Getting your base-layer clothing correct, is the difference between staying warm and comfortable, and being cold and wet. Base layer's are typically thin layers of clothing that come in direct contact with the skin. The idea behind wearing base layers, is they help to maintaining the right body temperature whilst at the same time help to remove sweat away from the skin. If you remove any moisture away from the skin, you will in turn stop getting cold.
Typically base layer's refer to both tops and bottoms with the hiker wearing a set of base-layer clothing, on-top of which you would put wind proof clothing such as fleece jumper and on top of that water-proof clothing such as a waterproof jacket.
Three Main Types of Base Layers
There are 3 main types of base layers; synthetic base layers, merino wool base layers and bamboo base layers. Cotton generally not used for base layers as the fabric tends to soak up sweat from the body, but unlike other materials, does not expel the moisture thus causing the heat to be drawn out of body.
The base layer is one of three layers hikers tend to wear on a hike. The other two are mid-layer and outerwear. If you are taking part in a highly active hike, you may consider doing away with a mid layer and wearing two base layers instead. Preferably two of the above options. For example a merino wool layer on top of a synthetic layer.
Synthetic Base Layers
Synthetic base layers are most common and for good reasons. First, they are the probably the cheapest option of the three. Second, they are arguably the best at keeping your skin dry and ventilated. Third, they dry quickly. So even if moisture does get through, you find it will get back to its normal state a lot quicker than a merino wool based layer. Fourth, synthetic base layers are the lightest option of the three. You may not want to wear them in extra cold conditions, but they are perfect for wearing in either hot weather or during highly active pursuits.
Merino Wool Base Layers
A Merino Wool based layer is the perfect option for cold weather. The wool has air pockets that act as ventilation and fibres to retain the heat. Experts claim they keep you warm in temperatures of up to -20 degrees, and even if the merino wool base layer somehow gets wet. That is why you will often see people wearing merino base layers whilst out skiing.
They have only two disadvantages. First, they cost a lot more than synthetics, particularly if they are handmade made from pure wool – and they would be at the top end of the market. Second they don't absorb moisture as well as a synthetic base layer, meaning your skin could get very sweaty during any vigorous exercise.
Bamboo Base Layers
Bamboo base layers are made from a combination of bamboo extracts and other fibres, particularly cotton. They are a relatively modern invention and are often seen as alternative to people who find wool irritates their skin. Like merino wool layers they are good at retaining heat. Unlike their rival, however, they don't fray and you can expect a bamboo base layer to last you a long time. If you take into consideration that a bamboo base layer is cheaper than a merino wool base layer than that is a lot of money you could be saving. Unfortunately bamboo base layers are not yet as readily available as the other two base layers.
Thickness Vs Warmth
Once you've chosen the material for your base layer, the next choice you need to make is the thickness of your base-layer. Generally there are three different thicknesses; Light-Weight, Mid-Weight and Heavy-Weight. Generally base-layer insulation is measured in g/m² with lightweight baselayers in the region of 150g/m², midweight between 200-250g/m², and heavyweight can be up to 400g/m².
Whilst the choice does depend on how many base-layers you wear (personally, i prefer two thinner base-layers, rather than one thicker layer), general you'll need the following weights depending on the type of sports you're going to be doing.
- Spring/Summer Hiking - Lightweight
- Winter Hiking - Lightweight or Mid-weight
- Overnight Camping - Mid-Weight
- Low Level Snow Covered Hiking - Mid-Weight or Heavy-Weight
- Mountaineering or Very Cold Weather - Heavyweight