One of those 'I wonder why?' questions

Wool clothes mostly have to be dry cleaned because of you throw them in the washer they shrink. But when sheep stand outdoors in a field and it rains they don't appear to get their fur all shrunk. I wonder why?

Answers appreciated and you can list your own 'I wonder why' questions as well.

Is it going to ruin your thread if there is a logical answer?

Water is not actually harmful to wool in and of itself - it is the drying that shrinks it. When wool is still on sheep, it has the ability to continually absorb oils in the sheeps' skin instead of drying out and shrinking like drying in a dryer might do (keep in mind, wool is extremely absorbant).

I like logical answers

Is wool shrinkage due to evaporation of oil, I can't really picture exactly why it shrinks? Does the individual strand of wool hair actually get smaller in volume?

OK.. both water and heat combined are the factors that affect wool combined, but now you made me look for a more thorough answer because I know what happens and what affects it, but I didn't know the actual make up of the fibers to be able to give you a physiological (? what the heck, it's an animal and its fiber, so I'll go with physiological.. lol) answer. Hmm.. how about textilogical or mercantilogical?

At any rate, I had to cheat for the FULL answer, but here goes...

The outside of the wool fiber is hydrophobic—hates and repels water. The inside of the wool fiber is hydrophilic—hollow and absorbs water. Every fiber has a love hate relationship with itself. Even though wool wants to repel water around the fiber, at a certain point of getting wet, it reverses its process of repelling water to absorbing water. When this happens it brings water into it’s core and holds it. In the microscopic view, that is under a microscope, the outside of the wool fibers look like they are made from overlapping shingles, like shingles on the roof of your house. When wool gets wet and heat and agitation is present, wool has a tendency to overlap and lock the shingles. Thus the impression of shrinking is created.

Source: Great Lakes Mercantile website

That was interesting, thank you

Heh.. interesting or boring? The actuality isn't near as much fun as the unanswered question, is it?