Wool is self-evident, but what do we mean by synthetics? At their root is something we call the polymer, which is a product of petroleum and a few other chemicals mixed into a cocktail that produces an inherently stable, durable product. It all started around the turn of the century with the invention of PVC (Poly Vinyl Chloride), one of the first polymers to hit the mainstream. From there, production and invention continued at a steady pace until the 1960s and 70s when PolyEster took over young fashion from bell-bottoms to tight “Travolta” pants. The disco was a big gyrating plastics party. In the ’80s and ’90s, synthetics hit mainstream and largely overtook natural fibers, marketed as performance wear. This was when we heard about tech fabrics such as PolyPro, micro-fleece, lycra, perma-loft, spandex for outdoors, and exercise markets. In 2014 synthetics overtook natural fibers in terms of sheer import volume for the United States textile industry.
No industry has driven more innovation in the synthetics category than the Outdoor Industry with the high demands for lightweight, moisture-wicking, insulation, fast dry, and low cost. But let’s remember that in 1953 Edmond Hillary became the first person to Summit Everest, and his clothing was made entirely of wool. So where did wool go, and is it really so inferior?
Experienced outdoor people consider their clothing according to 3 layers. The base layer is directly against the skin, often referred to as long underwear, the mid-layer, a warm insulating layer like a fleece or sweater on top of the base. Finally, the outer layer often in the form of a jacket or shell. Tuning in these 3 layers will keep you warm all day in a winter storm. For this comparison, let's stick to the base and mid-layers as the outer layer will most likely be a type of synthetic shell, where the hydrophobic fibers coupled with a Gore-Tex® coating really excel.
In terms of insulating value, wool and synthetics are comparable. Where they differ is in their treatment of moisture, especially sweat. You should always expect to sweat a bit, and synthetic fiber is designed to move mechanically, through capillary action, the moisture from the skin to the exterior surface, where they depend on evaporation for dissipation. An over-soaked synthetic layer can get cold and clammy. However, they dry extremely quickly. By contrast, a merino wool layer can absorb 30% of its weight and still feel dry to the touch, it maintains its warming properties even while saturated, but it takes longer to dry than the synthetic counterpart.
Mid-layers are typically bulkier and more substantial than your base=layers, where you may be concerned with weight. Pound-for-pound, a synthetic fleece will out insulate a wool layer. When weight is your primary concern, a polyester fleece pullover will be your best choice. However, if you can put up with a wool sweater's weight, wool is more wind resistant, performs better when wet, and will keep you toasty in colder, wetter conditions.
Other deciding factors:
One of wool's more impressive properties is it’s anti-microbial, anti-bacterial properties, meaning it takes an impressive amount of sweat and reuse before it starts to stink. 10 days in a wool base layer, and you will be hard-pressed to detect any odor. However, one day in a synthetic and the sour smells begin to radiate. So if you’re going on a multi-day expedition or want longer between washes, wool is a hands-down leader.
Fire resistance is a factor in outdoor activities. All synthetics are subject to melting, and in most cases, they are outright flammable. Wool, on the other hand, can take the occasional close encounter with heat and fire with little more than a singed hair and a foul burning smell.
Price could be a major factor in your decision-making process. Synthetics came into the mainstream because they could be mass-produced by factories with a flip of the switch. Whereas wool takes a growing cycle to produce the supply, it is subject to weather and other environmental conditions. From a manufacturing perspective, wool less stable and harder to predict, making it more expensive to produce. You will find synthetics at a fraction of the price of a good wool layer.
Synthetic fiber is virtually indestructible; therefore, it is a more durable product over time. You will get a much longer life out of your poly layers than you will your Marino. Marino will slowly lose fibers and thin over time. It is a slow process, so expect many seasons out of your wool layers, but not as many as your tech fabrics.
Washability of wools gets back to a more primitive past of washing with then air drying to avoid felting or shrinking. You may have wondered earlier why anyone would want to go 10 days without a wash well… Around our house, we wait a few weeks between wool washes, then get it all done at once. It really isn’t that bad. If like me, you're not a fan of frequent wash cycles, this could be considered a benefit 😁.
Environmental impact is at the front of my buying decisions. Synthetic fabrics are just plastics pulled into fine threads; they do not biodegrade. Microplastics are saturating the water supply and therefore the food we eat. These plastics' impact on/in our natural resources, critters, food supply, the environment, and bodies is still somewhat unknown. Still, we do know that introducing artificial components to a natural system can be dangerous. The synthetic fibers become water-born simply by washing your clothes, drain out through the wastewater system, yet are too fine to be caught by filters. It is estimated that up to 35% of the Ocean's microplastics originate from fabrics and clothing. Wool, however, came from the earth and returns to the earth naturally. For this reason, we suggest that the price of synthetic is too high and to choose wool where performance is not considerably sacrificed. Please consider contributing to 5Gyres, an organization fighting to understand and counteract the pollution of our oceans https://www.5gyres.org.