COLD INJURIES - Medicine for Mountaineering and Other Wilderness Activities - page 393

water,whichmakesthefabricconsiderablyheavier.Totallydryingthiscorerequiresalarge
amount of heat—generally extracted from the wearer's body.
Synthetic fabrics have largely replaced wool. Pile fabrics, introduced in the 1970s, are
lighter and are hydrophobic. However, they tend to loose their pile and to pill badly with
wear and laundering, so they have largely been replaced by fleece.
Fleeceisasimilarpolyesterfabric,butwithstifferfibersthanpileandsuperiorqualities.
It is produced in different thicknesses: microfleece for underwear and 100, 200, and 300
weightsforoutergarments.Thismaterialbreatheswellandislightweight,durable,andfast
drying. It is easy to cut and sew and has largely replaced pile as a fabric for outdoor cloth-
ing.
Goose downis the best available insulating material forits weight—when it is dry.True
down is the philoplume of geese or ducks and historically was handpicked from those an-
imals, but that material is no longer available. Down now comes from killed animals and
iscomposed oflessmature plumes that donotloftaswell. However,downgarments drape
well, do not constrict movement, loft after compression, and are comfortable. When wet,
down mats together and loses most of its insulating properties. However, when precipita-
tion is in the form of dry snow, which is typical of high altitudes, down is the insulating
material of choice.
Synthetic fibers can provide insulation similar to down and retain their insulating prop-
erties when wet. Although various materials have been tried, manufacturers currently are
using a blend of three different deniers (thicknesses) to gain high loft. (Primaloft® and
Lightloft are the trade names of two down replacements.) The disadvantages of such ma-
terials are their greater weight (about 50 percent heavier than down) and their bulk or lack
of compressibility.
Mat materials are extruded, densely packed fine fibers. Because the fibers are so thin,
theyslightlylimitradiantheatlossbutlosethisadvantagewhenlaundered.Thesematerials
resist compression and do not drape well. (Thinsulate® is the dominant brand of this type
of fabric, the use of which is limited largely to ski clothing.)
Outer Shell
The outer shell must be windproof to protect the insulating qualities of the underlying
clothing. Tightly woven fabrics made of synthetic fibers are most commonly used. The
shellusuallyalsomustbewaterrepellent.Theidealfabricthatwouldallowallwatervapor
to pass through freely but keep out all liquid water has yet to be developed. The best avail-
able fabrics are laminates such as Gore-Tex® and urethane-coated materials, which have
small poresclose enoughtogether toresist penetration byliquid water butlargeenoughfor
mostwatervaportopassthrough.Soilinglimits thefunctionality ofthesefabrics,although
the layer with the perforations is now protected by overlying layers that protect them from
body oils.