So far, almost all base layer recommendations have been for Merino Wool. Last fall I wore Smart Wool on an October backpack hunt in Idaho and was really impressed with the comfort and performance. Since then I have been doing a lot of research on Merino wool.
Originally the term merino specifically regarded the wool of Merino sheep reared in Spain. However, due to the equivalent quality of Australian and New Zealand wool it now has a much broader meaning. Merino sheep have the finest and softest wool of any sheep. Merino’s wool is finely crimped and soft with Staples 2.5 – 4 inches long and less than 24 micron (µm) in diameter. Basic Merino types include: strong (broad) wool 23 – 24.5 µm, medium wool is 19.6 – 22.9 µm, fine 18.6 – 19.5 µm, superfine 15 – 18.5 µm and ultra fine 11.5 – 15 µm. Ultra fine wool is suitable for blending with other fibers such as silk and cashmere.
High-quality merino performs in cold and warm weather. There is a lot written about the advantages of wool for cold weather, however warm weather is where I was most surprised. Wool naturally pulls water away from your skin and into the fibers up to 1/3 it’s weight. In warm weather this moisture in the fibers causes an evaporative effect that actually cools the skin.
The key to Merino is understanding what you are buying. I recommend only superfine merino for next to skin. Superfine Merino 15 – 18.5 micron (µm) has no itch and is very soft and comfortable. I have heard complaints of Merino being itchy and uncomfortable. If you put Medium Merino 19.6 – 22.9 µm next to your skin you may feel a slight itch due to the larger fibers and more importantly larger scales on the fibers that cause the itch. I highly recommend next to skin layers with 17.5(µm) fabrics. 18.5(µm) fibers are more common for base layers due to the higher expense of 17.5(µm) fibers. From my testing it is worth the extra expense for 17.5 (µm) merino.
Read the contents labels carefully and buy only 100% merino wool. Some fabrics include poly blends and lycra. Lycra attracts water and will wear out over time.
MERINO PERFORMANCE HIGHLIGHTS
- Merino is excellent at regulating body temperature, especially when worn against the skin. It provides some warmth, without overheating the wearer. The fabric draws sweat away from the skin and is slightly moisture repellent (keratin fibers are hydrophobic at one end and hydrophillic at the other), allowing the wearer to avoid the feeling of wetness.
- Merino can absorb moisture up to 1/3 its weight. Unlike cotton, it retains warmth when wet because it pulls the moisture away from your skin.
- Merino is naturally anti-bacterial resistant, which causes the fabric to resist odor caused by sweating. This is a huge advantage compared to synthetic fabrics and ideal for extended backcountry hunts.
- Merino is incredibly soft, due to finer fibers and smaller scales which eliminates the itch associated with regular wool.
- Merino has an excellent warmth-to-weight ratio compared to synthetics and to other wools, in part because the smaller fibers have microscopic cortexes of dead air, trapping body heat similar to the way a sleeping bag warms its occupant.
During my research I have cultivated a relationship with the leading Merino supplier in New Zealand. They work with several high-end Outdoor brands and offer some absolutely amazing fabrics. We are working on the development a couple of new fabrics for KUIU.
It would be helpful to better understand what weight and style base layers you prefer? My preference is a light weight 150-185 g/m2 next-to-skin and an expedition weight 200-240 g/m2 as the next layer in the system. I prefer both of these shirts as a Zip-T to ventilate during a climb.
Thanks for the input and help.