When we started getting inquiries from Canadian and US military for Brynje mesh base layer it certainly made sense. Years ago, the Norwegian government had done studies which showed conclusively that mesh base layer garments performed significantly better than solid knits and thus they have been issuing their troops the Brynje mesh underwear for decades. Guess who trains the US and Canadian forces that travel to the extremes of the planet? Yup, the Norwegians.
Recently Brynje introduced a Merino wool version of their now famous mesh (famous for the first ascent of Everest in 1953). Merino wool has become extremely popular as a material for base layers, including socks. This is because, as a fiber, Merino wool does not itch, it feels warm when wet and it tends not to harbor odors. So, what could be better than Merino wool mesh?
Back in the 1950’s a new miracle yarn was developed that had dramatically improved qualities for wicking moisture away from the body during high exertion and perspiration. It was polypropylene. Companies like Lifa, Helly Hanson and Patagonia started producing underwear made of “polypro” in the seventies and eighties. It worked well but had an unfortunate deficiency, after numerous washings the polypropylene would start to harbored odors. Not a pleasant characteristic. However, the Schoeller company has now developed a new polypropylene yarn called Polycolon® with much improved odor attenuation properties. Additionally, a mesh undergarment allows the moisture to travel through the fabric in vapor form rather than being wicked as a liquid through capillary action. This means that there is much less bacteria being trapped on the fibers and much less material contact with the skin.
There are three primary considerations for effect base layer clothing: weight, moisture management and warmth. Here are some statistics for different fibers used in these garments
Dry Weight:
- Polypropylene 09 gr/cm3
- Nylon 14 gr/cm3
- Wool 32 gr/cm3
- Polyester 38 gr/cm3
- Cotton 50 gr/cm3
Moisture Absorption as a % of Dry Weight:
- Polypropylene 5%
- Polyester 40%
- Nylon 450%
- Cotton 800%
- Wool 1,600%
Thermal Insulation Capacity (the lower the number the better the insulation):
- Air 0
- Polypropylene 0
- Polyester 0
- Wool 3
- Cotton 3
It is clear from the statistics above that polypropylene is a lighter, drier and warmer fiber than nylon, polyester, cotton or wool. However, durability is another important factor. As an environmental issue, the longer a garment lasts the less impact its manufacture has on the environment (and better value to the user). Synthetic fibers can last four to five times longer than 100% Merino wool. This is why Merino wool is often blended with polyester fibers to increase durability.
Another environmental issue is renewable wool production vs. non-renewable petroleum-based production. While there are wool producers that are excellent stewards of the planet, the fact is sheep produce methane, require substantial quantities of water and can tend to over grazing in high production operations. Additionally, there is the processing of the wool to remove some of the lanolin to allow the yarn to be died. Synthetic yarns, by contrast, while not renewable, use far less petroleum by weight than driving your car. A Brynje short sleeve mesh top weighs only 110 gr. while a gallon of gasoline weighs 6.3 lbs. I think you could make the case that this is an excellent use of petroleum since it is used to fabricate a non-disposable item. The polypropylene fiber also accepts color with very little processing.
So, if the objectives for selecting your base layer are light weight, warmth and moisture management it’s clear that a mesh base layer garment made from polypropylene simply will outperform all other options. There is very strong science to document this claim. So if you haven’t tried it, you should put it to the test. You’ll be amazed.