Ace Of Base...

What do they do? The main purpose of a modern baselayer is to shift moisture away from your skin and towards the outside world where it can be dissipated keeping you dry. Without a good baselayer, there's little point in wearing an expensive breathable outer shell because the moisture your produce as sweat will simply sit close to your skin and chill you. That's why cotton tee-shirts are a total waste of outdoor space, except in very hot, dry climates and why you should invest in a decent baselayer.

How do they work? They start off by using synthetic fibres which don't absorb moisture as readily as natural fibres, which are treated with chemicals designed to transport water outwards and spread it across the surface of the fabric so it evaporates more quickly. Some treatments are just add-ons, others are chemically bonded to the fibres so they won't wear out.

Dual Construction A more recent addition is the use of fabrics woven to have inherent qualities, for example, Polartec's impressive PowerDry fabric uses an inner fabric which has a physical structure designed to draw moisture away from the skin, combined with an outer fabric which spreads moisture across the surface so it can evaporate more easily.

Do they wear out? The answer is that most chemical treatments do eventually wear off. You can improve things by following washing instructions and using soap flakes rather than normal detergents, but with use, the wicking efficiency will definitely be reduced. Those fabrics which use the physical structure of the fabric are more resilient.

Softness Within reason, the softer the feel of the fabric the better. A rough surface can chafe nipples or other sensitive areas and simply won't feel as comfortable against the skin.

Cut If a baselayer isn't touching your skin, it can't wick moisture away, so what you're looking for is a snug but not overtight fit. Good baselayers have enough stretch to hug the skin, but without feeling restrictive. A snugger fit will also layer better under other technically-cut clothing. The one time you may regret this is when it's very hot and close-fitting garments simply feel too restrcitive and sweaty.

Form At it's simplest, a baselayer top can be just a tee-shirt, however the most versatile form is probably a long-sleeved zip-tee with a collar. Long sleeves and collar offer more insulation and comfort as well as protection from the sun, while a deep zip will help to vent your chest. keep you cool and flaunt your cleavage.

Colour No sniggering at the back, but if you're likely to be moving on glaciers, consider white or at least a very light colour to maximise heat reflection. It gets really hot when the sun shines and a dark-hued layer really does soak it up more. Sure, it'll be harder to keep clean, but what the heck.

Construction and Form Look for flat seams in areas which could come under pressure, or no seams at all. The classic point is over the shoulder area and under the arms where poor designed seams can rub under a rucksac strap or against your armpits. Under a fleece mid-layer you may not notice, but worn on its own, you probably will.

Odour Things have moved on since the days of 'Smelly Helly' - odour is generally due to trapped bacteria acting on debris and smelliness or lack of it varies a fair bit - washing regularly will help... The latest innovation is the incorporation of anti-bacterial silver threads in some fabrics, but as far as we're concerned, the jury's still out on that one, we've encountered a be-silvered example that smells like the worst of the worst before now.

The Nether Regions There's nowt worse than a pair of soggy cotton pants in winter so invest in a pair of baselayer grundies and stop the rot. Our twin faves right now are Lowe's men's baselayer trunks and Patagonia's silkweight Capilene boxers. Briefs, we've found, can dig into the wrong places. Ouch.