The Wonders of Wool

November 8, 2008

Reading Time: 3002 minutes.

A few weeks ago I attended a very interesting seminar on extreme clothing in the Lakes, at which Mike Parsons, (founder of Karrimor and now Kimm), and Mary Rose (joint author with Mike of Invisible on Everest, a book on the history of outdoor gear I highly recommend), gave a very interesting talk on old school ‘performance’ fabrics. Sounds dull I know, but it wasn’t. They covered the usual stuff like state-of-the-art cotton coming out of Lancashire like Gabardine and Ventile, but also subjects like the first breathable waterproofs, amazingly used by the Aleutian Indians for thousands of years and constructed - wait for it - from seal intestines. They also talked about the Austrian Iceman (or was he Italian?) and how his jacket of grass was not only waterproof and breathable but was maintained by keeping the roots attached to the grass. It turned out that by the middle of the 20th century natural fibres had become incredibly high tech and effective at protecting us from the elements, with some possibly being far more effective than what we are now using today. By far the most common performance material on all early climbs and polar expeditions was, of course, wool which unlike other natural insulators like furs and feathers, was by far the most effective insulator outdoor people could hope to use, being robust, light and resistant to the environment (it stayed warm when wet).

For centuries people had been using this natural fibre to stay warm, with perhaps wool’s finest hour coming in 1953 when two blokes dressed in Shetland jumpers strode to the top of Everest. Like a modern team searching out for the latest synthetic fleece developments, Hunt’s expedition had jumpers made out of a specially spun superfine Shetland yarn, made using the highest grade of Shetland fleece, plucked from the neck area of sheep (the largest size weighed at just 185g). But, unfortunately, even with natural fabrics better than they had ever been they all disappeared to be replaced by synthetic versions, all of which promised to be lighter, tougher and, most importantly, cheaper.

Coming away from the seminar I thought what a shame that all that experience, gathered over perhaps centuries didn’t go to more use, after all, if wool is still good enough for your feet why isn’t it good enough for your body?

Coincidentally people had been asking me about wool base layers for ages, but I’d avoided using them, both because I don’t wear trad base layers much on trips (prefer less conventional laying) and because I’d had this new wool fad down as something that was worn by the type of outdoor person who also swears by silk underwear.


My past experience with wool had been varied. About 10 years ago someone had given me a Swanndri top, a much-beloved piece of clothing seemingly worn by all New Zealanders, (along with stripy Macpac long johns), telling me how it would change the way I looked at fleece. I seem to remember it was called something typically Kiwi like a Bush shirt (this was before Ray Mears made the word ‘Bush’ sexy), which was quite appropriate, as that was just what it felt like when you wore it. In fact, I found it so uncomfortable that I couldn’t stand to wear it for more than half an hour at a time, in fact, just writing this is making make me itch. My friend told me I should let it ‘break-in’ which didn’t sound convincing as the last person to say that had been the bloke who sold me his old Asolo Supersofts (they never did). The top was also cut in a ‘lumberjack’ style, which I’m sure is great if you’re chopping down trees, but when it comes to climbing, checked shirts with ‘70s style colours just don’t work, so I put it away in my cupboard for the day I put on 10 stone and bought myself a pick-up truck with antlers on the front (I’m halfway there).

I had a bit more luck with my second piece of woolly clothing, which I think was made by a company called Antarctica. This was thinner, with a more technical Zip-T design and, best of all, the wool fibres were much softer. Up to that point, I’d been using Rhovyl/modal and polypropylene base layers due to their high warmth when wet, but I was recommended to try out this top as it was, apparently, the dog’s doodahs. ‘Wool?’ I thought, why would anyone want to use a wool base layer when there are so many good man-made materials around? With the memory of my Swanndri torture still fresh I decided to give it a go anyway.

I wore the top for a trip up to Scotland and was immediately impressed by how comfortable and luxurious it felt, with its drape making it look far smarter when travelling to the mountains (not that I cared, of course) both things pointing to the top being a probable poor technical performer; after all function and fashion are rare bedfellows.

Once in the hills, I found that first of all it seemed that when I was working hard I only felt a dry heat, not the unusual damp-heat when the base layers wicking speed is overwhelmed, making overheating far less uncomfortable. The top also just seemed far more comfortable and natural than my synthetic base layers, oddly feeling as if it was part of me. The real test came a few days later when I set out on a run, hoping to link some Munros without any gear apart from the clothes I was wearing. Halfway around the heavens opened up and I got soaked, with a constant drizzle following me all the way around. To my amazement the top stayed warmer than any other wet base layer I’d used, keeping me totally comfortable as long as I was out of the wind. The fabric seemed to be maintaining a constant and comfortable temperature even when sodden, a little like my experiences with fibre pile, and was comfortable enough to wear once I got back to my car. A second important point was that it didn’t seem to stink like the other base layers I’d used (this was in the smelly Helly days) and although I wouldn’t claim it was odour free (it did have a wool smell), the smell was natural rather than positively supernatural (i.e. people fainted when the smell appeared). Once home the top ended up being one of the few bits of outdoor clothing I chose to wear every day as it was just so comfortable (plus I didn’t have to wash it for weeks). No doubt I’d have carried on wearing my beloved top to this day if my wife hadn’t stuck it in the tumble dryer and transformed it into something an action man could wear.


Thinking back to both my positive and negative wool experiences I decided to give this new wool thing a try, choosing a top from the New Zealand company Icebreaker as my test sample. Icebreaker is the company most responsible for breathing new life into performance wool and seems to have cornered the market at present. The item of clothing I picked was their Tech top as it seemed to be the most technical top on the market (hence the name). The main story here is the fabric itself so I’ll just give you a quick rundown on the top itself.


The first thing that makes this top stand out (and be technical) is that the sleeves come all the way down to the back of the hand and are secured by thumb holes (you can push or roll the sleeves up when not needed). This is a great feature and shows that the company is obviously making serious base layers as only the real outdoor user would see the benefits of what would appear to be weird - and, therefore, non-commercial - feature to any non-outdoor person (remember your wrist is the second greatest area of heat loss). I can guarantee once you’ve used a top with this feature you’ll never be able to go back. The top has a generous zip-necked design, with the double wool layered collar coming all the way up to your nose (or folded down to give you four layers around your neck). Although I’d like the zip to go down a few inches more it works well at opening up the top in order to let off steam and the sleeves are also cut so you can pull them off to cool your forearms (one of the most effective ways of cooling the body remember). The length of the top is long, so it won’t come untucked and overall the construction is solid and simple, but to see the real design genius you’ll need a microscope, but before we get to that let’s have a word for the top’s sponsor…


Sheep aren’t stupid if they were how would they come up with probably the most advanced natural robust insulation on the planet. Sure the duck and goose rule when it comes to pure weight for warmth insulation, but for wet hills and mountains, the sheep have got it sorted. We all know that man-made synthetic fills can’t touch down, yet when it comes to base layers we’ve all accepted that synthetics are as good as it gets, swallowing all those wicking diagrams and chemical processes needed to keep you dry. The thing is that when you compare millions of years of evolution with a century of fabric and chemical engineering all synthetics just haven’t hit all the bases yet, being cheaper, mass-producible, easier to manage and care for, for example, but not hitting the performance bases the user wants. The Merino sheep is the maker of nearly all the current crop of performance wool clothing, which isn’t surprising as it lives in New Zealand’s Southern Alps and, like the Siberian Husky, comes with a clothing system designed to keep it alive when all other animals would drop down dead (or freeze to the spot). Due to the harsh climate, the Merino has developed a fleece that can withstand both seriously cold winter temperatures and the extreme summer heat, with the superfine nature of its wool fibres being its secret. Each Merino produces enough wool to create about five pieces of clothing a year (there are 60,000 wool follicles per square inch of skin, producing over 100 million individual fibres in each fleece), meaning that when you take both that and the difficulties in managing sheep in such wild locations, you can see why Merino wool isn’t cheap and carries a premium price tag.


Like most articles I write I wanted to know more about wool than the surface facts (the ones that immediately float to the top when you think about things) i.e. ‘it’s warm when wet’, ‘it’s itchy’, ‘it doesn’t smell like Ian Parnell’s Himalayan undies’. I know all this is true but why?

First, let’s begin with a single Merino wool fibre. This is less than a thousandth of an inch thick (1/4 of the size of a normal wool fibre) and is made up, like all wool, of three main layers. First, there is a hydrophilic (water-loving) core made of a protein called keratin, which is present in all skin and hair and designed to maintain the homeostasis (a stable metabolic rate) of the body. The core is surrounded by overlapping cuticle scales (like shingles on a house), which are very tough, waterproof and also self-cleaning (when the fibre moves the scales brush against each other) and UV resistant, with most clothes having a high UV factor of UPF50+, important if you’re using the fibre to keep out the sun at high altitude. These scales are what can make normal wool itchy, but Merino wool being much finer (like silk) means that they’re too small to irritate the skin. This scaly layer is then covered by a filmy skin called an epicuticle, which acts as the fibre’s waterproof shell, causing water to run off and is the cause of water beading up on wool clothing as if it had been sprayed with DWR.

Sounds impressive doesn’t it, a waterproofed fibre. Well, it isn’t. Synthetic fibres are just as waterproof, as they are basically plastic and so can’t really absorb anything (hollow fibres can absorb 4% of their weight). The difference is that whereas synthetic fibres are 100% waterproof they are also non-breathable, with their wicking abilities coming from the way they are woven or knitted together to make the fabric (and what hydrophilic/hydrophobic chemicals they are treated with to boost their performance). The secret of wool is that amazingly the fibres themselves breathe, with the outer epicuticle layer and cuticle scales featuring tiny pores that allow moisture through but not water. This means that when you sweat the actual fibres soak up the moisture, not just the surface of the fibres. This moisture is absorbed into the protein core of the fibre, with the fibre being able to absorb 30/35% of its weight. This is not to say that your wool clothing will get to put on a couple of kilos then stop working, as the same processes are at work as with synthetic fabrics, namely the moisture wicks out towards the surface pushed by your body heat. Wool clothing will get heavier (as anyone who’s fallen in a river as a kid wearing a wool jumper will know), but because we’re only talking about very thin base layers then this isn’t a problem, as the base layer is the fastest drying item of clothing you have. What’s important is how warm the fabric is when wet - not how quickly it dries in a lab. The actual insulation properties of the Merino wool comes both from its super fine three dimensional ‘sprung’ structure (or crimp) which helps to maintain a very resilient dead air space, wet or dry (the fibre can be bent, flexed, and stretched in any direction 30,000 times or more without damage), which creates the perfect wet warmth environment to push the moisture in the fabric out across the temperature gradient on to the surface and eventually the atmosphere.

Probably the most amazing attribute of wool is that the wool isn’t dead like plastic and will actively try to maintain your comfort level, dynamically trying to achieve an equilibrium with the surrounding environment, absorbing and desorbing moisture vapour in order to maintain this equilibrium. It sounds hard to believe (and harder to understand), but this last fact explains a lot and may explain why wool base layers actually feel part of you.

There are loads more facts that I could give you (including a study that shows it reduces lactic acid build-up in the muscles), but I’ll save one of the best features till last…


Unlike synthetic fibres, most of which are produced at a considerable environmental cost; both in processing and in being part of the petrochemical industry, wool is a natural fibre and although is not without its own eco damaging processing, is far more ecologically sound. Unlike down, wool is harvested from a living animal and, as far as I know, there are no ‘battery’ sheep, with the Merino sheep living quite a wildlife in the high pastures of New Zealand. Wool is also biodegradable, just like the animals who made it, and one aspect I like about wool clothing is that it’s valued far more highly by the user, both because of the comfort and the price and not wanting to sound too new-age because it’s not a ‘dead’ fabric it feels like part of you. This means that the wearer may be more inclined to repair their clothing rather than just bin it and buy another top. Another big factor is that wool is a natural alternative to non-smell synthetic base layers which are impregnated with silver particles (a damaging environmental heavy metal) to stop smells from growing, as the fibre will not absorb liquids or oils. Although wool processing isn’t without its problems (chlorine is used for example), I’m reliably informed this new smell resistant process has an environmental impact (the water used in processing cannot be reused for example) and so a natural non-industrial alternative seems like a real bonus, especially in the fact that it actually works far better. I’m sure many people will find it strange that I rate the ecological angle as important and, no, I’m not aiming at becoming High’s answer to Sting, just that I think we need to start asking more questions about this kind of stuff.


Well as you may be able to guess from what I’ve written above, I’m convinced, and most others seem to be who’ve been turned on to wool (erm does that sound a bit rude?). I’ve worn the top more than any other testy bit of clothing this year, in fact, I’ve worn it since it arrived in the post a few weeks ago (I haven’t washed it yet), both for climbing, working and washing up. One thing I can attest to is its odour resistance, as it’s done over five hours worth of running, both in wet and hot weather, a trip to the Alps, a children’s party and it still doesn’t smell (in fact I’m wearing it now and I’ve just given it a quick sniff to check and it’s still okay). I do have a cold at the moment and my wife has been away in the Caribbean for a week (actually she went not long after I started wearing the top?), but I think this is an important aspect, as there is nothing worse when you’re on a big trip than stinking for weeks on end. Comfort-wise the top works amazingly well in the wet and dries faster than I’d expect and I think wool’s a bad rep at drying probably comes more from the denser construction used in old-style clothing. When the top was wet the first thing I noticed was it doesn’t seem to cling, which reduces conduction and has a much higher wet warmth than any synthetic fabric I’ve used. In fact, the comfort range of the top is huge, both due to the fabric and the design of the top and with the addition of a very lightweight windproof top, you have a system that works in almost all conditions when active. In reading this article I don’t want you to think I’m saying that Powerdry, Capilene and Dryflo etc are crap because they aren’t, all I’m saying is that wool has been greatly undervalued and that it isn’t a poor relation. In the coming year, I’m convinced you’ll see wool base layers appearing from many brands (some mixes of wool and synthetic I expect), so it seems a good time to put the case across.

As for drawbacks, it is dammed expensive, being twice as much as a man-made top, but then after reading all of the above don’t you think it should be? Oh yes, and it’s as addictive as crack cocaine, meaning you’ll go into cold turkey the minute it goes into the washing machine (or should that be cold sheep…?).

Why did climbers stop wearing wool?

Animal hair, whether camel, elephant, goat, horse or alpaca has been used by man for several hundred thousand years. But of all animals, the sheep, with its natural adaptability to a range of environments, was domesticated around 8,000 years ago and became a vital source of textile fibre. Certainly, sheep arrived in Britain before the Romans and wool was the most popular fabric for clothing precisely because of its versatility and insulation qualities. In mountainous areas, German and Austrian mountaineers used Loden (woven woollen cloth) weather capes to repel the weather long before mountaineering became a sport. Early mountaineers and explorers used wool too, for jackets and knickerbockers and the light Shetland pullover was a vital bit of kit. Dr. Jaeger’s ‘Sanitary’ Wool system was used by generations of polar explorers and mountaineers as a base layer. Camel’s hair is an even better insulator than sheep’s wool - the hollow fibre is the ideal protection against desert nights. Camel hair Jaeger sleeping bags kept mountaineers warm on many a bivouac by candlelight, right up to the 1920s. The heavily felted Dachstein knitted mitt has lost its popularity but is still available and much loved.

So why did so many people stop using wool from the 1980s if it was so good? Fleece was the answer. The idea of imitating animal fur with a pile fabric began during the Second World War but was not introduced for work wear by Helly Hansen until the 1960s. Those early pile jackets were functional but looked tatty very quickly. Fleece was different, it was both functional and looked good and, at a time when wool was relatively expensive, it took off. People wanted a change. The warmth: weight ratios are very similar for fleece and wool - providing you stay dry, if you don’t fleece is lighter and dries more quickly so you can carry less. Not everyone abandoned wool - many people still use a Shetland woolly is a mid-layer. Now that the price of wool has fallen it is beginning to make a comeback in sports wools - those blends of wool and polyester that bring the best out of both wool and polyester.

Mike Parsons, KIMMlite and Mary Rose, co-authors of ‘Invisible on Everest: Innovation and the Gear Makers’