When it gets warm on the trail and you begin to sweat you need fabrics that wick away perspiration and cool the skin.
Great Walks has prepared this handy guide to help consumers understand which textiles, both natural and synthetic, to rely on during a warm day on the trail.
Natural Fibres
Many avid bushwalkers insist that one can’t go past natural fibres to help shield us from the elements, and indeed there is much to recommend them. First and foremost, they are far more sustainable and produce less post-manufacture pollution than synthetics, although they generally wear out faster. But do they perform as well in the heat?
Cotton – Let’s get this out of the way first: pure cotton is almost never a suitable material for outdoor gear. It’s absorbs water, staying wet and heavy, and when the temperature drops i.e. at night, it cools rapidly, sucking heat from the body. Plus, unless it is organically-grown it requires an unholy amount of water to produce.
Merino – Once popular, then forgotten, and now heralded as a super-fabric, finely-spun merino wool is a much better choice. It regulates the wearer’s temperature, heating or cooling when necessary, is highly UV resistant, wicks reasonably well and is super comfy. It doesn’t dry as fast as synthetics will and it can be pricey, but merino remains many people’s trekking layer of choice.
Bamboo – Bamboo clothes? No, we’re not talking about some wooden armour-clad samurai. Pulped bamboo can actually be broken down with an enzyme (called ‘retting’), washed and a fibre extracted which can be woven into cloth. At this point it becomes a textile called Rayon (which can also be made from many types of wood pulp) which is surprisingly soft and has all the right properties - wicking, odour-repelling, sustainability and sun protection, and when blended with elastane is stretchy enough for any activity. The downside? It also doesn’t dry as fast as the man-made options.
Silk – Less popular than other fabrics for outdoor use, partially due to its expense, silk actually performs very well as an insulator and is famously luxurious against the skin. Unfortunately spun silk does not have good enough abrasion resistance to be used in outdoor clothing without being blended with another fabric, usually nylon or cotton. Lastly, it is quite absorbent and doesn’t react well to sweat or UV light.
Synthetic Fibres
Synthetic fabrics are manufactured from oil-based materials, usually plastics, and are specifically engineered to perform a range of tasks by clever textile scientists. Because of this they are excellent at what they do and are often stronger than natural fibres. However, there are some features of the latter that have so far not been perfectly replicated in synthetics, most notably odour control. Then there is the pollution issue, with cast-off and laundered clothing breaking down into micro-plastics and filling our oceans, and sea life, with toxins.
Nylon – Maybe the most popular choice for outdoor clothing, especially in collared shirts and trousers, nylon was the first synthetic fibre to be invented. Although very strong, wrinkle- and shrink-free and able to wick moisture very well, it does absorb 3-4% water. While this marginally increases drying time, in summer heat it can help cool the body as the moisture evaporates. Not all nylon fabrics perform the same though – much design goes into the shape of the fibres and how they are woven in order to move moisture efficiently.
Polyester – This fabric shares many of the properties of nylon but, being more hydrophobic, capillary action through woven polyester moves sweat away from the skin faster, and hence it is a more popular choice for standalone athletic layers such as t-shirts. On the other hand, polyester is not as strong as nylon and does absorb a certain amount of oil, which is why it holds odour for longer and is often criticised for being particularly stinky. You will often see poly fabrics blended with natural materials such as silver salts, Xylitol or Cocona to improve their odour-resistance. Most outdoor brands have their own proprietary polyester fabric or use a third party one, the most famous of which is Coolmax.
Polypropylene – Even more hydrophobic than polyester, polypropylene doesn’t absorb water at all and is thus even quicker drying. However polypro is less resistant to UV and will not last long as an outer fabric. For this reason it is more usually used as a base layer, for which it is an excellent choice. Think of it as an artificial version of silk.
Blends
Of course, many manufacturers experiment with combinations of natural and synthetic fibres in an attempt to achieve the benefits of both. Here are some examples:
Elastane is often blended with both natural and synthetic fibres to add some stretch, a very useful property in outdoor apparel.
Icebreaker recently changed their 100% merino wool formula to Corespun technology, wherein merino is wrapped around a core of nylon thread, vastly increasing the strength of the garment. No more tiny holes!
UK brand Rab have developed MeCo, a blend of 65% merino and 35% Cocona, derived from coconut husks. The huge surface area of the latter component offers increased wicking and quicker drying capabilities.
Clothing brand Lé Bent use a blend of 66.5% bamboo, 30.5% merino and 3% elastane for a perfect balance of four-way stretch, anti-odour and softness on the skin.
Words_Dan Slater