Last time I covered the basic rules for surviving fieldwork in the cold. This time I will talk specifically about the layers that make up a versatile cold weather clothing system.
No cotton, remember that? Polypropylene (e.g. Helly Hansen ‘Lifa’) or merino wool (e.g. Icebreaker) base layers are ideal. You want it close fitting so that it wicks moisture (sweat) away from your skin. A long sleeve top and long-johns (aka ‘thermal legs’) are ideal and form your first line of defence against the cold.
A lightweight fleece jumper is ideal, with a good deep neck zip for ventilation. A serious woollen jumper (like a Shetland or an Icelandic) is a good alternative, but will be more expensive. Fleece is hard-wearing, breathable and cheap. It can also keep you warm even when it is damp. What it is not, however, is windproof (usually, there are fleeces with a membrane which are). In extremely cold conditions I add a fleece vest (sleeveless jacket) over the jumper, so in effect, I have two mid-layers.
Over your mid-layer, especially in areas exposed to the wind, a windproof but breathable layer is needed (don’t confuse this with a waterproof layer). Ideally this will take the form of a zip-fronted jacket (which is easy to ventilate) with a hood and pockets (for storing, hats, gloves etc). A windproof provides vital protection from the wind (which standard fleece jackets do not), and importantly breathes. A so-called ‘soft shell’ jacket is ideal here (using a breathable but windproof fabric like ‘Polartec Windbloc’). These are particularly good because they can also shrug off light showers. In sub-zero conditions they can also act as an outer shell, since they can shrug off snow even better.
The term ‘soft shell’ it was coined by the clothing company Patagonia, although the concept was not new. The best have a hood because if it rains and you don’t have a hood you’ll just reach for your waterproof jacket. In warmer conditions, or when I am working hard, I wear a soft shell jacket straight over my base-layer. If I stop working (e.g. stop carrying that survey kit up the hill), I add a mid-layer underneath the jacket. This means that you always have an accessible full font zip for ventilation and a hood if it gets colder or a light shower comes on.
For the legs
In very cold conditions fleece salopettes (‘bib and brace’ style trousers) which eliminate that gap in clothing that can occur at the waist, are perfect, as are insulated ‘ski pants’. If it is not so cold, then a pair of soft shell trousers (or just any non-cotton walking trousers) over your thermal legs may be adequate.
Waterproofs (‘Hard Shell’)
A jacket with hood and a pair of trousers (over-trousers) made of a waterproof, but breathable fabric (see discussion below). If you get wet, you will get cold. Most hypothermia fatalities in the mountains have wet clothing (they are also exhausted and have run out of food). You should not wear your waterproof unless it is raining, however. The reason is that, whatever the manufacturer claims about breathability, you will build up moisture inside the garment, especially if you exercise, and this will reduce the insulation properties of the garments beneath. You will end up cold and clammy.
If you add a waterproof layer (because it has just started chucking it down), but keep up the same level of exercise, you will quickly overheat, sweat, become damp and ultimately get cold. So always strip off a layer before you don a hard shell, unless you are stopping for a break.
If you don’t understand what the deal is with waterproof/breathable fabrics, here is a brief primer. As with a lot of products, it was a discovery, not an invention. An engineer was experimenting with PTFE (better known by the trade name ‘Teflon’ – the non-stick pan stuff) and realised that expanded PTFE (ePTFE) was an extremely thin membrane full of microscopic holes of a size that were too small to allow liquid water through, but big enough to allow water vapour out. It was delicate, so it had to be sandwiched between an outer (face) fabric and an inner (liner) fabric to creating a three-layer waterproof/breathable cloth. First generation Gore-Tex was very expensive and the membrane got clogged resulting in a loss of breathability and (in some jackets at least) a rather special smell. Modern Gore-Tex is really excellent, but there are alternatives (e.g. eVent, H2No, Neoshell, Omnidry, NanoPro and more) some of which may suit you/your fieldwork activities better, but that topic is a whole other blog.
Insulation (for very cold conditions)
If it is very cold, put a serious insulating layer over your double mid-layer (or even over a softshell jacket). The most popular are down-filled ‘duvet’ jackets (e.g. Mountain Equipment, Rab, The North Face). These are largely designed for mountaineering and provide the greatest warmth for weight of any clothing. Drawbacks are that they are not cheap and MUST be kept dry (at all costs). An alternative is a jacket insulated with man-made fibre like ‘Primaloft’. These are not generally as warm, but do not lose all their insulating properties if they get wet and are generally a bit cheaper to buy.
A fleece-lined merino wool beanie is my choice (warm, but not itchy on the scalp), but basically whatever works for you. In really cold conditions add another hat and/or pull up your hood. Whatever you have been told about the huge percentage of your body heat lost through your head, it was wrong. This ‘fact’ was based on flawed research conducted by the US military in the 1950s. Essentially, if your core is warm, a lightweight hat may be sufficient, if it covers the ears and if the wind-chill is not too great.
In very cold conditions wear a thin pair of gloves (e.g. wool or fleece) inside a thicker pair of mitts (e.g. fleece lined) with a water repellent outer. Take the mitts off to manipulate equipment, but leave the gloves on. Cold hands are painful to warm up again.
Neck gaiter, scarf or ’Buff’
Seal the gap at the neck. ‘Buffs’ are a very versatile tube of material than can be used as a scarf or hat or balaclava (warning, you may look a bit odd). ‘Polar’ buffs have a lower half composed of fleece and I often use one these.
Wool-based socks are generally best. How thick depends on the footwear. Lightweight boots need lightweight socks, heavy boots, heavy socks. When working in caves I wear ‘wet socks’ (socks made out of wet suit material – usually 3 mm neoprene) underneath thick wool socks, because you know you will get wet feet. The wet socks trap a layer of water next to your feet which warms up. Normal socks allow water to circulate constantly meaning your body heat just flows away.
May well be dictated by the terrain. You might need walking boots or mountaineering boots capable of taking crampons (e.g. for glacier work). Gaiters seal the deal by keeping out water or snow. Wellies might be the ticket if you are working in wetlands or in excavations where water collects or when in caves (see above).
If you lace up your boots up too tight you will reduce blood circulation and get cold feet. Crampon straps can have the same effect and these horrible metal spikes also conduct heat out of your boots as well.
Right, now you know it, so get out there!