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Washable Wool

November 9, 2006

A listener asks: How does wool become non-shrink?


Shrinkless sweaters. I’m Bob Hirshon and this is Science Update.

That chill in the air means it’s time to dig up our musty old sweaters, which may be why listener Christie Rowe from Moss Landing, California, asked how some wools are made washable. We turned to wool researcher Jeanette Cardamone of the Agricultural Research Service.

JEANETTE CARDAMONE (Agricultural Research Service, US Department of Agriculture):
And it has to do with the structure of the wool fiber itself. The wool fiber has scales on its surface and it looks very much like shingles on a roof.

When normal wool is washed, these rough scales lock together and make the fibers shrink. But some chemical treatments, including one that Cardamone invented, can make the scales smooth and unable to lock together—meaning your sweater’s size is safe.

If you have a science question, submit it at If we use it on the air, you’ll win a Science Update mug. I’m Bob Hirshon, for AAAS, the science society.