Why does wool shrink?

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โˆ™ 2009-03-30 05:26:44

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Wool does not shrink, it felts. This is caused by the raised scales of the cuticle layer of the wool fiber catching on one another. The fibers in a fleece on a sheep are all growing out of the follicles in the same direction and they generally grow at a similar rate. This means that the cuticle scales (which are a bit like the teeth on a saw blade) are all pointed in the same direction. They don't catch on one another. These scales can be seen clearly under a microscope.

After the fleece is shorn, the processing stages cause the natural fibers alignment to be completely disrupted. As the fleece is cleaned and scoured, the "staple" structure is destroyed and the fibers no longer line up "tip to base" as they would in the fleece. The fibers end up in all dimensions and suffer entangling after scouring and drying. The purpose of washing and scouring is to remove unwanted materials and to disentangle and align the fibers into a parallel arrangement for spinning yarn. However the fibers will not necessarily be "tip to base". The scales now can be at 180 degrees to one another, which can cause them to catch on each other.

When the fibers are spun, they come in close contact with each other, and the interlocking nature of the scales is what helps keep the yarn together. Felting usually occurs in the presence of heat, water and agitation, and this acts as a ratchet, tightening the contact between the fibers in the yarn, and then the yarns in the fabric.

Wool tends to felt is because of the scales on the fibers. Other animal fibers have cuticle scales too, but to varying degrees. For instance, the cuticle scales on human hair are much flatter. Fine diameter wools are more likely to felt than broad diameter wools because they have a greater surface area, and hence more scales proportionately.

Shrink-proofing is a chemical treatment of wool, which uses chlorine to "burn" off the scales. This doesn't entirely remove them, but it does lessen their profile. The fibers are then coated with a resin to smooth them further. This allows the wool to be machine washed without felting / shrinkage.

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Related questions

Do wool menโ€™s socks shrink when washed?

Wool socks, like all wool clothing will shrink when washed. However due to the blended wool it is unlikely that wool socks will shrink much.

How can you shrink a fitted wool cap?

Agitation in water can cause wool fibers to 'shrink', and the process is unpredictable.

Will a wool coat shrink if it gets rained on?

Yes wool can shrink if it is rained on, especially if it is humid outside.

Does wool shrink if you put it in the dryer?


Does wool shrink after going in the wash?


How do you shrink a wool blend coat?

A wool blend coat has been designed not to shrink, based on the blend of the wool. However, you could wash the wool coat in hot water with maximum agitation, which affects the wool, but not the blend. Your results would be unpredictable.

How do you shrink wool clothing?

wash in very hot water

Why does cotton wool shrinks in water?

Cotton wool -- absorbent cotton -- absorbs water, and would not shrink.

How do you get wool not to shrink?

You can not get it to shrink. If you wash somthing and you dont want it to shrink by putting it in a dryer then just hang it up some where and let it dry.

How do you shrink alpaca wool sweaters with out hurting the item itself?

The best way to shrink alpaca wool sweaters is by washing them in hot water. During the process, you want to keep checking the size, so that you don't shrink it too much.

Do wool felt hats shrink?

Only a small amount if any.

How do you shrink a wool cap?

Wool shrinks when it is agitated in hot water. You may not be able to control how much the cap shrinks.

Is merino wool washable?

Yes but I would read the instructions on the wool wash you use so the garment doesn't shrink.

How do you dry a wool blanket?

Wool is best dried in open air, since agitation can cause wool to shrink. Dry it flat so as to retain its shape.

why wool has to be very carefully washed to avoid damage?

so it doesnt shrink

Why can't you wash wool pants?

you can't wash wool pants because they will shrink in the wash then you will not be able towear them. this is why you have to wash them by hand.

How often should wool clothing be washed?

not very often as it may rip or shrink

When you wash a wool sweater in hot water does it permanantly shrink?

Yes, and when it shrinks it is permanent.

How do you wash 100 percent wool decorative throw?

You don't. Have it dry cleaned or it will shrink.

What happens to wool when wetted?

If you wet it with hot water like washing it it could shrink.

Does water hurt wool?

"Hurt" here requires a context.When you wear your wool jumper in the rain, you can dry the jumper and have no trace of 'hurt'.If you agitate your wool jumper in hot water, it will shrink.

Will a polyester wool blend shrink in the dryer?

I tried to shrink coat that is a 60%wool/40%polyester blend by washing it in hot water and drying it on high heat. It didn't work. In my case, I think the company's labeling may be suspect.

Does cold water shrink clothes?

Warm and hot water is known for shrinking clothes at times, especially wool or cotton clothing. Cold water will not shrink clothing.

Do llamas have fur or hair?

Llamas actually have wool similar to that of a sheep, however it does not have the oil that sheep wool has. It is called fiber while on the animal. It is finer than sheep's wool and only one percent of it will shrink.

What is Rachel Makinson famous for?

because she advanced in textiles and design by doing research in non-shrink wool