Keeping Warm With 'Frozen Smoke'

Jan. 11, 2005 — -- Jake Steingraeber spends hours at a time standing still in subzero temperatures, but thanks to technology borrowed from space and slipped into his boots, his toes stay warm.

"I was ice fishing and on the ice for three days and my feet never got cold," said Steingraeber, a hunter and fisherman from Wisconsin.

A superlight solid called aerogel, which has been used to insulate rovers rolling around Mars and to cushion the impact of comet dust penetrating a speeding spacecraft, has recently been tapped by those in the business of keeping people warm.

While parkas and bootliners made of the so-called frozen smoke remain pricey, some see the day when aerogel-insulated gear will be as pervasive and affordable as insulating products such as Thinsulate, Hollofil and down.

Burlington, Vt.-based Burton Snowboards placed more than 1,000 parkas with aerogel lining on the market last year for $550 each. The line sold out and this coming fall the company plans to unveil a $250 version that features patches of the insulating gel. Meanwhile, Shock Doctor, a Plymouth, Minn.-based sports gear company, has started selling shoe and boot liners with the material for insulation against heat and cold.

Micropores Create Ideal Insulator

Aerogel's unique advantage as an insulator is a little bit of it goes a long way. Ed Hogan, marketing manager of Aspen Aerogels in Northborough, Mass., says the insulation value of a half-inch of aerogel is equivalent to an inch of Thermalight or Thinsulate or two inches of down or standard fiberfill. This is thanks to the tiny air pockets contained within the gel, which measure about 1/3000th the diameter of a human hair. The nanopores are extremely effective at blocking heat transfer.

"A couple years ago Hugo Boss made elite jackets from the material," he said. "They discontinued them because they were so warm -- they were unzipping them in Antarctica. The trick is to find the right balance of thickness."

While the silicon-based solid is fairly new to commercial markets, it has been tinkered with by those in the science community for decades.

The porous substance was first discovered in 1931 by California scientist Samuel Kistler. Kistler showed how the substance could be created by drying gels under supercritical conditions. The process leaves behind a network of interconnected silica material (the same material that glass is made from) that is 99.8 percent air and provides insulation that is two to 10 times better than existing insulations.

NASA scientists like Peter Tsou at the Jet Propulsion Laboratory in Pasadena, Calif., have since rediscovered the unique gel and used it in a variety of space applications. Tsou helped create a version of the material to collect comet dust particles traveling up to six times the speed of a rifle bullet as part of the Stardust mission. The gel has been used to insulate the electronics box on the Mars Pathfinder Sojourner rover, which explored the planet in 1997. Others are developing Mars parkas that could keep astronauts warm at temperatures as low as minus 150 degrees Fahrenheit.

When it comes to commercial applications, Tsou argues the aerogel's greatest commercial potential lies in window insulation.

"Aerogel is warm, but it's not ideal for things that are constantly moving -- you break it up," he said. "The Holy Grail for aerogel is window insulation. A single candle could be enough to keep a room warm if the windows were insulated with it."

Warm Windows and Pipes

Tsou admits, however, that a couple hurdles remain. First the cost is still high. He calculates that while a 1-by-1-foot piece of glass may go for about $1, the same sized piece of aerogel could run as high as $5,000.

The other potential problem is aerogel's transparency -- or lack thereof.

"Looking through aerogel it is smokey," he said. "There is some disturbance."

Tackle those issues and Tsou claims there's no better application. The Boston-based Cabot Corp., has actually started developing thermal windows and skylights insulated by aerogel in particle form.

In the meantime, Aspen Aerogels is banking on marketing its blanket form of the insulator for outdoor gear, and as pipeline insulation.

Steingraeber, who recently spent four hours straight standing on the metal grate of a hunting tree stand, is already sold on using the space-age gel to keep warm.

"It turned from freezing rain to snow so my clothing was frozen stiff, but my feet were warm," he said.