Why do clothes sometimes shrink in the wash?

Cloth is made by weaving threads together. The threads are made out of stuff that has long fibers. And anything that has fibers is made out of long skinny molecules. Shrinking is caused by changes in these molecules, so it’s a problem in chemistry.

A wool sweater is a good example. Wool is made of long chain-like molecules of a protein called keratin. In hot water, these molecules develop many bends, twists, and turns. They slide over one another, making shorter fibers. That makes the threads shorter, which makes the whole sweater shrink.

A lot of chemists have worked on this problem.They are trying to make new kinds of fibers that shrink less than natural fibers do.