Why Do Sweaters Shrink When Washed, But Sheep Don't When Caught in the Rain?

[daveed]

how come sweaters shrink when you wash them, but sheep don't when they get caught in the rain

my ap bio teacher asked us that in class, and nobody had an answer

 

[Moonbear]

I don't know if this is really correct or not, but it sounds plausible at least.

http://www.sdreader.com/php/ma_show.php?id=101603A

 

[Ivan Seeking]

how come sweaters shrink when you wash them, but sheep don't when they get caught in the rain

my ap bio teacher asked us that in class, and nobody had an answer

That is hilarious!

I'm thinking...

EDIT: Sounds good to me Moonbear. That's exactly what I was about to say.

 

[hitssquad]

Lanolin and the mysterious non-shrinking wool

how come sweaters shrink when you wash them, but sheep don't when they get caught in the rain

As Moonbear's article says, part of the reason is the oil in the sheep's wool:

• Main Entry: lan·o·lin
  Pronunciation: 'lanølðn
  Variant: also lan·o·line \", -øl,En\
  Function: noun
  Inflected Form: -s
  Etymology: International Scientific Vocabulary lan- + -ol + -in, -ine; originally formed as German lanolin
  
  : wool grease refined for use chiefly in ointments and cosmetics: a : a yellowish sticky unctuous mass absorbable by the skin and containing incorporated water — called also hydrous wool fat b : a similar brownish yellow anhydrous mass — called also anhydrous lanolin, refined wool fat

Hand cleaner sold at auto-parts stores sometimes has lanolin in it. http://paint-and-supplies.aubuchonhardware.com/cleaners_and_thinners/hand_cleaner_and_go_jo.asp is a webpage with several examples.

 

[Moonbear]

Lanolin is a great moisturizer!

But there is nothing worse than having to catch a soaked-through sheep ...except maybe being the soaked-through sheep. They can take days to dry off if caught in the rain long enough to get completely soaked, though the lanolin helps keep them water-resistant for a while.

 

[Imparcticle]

Does lanolin keep the sheeps' wool or hair from tangling?

 

[Andre]

Felting is one mechanism, tension relaxation is another. During the manufacturing of wool, cotton, etc, the fibres are stretched out in the process. This is reversible and the relaxation may be speeded up by the higher temperatures in the washer.

 

[Moonbear]

Felting is one mechanism, tension relaxation is another. During the manufacturing of wool, cotton, etc, the fibres are stretched out in the process. This is reversible and the relaxation may be speeded up by the higher temperatures in the washer.

Yes, if you look closely at the wool on a sheep, it's very kinky and curly. It has been smoothed out before being used for making sweaters. Plus, the wool on a sheep isn't woven around it's body, it's sticking out from their skin in individual strands (some get tangled together, but they are still all pointing in the same direction). So, if they get wet and more curly, the fibers will only shorten inward toward the sheep's body. With a sweater, the fibers point in all directions, so if they shorten, then this makes the entire garment shrink in all directions.

I'm just thinking through this as I go along too, so I don't know whether felting or curling is more to blame. Does wool curl under the same principles as hair curls, via disulfide bridges? I'm wondering if the moisture and heat helps activate reformation of some of those bridges that may have been broken in the processing of the fibers?