Base Layer Buying Guide

Merino wool is sourced from the Merino sheep and it is an exceptionally good material for base layers. Its wool is very warm, brilliantly breathable and feels soft and comfortable against your skin. The other interesting thing about Merino is that it is naturally anti-bacterial. This means that it will resist odours, even after multiple wears without washing.

Some manufacturers take a synthetic fibre and blend it with a natural. This process is designed to combine the beneficial qualities of both materials. The result is a hardwearing, warm material that is quick drying and breathable. It is then possible to change the ratio of the blend until the quantities of each material are fine-tuned to a specific activity or climate.

Once you know what sort of material suits your needs, you can look at the sort of features you want. So from hot days, to sub-zero mornings, the many ways that base layers keep us comfortable and protected are highlighted below.

One of the most important characteristics of a base layer is its ability to wick away moisture. Like the wick of an oil lamp, this process involves the fibres pulling sweat away from the surface of your skin, and then passing it along its length until it can move away onto the next layer of clothing. This keeps your skin dry and at a regular, comfortable temperature.

As they sit directly against your skin, base layers need to create very little friction and are therefore made from smooth fibres. Additionally, by using ‘flat-lock seams’ some manufacturers give their stitches a very low profile. Some base layers also avoid having seams over the shoulders to minimise the friction from rucksack straps, or against softer skin such as under the flanks.

When working hard in cold conditions a gentle through-flow of air can be appreciated. Zip necks are one way to customise the level of ventilation, as are thinner pieces of perforated material that cover the underarms or along the spine. The purpose of these aerating features is to keep your temperate consistent, rather than getting hot and sweaty during activity and damp and chilled when stationary.

Breathability is different to ventilation, and refers to the ability of a material to allow sweat vapour to pass through the fibres. If a material was not breathable then every molecule of water vapour expelled from your skin would be trapped, like condensation against a window. Synthetic materials are very good at breathing efficiently as they absorb little water and dry quickly.

Base layers are made in a variety of densities and thicknesses. Generally speaking the colder the conditions the warmer and thicker you will need the layer; however the type of activity is also fundamental to this requirement. If you are going to be working really hard in the extreme cold you may actually need a thinner layer than if you are stationary in milder conditions.

Base layers are like a stretchy second skin, and like your skin it should follow the contours of your body and move with you through a range of actions. It’s good to find a balance between it being baggy and feeling restrictive. If it is too tight the seams will rub and the fibres will be opened apart, too baggy and all that warm air will easily escape.

Although base layers for the torso are the most common, the materials used and the theory involved is the same all over the body. For example, the legs work very hard and take up a large surface area, so keeping them warm, dry and comfortable makes good sense. Gloves, headwear and of course the all-important super breathable, thermal pants; everywhere can enjoy the comfort of a base layer.