If it's caught in a warm rain, why doesn't a sheep shrink?

Question

Hmmmmm.

Answer 1

because when wool is spun (the process of straigtening and stretching it) it will shrink but in the natural state (on the sheep) it is no different than any other hair or fur. Heat to processed wool just makes it try to revert back to it's natural state (tight and curly)

Answer 2

That is the best question I have been asked in a long while. I do ot know.

Here is the answer:

http://www.madsci.org/posts/archives/oct2000/970761460.Bc.r.html

Hi there Rebekah,
Well I had no real idea myself, so I turned to a real expert in wool science. This is a very popular and important industry in Australia and New Zealand, where a number of good univeristies run degrees in wool science and production...so to there I turned.

Here is the response I recieved from Miss Helen Daily, who is a professional woolclasser and more than qualified to make this response. You can find more information via the Woolwise website:

"The problem lies in the professor's misinformed question. Wool does not shrink, it felts. And this is simply because of the raised scales of the cuticle layer of the fibre catching on one another. The fibres in a fleece on a sheep are all growing out of the follicles in the same direction, and generally speaking, they all grow at a similar rate. This means that the cuticle scales (which are a bit like the teeth on a saw, but not that pronounced) are all pointed in the same direction. They don't catch on one another. These scales can be seen clearly in electron micrographs. (some available on the Woolwise site).

After the fleece is shorn, the processing stages cause the natural fibre alignment to be completely disrupted. As the fleece is scoured, the "staple" structure is destroyed and the fibres no longer line up "tip to base" as they would in the fleece. They can be in all dimensions and also suffer entangling after scouring and drying, and the purpose of subsequent carding and combing is to remove extraneous matter and disentangle and align the fibres into a parallel arrangement. However the fibres will not necessarily be "tip to base". The scales now can be at 180degrees to one another, and can catch on one another.

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

Wool's propensity to felt is because of the scales on the fibre. Other animal fibres have cuticular scales also, but to different degrees. For instance, the scales on human hair are much flatter. I don't know much about dreadlocks, but I imagine this is caused by interrupting the usual parallel arrangement of the hair scales. 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, and then the fibres are coated with a resin to smooth the fibre still further. This allows the wool to be machine washed without felting, and the shrinkage of the fabric associated with felting. So that is the story of wool felting in a nutshell. The wool proteins are very interesting, but really don't play a role in this part of the wool story!"

Thanks for that Helen!....and I hope that answers your question Rebekah. I certainly learnt something new!

All the best

Jim Caryl
MAD Scientist

References:

Helen Daily at the University of Adelaide & The Woolwise Website.

Answer 3

All ya'll so stupid!!!!! I grew up on a ranch. When the sheep is still wering the wool, in a way it's alive. And it has somthing called lanolin in it. When the wool is cut of, they clean all the lanolin out, then it goes through prosessing. After all the prosessing is said and done, the wool is a light, warm material. In a way, dead. The only thing that keeps it from shrinking on a sheep is the lanolin.

Answer 4

From what I've read and heard -- sheep's coats, when doused, become quite heavy and swollen... I think.

Your woolen sweater shrinks -- mostly likely because of the way it was manufactured and sewn. Natural wool carries water, and insulates, making it extremely heavy.

Hope that helps -- ! =)

Answer 5

Because it's fur wasn't pulled into fine threads, and processed, into a linen, in one fine sheet. It's afro of wool, only puffs up, and becomes heavier when weathered.

Answer 6

Because cotton has to go through the dryer too....then it shrinks

Answer 7

Oh, he just inhales until it passes then exhales and stretches it all back out. Much like a freshly washed pair of jeans. =)

Answer 8

thats a good question ithink it has to do with how its still growing when its on the sheep

Answer 9

Woolite.

Answer 10

because it isn't knit. Also it's more the hot dryer that shrinks it.