Cotton is one of the most common fabrics when it comes to clothing. While it’s perfect for indoors, it’s less than an ideal choice for outdoors. I’ll explain here why that’s the case and what fabrics are much more suitable for a day in the hills.
Cotton kills – Is it true?
“Cotton kills” has become a catchphrase in the hiking community worldwide. As with all clichés, there is some truth to it: Wet cotton doesn’t provide any insulation and can lead to hypothermia in cooler weather.
Although most hypothermia-related deaths of hillwalkers in Scotland happen during the winter months, it doesn’t mean that it never happens at other times of the year. When the conditions are right, and walkers are not prepared for them, hypothermia can also become a problem in spring or summer.
Does this also apply to denim?
Short answer: Yes.
Long answer: Denim is 100% cotton, so the effects of wet jeans can even be more drastic than those of a wet cotton shirt that’s only made from 70% cotton and 30% synthetics. This makes jeans the worst trousers to wear for hillwalking – especially if you don’t carry an extra pair of rain trousers with you.
Plus, they can also be uncomfortable to wear on a very long walk, as they aren’t as stretchy as trousers made of other fabrics, and the continuous friction of the jeans fabric against the insides of the legs can cause chafing.
What makes a great insulator?
The best strategy to decrease the risk of becoming hypothermic when hillwalking is to wear clothes that keep the body warm when wet. For a fabric, this means it needs to have certain functionalities making it an excellent insulator:
- Absorbs no or only little moisture
- Wicks moisture away from the body
- Dries quickly
Cotton doesn’t fulfil any of the criteria above. It absorbs massive amounts of water (either rain or sweat). Thus it doesn’t wick moisture away from the body but keeps it close to it. In addition to that, cotton takes a very long time to dry.
While wearing cotton in dry conditions and not sweating that much, there’s no problem at all: It keeps the body warm and is a good insulator. But once it’s wet, the insulation effect decreases. The wetness of the shirt on the body makes you feel cold quickly – especially when there is wind. So even on a warm summer day, when a cotton shirt is wet from sweat, this can cause a very unpleasant feeling.
What should you wear instead of cotton?
Now we know that cotton is a terrible insulator once wet, so what should you wear instead for hillwalking? There are several possibilities that all have their advantages and disadvantages.
Merino wool
This is personally my favourite fabric for a base layer. Merino wool is a superb insulator suited for summer and winter conditions.
This fabric is highly breathable, which means that on hot days it releases the body’s heat from underneath and regulates the body temperature effectively. On the other hand, when it’s cold, the fabric keeps the heat close to the body, acting as an insulator.
Plain and simple: Merino wool keeps you cool on hot days and warm on cold days.
As with all wool, another advantage is that it’s anti-bacterial and thus doesn’t smell bad as quickly as other fabrics once it has absorbed sweat and the bacteria contained within it. A merino wool shirt doesn’t have to go into the wash after every hillwalk but can be aired out instead to be fresh again. So, it’s enough to wash it after three or four walks or when you notice it smells bad.
Compared to cotton, merino wool wicks away the moisture from the body more effectively. Although the wool absorbs some moisture, most of it is transported to the outside of the shirt, where it will dry quickly in the sun or be absorbed by the fabric of the mid-layer you’re wearing.
The disadvantages of merino wool are that the fabric is not as durable as cotton or microfibre, it’s more expensive and not as soft as other fabrics.
Merino wool at a glance
| Advantages | Disadvantages |
|---|---|
| Optimal regulation of body temperature | Less durable than other fabrics |
| Anti-bacterial: Less smelly | Expensive |
| Great insulator: Wicks most moisture away from the body | Not as soft as other fabrics |
| Dries quickly |
Microfibre
Another excellent alternative to cotton is microfibre, such as polyester or nylon. Unlike merino wool, these are synthetic materials. They feel a bit softer on the skin than wool.
In addition, microfibre dries super-quickly and wicks moisture away from the body better than any other material because it absorbs almost no moisture at all. That’s also why highly water- and windproof jackets are made exclusively of microfibre fabrics.
Depending on the synthetic mix, microfibre clothing can be highly breathable, highly waterproof, or anything in between.
Highly breathable microfibre materials are great as a base layer for summer conditions.
In contrast, a slightly less breathable shirt makes for a good base layer in winter as it traps the heat close to the body. Microfibre clothes are also a lot cheaper than merino wool clothes.
However, polyester and its synthetic siblings also have some drawbacks: They are not anti-bacterial and start to smell very quickly. Therefore, washing them after every hillwalk is a must. Also, people prone to athlete’s foot might not want to choose microfibre socks, as they are a breeding ground for bacteria and fungi.
Furthermore, microfibres lose so-called microplastic fibres whenever they are washed. This leads to microfibre pollution in the drinking water and the oceans, harming humans and animals.
Microfibre at a glance
| Advantages | Disadvantages |
|---|---|
| Highly breathable fabric mixes ideal for hillwalking in summer | Smells bad quickly |
| Superb insulator: Wicks almost all moisture away from the body | Microfibre socks can cause athlete’s foot more quickly |
| Dries super-quickly | Loses microfibers when machine-washed and tumble-dried |
| Less expensive than merino wool |
Should you avoid cotton at all costs?
While it’s best to go for a base layer that doesn’t contain any cotton, a pair of trousers or a mid-layer jacket partly made of cotton are great choices for a lot of situations. As long as the trousers and the mid-layer also contain synthetic materials to make them slightly water-repellent and quick-drying, there’s no concern, and you will stay dry when it drizzles, or a light shower comes in.
If you plan to go out when frequent rain is forecast, it’s best to pack a separate rain jacket and a pair of rain trousers made of pure synthetics. A highly breathable base layer made of merino wool or microfibre will prevent you then from extensive sweating under this plastic armour.
Summing up: Merino wool and microfibre are the best base layer fabrics for hillwalking
We have seen now why cotton is a terrible choice as a base layer for hillwalking: When wet, it loses its insulation, which makes you feel uncomfortable at best, and can speed up hypothermia at worst.
Luckily, there are other fabrics, namely merino wool and microfibre. While the former is a natural product, the latter is synthetic. Both have their advantages and disadvantages, but they are equally good choices when it comes to hillwalking clothes because they don’t have any of the drawbacks that cotton has: They regulate your body temperature, wick away most moisture from your body and dry quickly.
This makes them the ideal choice for base layer clothing – shirts and thermal underwear. For trousers and mid-layers, cotton is acceptable as long as enough synthetics in the mix make the fabric slightly water-repellent and allow it to dry more quickly than pure cotton fabric.