Omnitherm makes an incredible range of temperatures comfortable: the same
shirt and pants that keep you warm at 20 degrees below zero will also be comfortable
at 60 degrees above zero. This is possible with a minor change in the layer you put
The layer you choose depends on a variety of personal factors: metabolism, physical
condition, style of hunting, acclimatization, and general health. The under layer that
is right for you may not be for the guy in the next bunk.
The under layer fabrics that have proven best for use with Omnitherm gear are silk,
medium weight and expedition weight synthetics, and a wool sweater.
Vapor Regulation Barrier:
Silk is all you need under Omnitherm when conditions are mild and
temperatures are above freezing. No fabric feels better against your skin. Silk
regulates moisture without adding insulation. That means that when you sweat,
silk keeps moisture on your skin to cool you. It dries quickly when you cool off,
and stays amazingly odor-free. Put your silks over your expedition weight synthetic
when conditions are cold and windy.
When it's cold, synthetic fabrics work the best. Synthetic fibers do not absorb
moisture so these fabrics are easy to keep dry. Omnitherm's ability to
regulate moisture keeps them even drier and greatly enhances their insulation. Thicker
fabrics (expedition weight) trap more air and so add more insulation.
Polypropylene or Polyester? Under a microscope they look the same and their performance
is similar. However, polyester fibers have a much higher melting point -- they can take
hot wash water and a hot dryer where polypropylene cannot. Since synthetic fibers do not
absorb water, the hot water wash helps to get them cleaner and to remove odors.
In extreme cold, add a wool sweater over your expedition weight polys for more loft.
Omnitherm is extremely weather tight, so a waterproof storm shell is only
required in heavy sustained rain or high winds.