Answer Man: Why do your clothes shrink in the dryer?

McClatchy-Tribune Information Services

Q: What is the science behind clothing (especially cotton T-shirts) shrinking in the dryer? We try to hang ours up because of this phenomenon. Also, can shirts that have shrunk be "unshrunk?" Lastly, where do the socks that disappear in dryers and washing machines go?

A: You may have heard that if you’d measure your height when you get up and again when you go to bed, the result would differ by anywhere from a half to three-quarters of an inch every day. Just the stress of gravity as we sit and walk compresses the discs in our spine by forcing fluid out of them. Then, as we sleep, the discs reabsorb the fluid, plumping them up for another busy day.

Similarly, it’s a stress-relaxation cycle that can shrink your clothes if you’re not careful. Only here the process occurs in reverse and generally cannot be undone. Here’s why — and I hope you’re willing to wade through a little scientific mumbo jumbo from Sai Janani Gansean at the University of California at San Francisco:

Your T-shirt, of course, is cloth woven together from threads which themselves have been made from cotton fibers. These fibers (now bear with me) are actually long molecular chains linked end-to-end by hydrogen bonds. As these fibers are spun into thread and the thread into cloth, the fibers get pulled, stretched, and twisted. So when we buy the shirt, it’s at its most stretched-out state, as it were, and those bonds holding everything together are, in human terms, stressed out.

So, just as you jump in a warm sauna to relax after a hard day, putting the cotton T-shirt into hot, agitated water and then a hot dryer relieves the stress on the hydrogen bonds so those molecular chains return to their original size. As a result, the fibers, threads and cloth get smaller and the shirt that once fit you so well may have to be handed off to your 10-year-old.

(Wool works a little differently. A wool fiber has tiny scales arranged like shingles on a roof. When they encounter heat, water and the washer’s agitation, the scales clump together, tightening the fibers in the yarn and the yarn in the fabric. The end result, however, is the same although rewashing and reshaping might help.)

That’s why you should always follow washing instructions religiously or buy clothes with man-made fibers or those labeled "pre-shrunk" since they have already been washed a time or two. Air-dry or use the lowest settings. If you goof and wind up with something that seems to better fit your cat, you might try pressing with a hot iron, but no guarantees.

As for those wayward socks, I was at first going to answer your facetious question with an equally playful answer. For example, famed physicist-cosmologist Stephen Hawking once jokingly speculated that they disappeared in space-time through tiny, spontaneously generated black holes. Others blame sock puppets in search of a new body or the need to join Jimmy Hoffa on a cruise to the Sargasso Sea of Socks.

But wouldn’t you know it? Just last spring after extensive research, an English psychologist teamed up with a statistician to develop the Sock Loss Index — your odds of winding up with an odd piece of footwear. I’ll spare you the details, but it’s a lengthy algebraic formula that involves laundry size, number of weekly loads, complexity of those loads, how much you like doing the laundry, and the number of socks washed per week.

Among their findings, which blames everything on human error: The person doing the wash often incorrectly assumes that all other family members are diligent about throwing complete pairs into the hamper. Hence, odd socks pop out of the dryer while their mates gather dust in the sofa or under the bed. Also, behavioral errors of omission and commission.

"Omission is demonstrated when someone sees a sock on the floor, for example, and fails to pop it into a wash bin or washing machine," according to the study that was commissioned by Samsung to help launch its new AddWash washer that allows owners to pop in items during a cycle through a second door. "Commission is when we do something we shouldn’t, like sneak a white sock into a dark wash or hide it in a random place to avoid having to find its mate."

The result is that the average Briton loses 1.3 socks per month or 1,264 over an 81-year life span at a cost of perhaps $3,000-plus.

Of course, by now, you’re probably wanting me to, as they say in Britain, put a sock in it.

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