A New Insulation Technique. The difficulty of insulating the body against cold by use of woollen or down garments has always been that, as the insulating medium got damp either from body moisture or from outside moisture, its insulating efficiency was greatly reduced, and the moisture itself absorbed a great many calories of body heat. When an attempt is made to repel outside moisture by use of rubber outer garments, the difficulty is often compounded by condensation of body moisture inside to a degree greater than the outside moisture repelled. At times it seems that there is simply no way to keep the insulation dry.
The Army has developed and tested a simple solution to this problem. The idea is to use two vapor barrier layers, one on the outside of the insulation to keep outside moisture out, and one next to the skin to keep body moisture in. Thus the insulation stays bone dry, and socks and insoles worn days at a time are as dry and fluffy when removed as when first put on. For this information, I am indebted to Dr. Paul Siple.
For the past year and a half experiments have been going on in an attempt to find practical ways and means of utilizing this technique with ordinary mountain-climbing equipment. Since the body can usually take care of itself, the experiments have been confined, for the time being, to the hands and feet. For the feet, two very thin plastic bags were used. Because the plastic is rather uncomfortable right next to the skin, the first layer is a very lightweight women’s nylon anklet sock. Then comes the first plastic bag, then the regular heavy wool sock (or socks and insole, if necessary), then the second plastic bag, and last the boot. The inner nylon sock of course becomes soaking wet, but being thin and of nylon it is very easily dried out overnight. The plastic used for the bags is so thin and slippery that this combination can usually be worn with no change in boot size. Although the bags must be folded and bunched up to fit the foot, no discomfort, even for people with tender feet, has been experienced, owing again to the thinness and slipperiness of the plastic. The only difficulties experienced to date have been that the foot may work its way through the seam of the outer bag, and the inner bag work down under the foot—which is not uncomfortable, but destroys the inner protection. No doubt the seam-splitting can be overcome by improved heat sealing methods. The creeping can be overcome by wearing eight- inch-high boots; rolling the tops of both bags and socks down to the boot top and pinning them all together; or eliminating the inner nylon sock and allowing the plastic to stick itself to the skin.
In winter, at temperatures as low as 20° below zero F., the advantages of this technique are easily appreciated. After skiing four and a half miles, one can stand around for 45 minutes without getting cold feet or hands. Of course, it must be remembered that, no matter how good the insulation on hands and feet, they will not be warm if the body itself is so chilled that it can not spare enough blood to circulate heat to the extremities. In summer climbing the advantages are worth while only for snow or glacier work, in which, after a day of walking around in slush and melting ice, the feet can become thoroughly chilled with only the ordinary protection. With this method they stay comfortably warm. Of course, anyone who finds wet socks uncomfortable can use the method regardless of temperature.
The use of this technique with standard mitten shells and liners is slightly more complicated, owing to the necessity of occasionally removing the mittens. It proved very discouraging to try to manage shells, two plastic mitts, two liners and an inner absorbent mitt. The shells, outer plastic mitt and two liners were therefore pinned together at the cuff, making one unit; the absorbent mitt was discarded, and the inner plastic mitt pulled on next to the skin, after which it was very easy to slip into the rest. For most purposes the plastic mitt need never be removed from the hand when the mitts are removed because it sticks in place and is thin enough not to hinder the sense of touch.
This technique is still in only its first stages of usefulness, but present results are so promising that it can already be used to advantage in preventing discomfort and frostbite in exchange for a little practice in mastering its use. Anyone interested in trying it can write to me for more information or just take it from here. In either case, results and improvements will be of interest.
[It should be noted that the U.S. Army considers this process to be still in the experimental stages, and that it does not at present recommend the technique here described.—Ed.]