If you’ve ever been on a winter camp with the Boy Scouts, or are the parent of a Boy Scout that has gone on winter camp outs, you’ve probably witnessed the phenomenon of “The Melted Shoe Soles”.
This happens when the person wearing them has wet shoes/boots and cold feet and puts them close to the fire.
But why don’t they feel the heat before their shoes melt?
Insulation is an inactive material. It merely blocks or inhibits the transfer of heat from one area to another. This can be done through the mass of the insulation such as a stone wall, or through the stabilization of air pockets between the insulation material, such as down, polyester batting, and foams. The more effective the material and its configuration, the more effectively the transfer of heat energy is blocked.
So, back to the shoes. The soles of the shoes are thick enough that because of their mass they are fairly effective at slowing the heat that reaches the feet. So, before you feel the heat in the soles of your feet, the soles of your shoes have reached a temperature hot enough to start melting the rubber and plastic.
I used to be in the cold weather clothing business, and the outer fabrics that we used were made of polyester, because synthetics are often better than natural fibers, especially cotton. Often the concern about melting the fabric and it catching fire would come up, especially about children wearing synthetic fabrics.
The basic reason for this concern was that children (and many adults) are drawn toward a camp fire. There is something wonderful about the heat from a campfire in the cold. However, like the shoes, if you get closer and closer to a fire because you cannot feel the heat, that means that your insulation is working (or all the water in your clothing is absorbing the heat)! Beware! Your jacket and pants could end up like the soles of the shoes, but it could also result in injury from melted materials and the heat from burning clothing.
One way of preventing this from happening, especially with children, is to dress in an uninsulated cotton outer shell (I usually wear one myself) over the synthetic winter clothing.
What will happen is that the outer cotton shell will become wet, and when close enough to the fire, it will begin to steam (this is the first warning sign that they may be too close to the fire). When it dries out, if the heat is still too great, it will begin to brown (this is the second warning sign that they may be too close to the fire).
There is a saying, “In winter, cotton kills.” And when used as the primary material in your winter clothing, it certainly has that potential. However, I have found that this particular application of cotton over the synthetic winter clothing works very well at preventing accidental injury through unintended exposure to excessive heat. It will also help save your synthetic clothing!
Stay dry, stay warm!