it, and using it as white yarn.

Viscose is a plant based yarn. But unlike cotton, linen or Ramie, is is a synthetic. In other words it is manufactured through chemically dissolving bamboo, wood chips or other plant based matter. Then creating a new substance from the goop, which are fixed and spun in a similar way to acrylic.

It is therefore interesting to see if rayon will behave like a plant based yarn, or if it will behave like an acrylic, as it has aspects of both.

The answer here is that, when bleached, rayon reacts the same way that cotton and linen do. It would appear from this experiment, that its safe to assume that rayon is a plant based yarn for laundry purposes.

How bleach affects animal based yarns

The wool was eaten by the bleach. I left a strand of wool yarn in some bleach, and came back to a few scraps of fibre to hint at where the strand of wool used to be. The effect on the wool in water with a small squirt of bleach was, unsurprisingly, less dramatic, but the strand of yarn was damaged and beginning to come apart.

And this is why peroxide is used to bleach hair, not chlorine, and why smart people wear swim hats in the pool. Chlorine eats wool (aka animal hair). And it can do the same to your hair.

So what to yarn manufacturers do? If they start with some sheep fleeces in creams, browns, greys and blacks, and want to create colourful yarns? They use highly specialised peroxide based wool safe bleaches, that a normal household wouldn’t have access to.

How bleach affects mineral based yarns

Unlike the wool, the acrylic didn’t dissolve. However, unlike the cotton, the acrylic also didn’t come out unscathed. The strand in the water with a little bleach didn’t show much change, but the strand in the pure bleach showed obvious evidence of damage. Little strands were coming off it, with a fuzziness it didn’t have prior to the bleach bath.

One of the warnings that’s given about using mineral based yarns is that they create ‘microbeads’ in the wash. Tiny fibres too small for the eye to see are shed in each wash, then end up in the waterways and oceans, where they cause untold damage to sea life. Its also very true, as anyone who has ever worn an acrylic pullover will know, that after a few washes, they start to go bally, and need a bit of a shave to look well again.

Looking at the fuzziness of the acrylic after its bleach spa treatment, I wonder if I’m seeing part of this process in action.

The wild card – ‘Milk Cotton’

I had some yarn in my stash I bought ages ago, because I love collecting different and unusual fibres. This one is called ‘Milk Cotton‘. Milk cotton was the original synthetic fibre, before mineral based fibres were even invented. Milk is turned into yarn using the same basic processes behind any other synthetic, such as bamboo, rayon or acrylic. But it’s not very stable by itself, so was traditionally mixed in a 50:50 ratio with either cotton or wool. It became unpopular for a range of reasons, and was almost entirely forgotten when nylon was invented, so you don’t see much of it these days.

I bought this milk cotton directly from China over ebay. As I don’t speak Chinese and can’t read the ball band properly, I can’t even be 100% sure what it is made from. Some text says it’s half milk, half cotton, but other text seems to say its half acrylic. Acrylic is a difficult word, it normally means a specific type of mineral based yarn, but it actually just means synthetic. So a translation from another language might describe the milk as ‘acrylic’ without implying that there is anything other than milk and cotton in the manufacture. I just don’t know, but I poured bleach on it anyway – because, why not? Lets see what happened…

Nothing! Nothing happened. It didn’t even lose its colour. And it didn’t dissolve either, so clearly there was no animal hair in the mix. It also didn’t develop any fuzziness. Does this imply there is no mineral based acrylic in it, and it’s genuinely milk and cotton? It seems to, as in the bleach it behaved like a cotton. What they dyed it with so even the colour didn’t fade in the bleach, I just don’t know.


How best to care for hand made clothes in the laundry – using bleach

Because bleach is commonly used by itself to clean clothes, or as part of laundry detergents, garment care labels and yarn ball bands should have a triangular symbol indicating if the garment is safe with bleach. The symbols are above. Some manufacturers use a solid black triangle, it means the same thing.

The first triangle symbol with no lines through it means that the garment, fabric or yarn can be bleached. The second symbol is an unusual one. I don’t think I’ve ever seen it on any of my own clothes. It means that the fibre can’t be bleached with a typical chlorine bleach, but peroxide bleaches are safe on it. The third symbol, where there is an X over the triangle, means do not bleach this fibre.

This wool cardigan can NOT be bleached!

This cotton says it cant be bleached either. We know from this experiment that is because it would loose its colour


But if we are washing handmade clothes, and don’t have a ball band or fabric label any more with laundry symbols, can we know if it’s safe to use bleach?

The short answer then is:

  • NEVER bleach anything with any wool, alpaca, cashmere, silk or other animal hair content
  • Be VERY WARY of bleaching anything with any mineral content (nylon, polyester, acrylic, etc). It will be damaged, even if the damage doesn’t show for a few washes
  • Possibly bleach plant fibres (cotton, linen, ramie) but be aware that they will probably loose some or all of their colour.

And what about regular laundry detergents?

  • Always use special detergents for wool and silk on anything with any wool or silk content. It’s not just the bleach that can damage them.
  • Be wary of detergents for ‘whites’ or ‘brightening’ on any mineral based fibres. These will likely have more bleach content. Biological detergents for colours will have least bleach, and so be safest. But be aware they are also the most likely to cause allergies.
  • Plant based fibres have one huge advantage. They are the easiest to wash. Bung ’em in, use a trusted detergent, they will likely be fine.

So, the short answer to all of this is that bleach isn’t too good for laundry, even if it gets out stains. Other safe things around the kitchen also get out stains.

If you enjoyed reading this, do sign up for my newsletter to hear about future crazy experiments where yarn is dumped in water, set on fire, and all kinds of fun stuff. Or drop a comment below with ideas for other yarnie experiments you would like to see tried out.


By Ciara

I learned to knit as a young child, and came to crochet much later in life when I could no longer knit. Sharing the joy of crochet with sustainability and slow fashion in mind is a passion

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