The mild and mostly wooly history of keeping warm

Having grown up in Houston, Tim Kardatzke was unprepared for winter when he moved to Alaska to work for the National Park Service as an archaeologist. "I had seen snow maybe three times in my entire life," he says. Not knowing any better, Mr. Kardatzke brought his Texas clothes with him, including pants, shirts, underwear, socks, and jackets made of cotton.

"The problem with cotton is that when it gets wet - either from one's own perspiration or from an outside source - it draws the heat away from one's body and transfers the heat to the air around you," he says. Such garments won't keep someone warm when it's 25 below zero F.

Kardatzke quickly traded his cotton jackets for ones made of synthetic fleece or wool. He bought thermal underwear, lined pants, and waterproof wind pants. He got thick boots with felt liners (they made him look two inches taller, too). Finally, he bought a thin pair of gloves, a thick pair of gloves, and big, water-repellent mittens. (Mittens are warmer than gloves because they let the fingers touch. That conserves body heat.) He wore all three layers outside in winter.

Kardatzke, now a program manager at Boston's Museum of Science, learned what early humans discovered thousands of years ago: Staying warm is as important to survival as food.

He also discovered what humans learned centuries ago: Wool is great for keeping one warm.

No one knows who figured out how to shear sheep, spin the fleece into thread or yarn, and weave (or knit) it into woolen garments. But by 1900 BC, wool was big business in Ur, in what is modern-day Iraq. The earliest surviving woolen textile - found in a Danish bog - dates to 1500 BC.

And while synthetic fleece may be lighter and more fashionable today, wool is still used widely. Why? Because wool fibers are kinky.

Wool fibers are naturally wavy. The kinks form tiny air pockets in wool fleece, yarn, thread, and felt (wool fibers compressed into a thick cloth). The air pockets keep the air from moving. Since it can't move, it can't carry heat away from the body. The heat stays in, and the person wearing wool stays warm.

Wool is also coated with lanolin, a fat that repels water. "Sheep don't get wet when standing out in the rain," says David Murray, a coordinator at Boston's Museum of Science, "because they are essentially waterproof." (Much of the lanolin is removed from wool before it's spun into thread and yarn, but some remains. Today's knitters find that the lanolin in wool softens their hands as they work the yarn.)

Wet cotton feels cold and clammy next to the skin. Capillary action draws the water along the surface of cotton fibers, filling all the insulating air spaces with heat-conducting water.

Wool, on the other hand, keeps you warm even when it's wet. While the outside of wool fiber repels water, the inside soaks it up - trapping the moisture in its core. But the air pockets in between the fibers stay empty and dry, so they still hold your body heat.

That's why towels are made of cotton. It's also why you can't dry off very well with a wool sweater.

The Pilgrims knew the importance of wool when they sailed on the Mayflower in 1620, says Christopher Messier. Mr. Messier is lead museum teacher at Plimoth Plantation in Massachusetts, a living history museum.

Pilgrims wore many types of woolen clothing not commonly worn today. The men wore woolen waistcoats over linen shirts with long tails. The shirts were tucked into woolen breeches that extended just below the knee. They pulled on layers of linen and wool stockings. Their leather shoes were low-cut, and the leather soles were covered with little metal studs, called hobnails, for traction.

English women dressed in layers of woolen petticoats, skirtlike garments that came down to their ankles. Women also wore woolen waistcoats lined with linen that buttoned up the front. In bad weather, men and women wore distinctive long coats or cloaks of heavy wool.

Does all that wool sound itchy? Woolen broadcloth could be very soft and fine, Messier assures us. "Frieze" had a looser weave and was coarser. "Kersey" was between the two in texture. Coarse woolen weaves could be made softer by "fulling." The cloth was soaked in vats of stale urine. The process shrank the woolen cloth, making its weave tighter. This thickened the cloth and made it more windproof, too.

Wool is good for staying warm, but fur is even warmer, as the Pilgrims' Wampanoag neighbors knew. Here's what the Wampanoags wore, according to Randy Joseph, education manager of the Wampanoag Indigenous Peoples Program: moccasins of deer or moose hide, with leggings and breechclouts of deerskin. A fur mantle was worn with one shoulder exposed. These mantles, similar to capes, were made from the skins of skunk, raccoon, squirrel, fox, beaver, otter, deer, or moose.

Unlike the fashion today, though, the fur was worn next to the body. The fur trapped tiny pockets of warm air, while the leather outside was windproof. To protect their exposed shoulders, the Wampanoags smeared them with bear grease. They didn't wear any hand or head coverings. It was the same winter dress they had worn for tens of thousands of years. Using furs to stay warm almost certainly dates back to prehistoric times.

Today, wool and fur are still worn by humans living in the coldest climates. But humans are constantly trying to develop synthetic materials that mimic the insulating properties of wool and fur. The main difference between manmade materials and wool is their moisture-absorbing capacity. Wool will absorb more than 12 percent of its weight in moisture, according to Ken Cox, a tech service specialist at 3M, which makes Thinsulate. Synthetic materials only absorb one-tenth of 1 percent. Wool may be warm when it's wet, but it's also a lot heavier then.

Down - tiny goose feathers - has been used as an insulating material in cold-weather gear for a long time. Down-filled blankets (comforters) were popular long before down-filled outerwear became practical and widespread in the 20th century. But down collapses when it gets wet, defeating its insulating ability. Synthetic fibers tend to maintain their "loft" (and therefore their insulating ability) when they get wet.

Thinsulate insulation, introduced in 1979, was the result of more than a decade of research by 3M. Manmade polypropylene, a petroleum-based synthetic polymer, is turned into tiny "microfibers" that are one-tenth the diameter of a human hair. (Polymers are chains of molecules like strings of beads.) They made a kinky, coiled fiber. When these fibers are compacted together, a thin but highly insulating material is formed.

According to the manufacturer, Thinsulate can provide the same insulation as wool or down-filled garments and still be much lighter than either.

"Remember to wear your hat, boots, and mittens!" is a typical "mom" saying.

There is wisdom in dear Mom's words. Much of your body heat escapes from your head. That's because so much skin surface is exposed. Hair, like fur, is the right idea - it traps warm air close to your head - but it's often insufficient.

Wearing a hat stops some of that heat loss. Putting on a hat is like putting a lid on a pot to help it heat up more quickly.

Your hands and feet are the hardest parts of your body to keep warm. That's because when the core of your body - your torso - starts to get cold, less blood flows to your extremities (your hands and feet - not to mention your ears and nose).

So go ahead - enjoy the cold. But listen to your mom, and stay warm!

In 1921, a group of Englishmen became the first Westerners to set foot on the world's tallest and most challenging mountain. To look at them, though, they seemed dressed as though they were going for a walk in London. They were woefully underdressed. They wore tweed jackets (a thick wool fabric) and horseback riding boots. Maybe that's why they only got 22,000 feet up the 29,000-foot peak.

George Leigh Mallory was perhaps the most famous of these first explorers. He was to make two more attempts at the summit. He was much better dressed for his later climbs. (See illustration.) No one knows if Mallory and his climbing partner Andrew Irvine succeeded on Mallory's third try in June 1924, as neither one returned. Chinese climbers following their route found a body, probably that of Irvine, in 1960. A 1999 expedition discovered Mallory's remains at 27,000 feet and buried him on the mountainside.

A camera Mallory borrowed from a fellow climber while on that last attempt has never been found. Though it is unlikely that Mallory and Irvine could have succeeded in reaching the top using the difficult route they chose, no one knows for sure. The summit that Sir Edmund Hillary and Tenzing Norgay reached in 1953 may have been conquered 28 years before.