A simple layering system consists of an inner layer of thin wicking material that removes moisture from the skin, a thicker midlayer to trap air and provide insulation, and a waterproof-breathable outer shell to keep out wind and rain while allowing perspiration to pass through. This neat three-layer system won’t cope with a wide range of conditions, however. Additional layers could include one or two more midlayers such as a wind shell or soft shell and a thick, insulated garment for camp and rest stops in cold weather. I often carry six layers—a thin base layer, two thin midlayers, wind shell, rain shell, and insulated top (see the trip sidebars in Chapter 2 for lists of clothing I’ve carried on actual trips). Several thin layers are more versatile than one thick one, which is either on or off, often leaving you either too hot or too cold. The boundaries of the different layers have always been a little fuzzy—thick inner layers can be used as midlayers, and windproof midlayers are also outer shells when it’s not raining—and this is getting fuzzier with garments claimed to function as all three layers. But nothing beats the versatility of having separate garments that you can combine differently according to the conditions.
WORST-CASE PLAN
Many years ago I came close to finding my own worst-case plan inadequate when I spent a week battling the high winds, lashing rain, and melting snow of an Icelandic June. I wore a wicking synthetic T-shirt; a thin wicking synthetic shirt; a thin synthetic-filled top; a thin synthetic windshirt; and a light waterproof-breathable rain jacket. I was barely warm enough when walking, because the rain jacket wasn’t breathable enough and I was permanently damp. Luckily I’d taken a vapor-barrier suit as backup, so I was able to stay warm in camp, but a thicker warm layer would have been a welcome addition.
Dressed for cold, stormy weather in New Hampshire’s White Mountains. Warm, waterproof hat, fleece-lined waterproof gloves, and waterproof-breathable shell jacket over windproof jacket and lightweight fleece top.
A base-layer top may be adequate on its own in warm weather. Add a thin fleece when the temperature drops. Wicking long underwear can be worn under trail pants in cold weather.
Clothing for wet, windy weather.
Hot-weather wear.
How much clothing you plan to take on a particular hike depends on the conditions you expect. I take enough to keep me comfortable in the worst likely weather. If I’m in doubt as to what is enough, I sometimes take a light insulated vest just in case.
I don’t carry clothing that can’t all be worn together if necessary. If it’s cold, I want to be able to wear everything. The only spare items I carry are underpants and socks.
The Inner Layer
Although it’s sometimes described as “thermal” underwear, the main purpose of the inner layer (also known as the next-to-skin or base layer) is to keep the skin dry rather than warm—often called moisture management. If perspiration is removed quickly from the skin’s surface, your outer layers keep you warm more easily. If the layer of clothing next to your skin becomes saturated and dries slowly, your other clothes, however good, have a hard time keeping you warm. No fabric, whatever the claims made for it, is warm when wet.
While you’re on the move, as long as your outer layer keeps out rain and wind and your midlayer provides enough warmth, you generate heat and stay warm even if your inner layer is damp. But once you stop, wet undergarments will chill you rapidly, especially if you’ve been exercising hard and producing a great deal of moisture. After a climb to a pass or a summit, you often want to stop, both for a rest and to enjoy the view you’ve worked so hard to reach. Once you stop, however, your heat output drops rapidly, just when you need that heat to dry out your damp base layer. But that damp base layer conducts heat away from the body, producing after-exercise chill. The wetter and slower drying your clothing, the longer such chill lasts and the colder and more uncomfortable you’ll be. Thus the inner and outer layers are important because they can minimize after-exercise chill by wicking moisture away from the skin and stopping rain from soaking your clothing; what goes on between these layers matters less, and this is where compromises can be made.
The one inner material to avoid is cotton, since it absorbs moisture quickly and in great quantities. It also takes a long time to dry, using up a massive amount of body heat. To make matters worse, damp cotton clings to the skin, preventing a layer of insulating air from forming. I haven’t worn cotton next to my skin for years—not even on trips in sunny weather when some people like light cotton or cotton-blend garments because they’re cooling when damp. I find thin synthetics or wool more comfortable than cotton in the heat, and I don’t need to change my top if the weather turns damp or cold.
Base-layer fabrics remove body moisture by transporting or wicking it away from the skin. Synthetic fibers are hydrophobic—they repel moisture—and tend to wick quickly. Natural fibers like wool and silk are hydrophilic—water loving—and absorb moisture into their fibers before passing it more slowly to the outside.
Synthetics can wick moisture by being nonabsorbent and having an open weave through which the moisture quickly passes, and having hydrophilic (water-attracting) outer surfaces that “pull” moisture through the fabric and away from the skin. In both cases, body heat pushes the moisture through the fabric.
Although synthetic wicking fabrics are very good, they can become overloaded with sweat and end up very damp on the inside. An important factor is the time they take to dry when you’re not producing enough body heat to push the moisture through the fabric. The best are those with brushed or raised fluffy inner surfaces that have a minimum of material in contact with the skin, letting it dry quickly. If the inner surface is smooth and tightly woven, moisture passes through it more slowly. Oddly, both tightly woven and open-weave outer surfaces can speed moisture movement. In the first case moisture can spread out over the surface of the fabric and evaporate or pass into the next layer; in the second case the open weave allows moisture to pass through very quickly. Fabrics with different materials on the inside and outside are known as bicomponent fabrics. Examples include Polartec Power Stretch, Polartec Power Dry, and Páramo Parameta S.
Most fabrics come in several weights. The lightest—sometimes called silkweight—are very thin and fast wicking, ideal for aerobic pursuits such as trail running but also good for backpacking, either on their own in the heat or under other layers in cold weather. Midweight underwear is slightly heavier and thicker and usually has a tighter weave. It’s warmer but often wicks more slowly, which is fine in cool weather. The heaviest and thickest fabrics are labeled expedition or winter weight. Most of these don’t wick moisture or dry as fast as the lighter fabrics and are better suited for midlayers. A few, like Power Stretch and Parameta S, wick as well as or better than thin fabrics.
Designs are usually simple; most tops come with either a crewneck or a turtleneck with a zipper, buttons, or snaps at the neck. You can get short or long sleeves; I prefer short-sleeved crewneck T-shirts for warm weather and long-sleeved zippered turtlenecks for colder weather. The latter are good as midlayers too. Close-fitting garments are much more efficient than baggy ones. My partner, hiker Denise Thorn, says she didn’t realize how effective base layers could be until she wore women’s styles that fitted properly rather than loose “unisex” tops. Most makers now offer women’s and men’s base layers, while some companies like Wild Roses (now called OR Women) and Isis make only women’s clothing. There are also bras made from wicking fabrics.
Figure-hugging “tights” are the norm for long underpants. Underpants made from wicking synthetics are far superior to cotton. Close-fitting garments help trap air and wick moisture quickly and also fit easily under other garments. Long pants should have a particularly snug fit to avoid the discomfort of baggy long johns sagging down inside other layers; elasticized waists are essential. Long backs stop tops from riding up at the waist. Stretchy fabrics often wick fastest because of their close fit. They’re generally more comfortable, too. Seams should be flat sewn to avoid rubbin
g and abrasion. Dark colors show dirt and stains less, but white or pale colors reflect heat better when worn alone in warm weather.
Choosing a wicking synthetic fabric can seem hard because there are so many, each with a fancy name and claiming to work better than the others. Actually there are only a few base fabrics, and they’re all derived from petrochemicals. Polypropylene was the original fiber used, but most base layers are now made from polyester. Other fibers like chlorofiber, acrylic, and nylon have just about disappeared.
The Smell Factor
Synthetic base layers are notorious for smelling bad, sometimes after only brief use. Ironically, the hydrophobic properties that make them effective at wicking moisture are the main reason for this. Your body moisture contains oils that stick to the fabric as the liquid evaporates or moves into your next clothing layer. These oils attract bacteria and can also undergo oxidation, both leading to nasty smells. Like the fabric, the oils are hydrophobic. Washing in cool water doesn’t remove them. Hot water does, but not all fabrics can be washed in hot water without shrinking, making it hard to get the smell out. Hanging clothes in the sun and wind can help, as can repeated washing in plenty of detergent and soaking in cold water with a little dissolved soap. It’s best, though, to choose garments that can be washed and dried at hot temperatures. This is also useful for long hikes when you want to chuck all your dirty clothes into a washer and dryer at town stops without worrying about the temperature.
Many fabrics have antimicrobial treatments. Most work a little but don’t stop garments from smelling for very long. Fibers such as X-Static that contain silver—a natural antimicrobial that contains no chemicals and is safe next to the skin—work best. Odor Resistant Polartec Power Dry contains silver fibers. Silver can’t wear out or be washed out, so it lasts the life of the garment. It’s said to remove 99 percent of bacteria in an hour and to work best in warm, humid environments. To test this, I wore an X-Static top for chopping firewood, day hikes, and cycle rides as well as backpacking trips. After two weeks’ wear, my unwashed top smelled faintly musty, but nothing worse. My family didn’t tell me to change it and take a shower. Synthetics incorporating silver fibers seem to be the answer to stinky synthetic underwear.
Fabrics
POLYPROPYLENE “Polypro” is the lightest and thinnest wicking synthetic. Introduced by Helly Hansen in its Lifa line back in the 1970s, it dominated the market for a while but is now found mostly in budget garments. Polypro won’t absorb moisture but quickly passes it along its fibers and into the air or the next layer. It wicks away sweat and dries so fast that after-exercise chill is negligible. However, it’s the worst synthetic fabric for stinking, producing a stench that can be hard to get rid of. Apart from the odor, if you don’t wash it at least every couple of days, polypro ceases to wick properly, leaving your skin clammy and cold. On long trips you have to carry several garments or rinse one out regularly and learn to live with the smell of stale sweat.
Polypro’s drawbacks are mostly overcome in Helly Hansen’s Lifa range. Helly’s polypro has a softer, less “plastic” feel than standard polypro, and it can be washed at 140°F (60°C), a heat that rids it of the noxious aroma. It’s also said to be resistant to the bacteria that cause smells. Lifa polypro comes in three types: thin, stretchy Lifa Sport; midweight Lifa Active; and Prowool, which has an outer layer of merino wool. I’ve worn a Lifa Sport crewneck top for several days without washing it, and though it smells faintly musty, I can bear to have it in the tent, something I wouldn’t do with the old polypro after even one day’s wear. It wicks moisture efficiently and, I suspect, faster than standard polypro. My crewneck Lifa Sport top weighs 5 ounces; my bottoms, which I mostly carry for campwear or unexpected cold weather, weigh 3.75 ounces.
POLYESTER Polyester repels water but has a low wicking ability—not ideal for underwear, since sweat just stays on the skin. However, it can be treated with chemicals or mechanically altered so that it becomes hydrophilic, resulting in moisture being drawn through the material to the outer surface, where it spreads out and quickly dries. The drawback is that after repeated washings chemical treatments wear off, though this isn’t the problem it once was. When this happens the material stops wicking.
There are many wicking polyester fabrics. Some are proprietary like Patagonia’s Capilene, GoLite’s C-Thru, REI’s MTS, and Lowe Alpine’s DryFlow. Others, like Polartec Power Dry, CoolMax, Thermolite Base, and Akwatek, are used by many companies, though they may appear under names like Marmot’s DriClime, which is Power Dry. Over the years I’ve tried many polyester base layers and concluded that they all work pretty well and there’s not much difference between them.
Of the expedition-weight polyester fabrics I’ve used, two stand out. Polartec Power Stretch and Páramo Parameta S both wick moisture faster than any other materials of similar weight and better than many lighter-weight fabrics. Both materials have soft, brushed inner surfaces that wick moisture rapidly and smooth, tightly woven outers that spread the moisture so it evaporates quickly. Power Stretch is used by many companies; my zip-neck top and tights are made by Lowe Alpine and weigh 10 and 7 ounces, respectively—less than some expedition-weight fabrics that aren’t as warm or as efficient at removing moisture. As the name suggests, the fabric is very stretchy and hugs the body. Parameta S doesn’t stretch and is exclusive to Páramo. I have the Trail Shirt, a conventional design with a collar, two chest pockets, and a snap-fastened front. It weighs 14 ounces. All Parameta S and some Power Stretch garments (such as Mountain Hardwear’s Zip T) can be reversed so the smooth side is on the inside. This is meant to make them cooler and thus increase the temperature range over which the garment is comfortable. It works to some extent, but I still find the Trail Shirt a bit warm in hot weather. I’ve had my Power Stretch and Parameta S garments for many years, and they’ve proved very durable. I now mostly wear them as midlayers.
Weights for base-layer tops and bottoms range from 3 ounces in light garments to 14 ounces for expedition-weight ones. Briefs start at about 2 ounces.
WOOL Wool, the traditional material for outdoor underwear, has had a remarkable revival and is now regarded by many as the best choice for base layers. I tend to agree. Though it might seem that wool wouldn’t fit into a layering system with high-tech synthetics, it does. Wool is excellent at drawing moisture into its fibers and leaving a dry surface against the skin. It can absorb up to 30 percent of its weight before it feels wet and cold, so after-exercise chill is not usually a problem. I’ve worn wool next to my skin on many winter ski tours and have always felt warm, even in camp after an energetic day. On those tours I’ve also worn the same top for two weeks with no odor problem. Because wool is hydrophilic and absorbent, body oils go into the fibers rather than staying on the surface and attracting the bacteria that cause smells. Wool’s limitations used to be its warmth, which made it useful only for cold weather, and the need for careful washing, often by hand. Now, however, there are very fine tops that work well in the heat and that can be machine-washed without shrinking. Wool does stretch slightly, though it usually regains its shape when washed. It is pretty durable, too.
What puts many people off wool is its reputation for being itchy. Old-style wool with coarse fibers could irritate the skin, though fine knits have always been available. When I began backpacking I wore a thin lambswool sweater I bought from a department store as my base layer in cold weather. I don’t remember it’s being itchy. The best wool base layers are made from fine, soft merino wool, which feels luxurious next to the skin, far more comfortable than any synthetic I’ve ever worn. SmartWool began the return to wool with its merino garments. Many others have followed as people learn just how wonderful wool is to wear, but of the garments I’ve tried, SmartWool still has the edge on softness and comfort. As a final plus, wool is a good material to wear around fires, since it doesn’t burn easily or melt like synthetics, making it much safer and less liable to be damaged by sparks.
Wool is also relatively light; I
have an Icebreaker long-sleeved crewneck merino wool top that weighs 7 ounces and a SmartWool Aero short-sleeved merino wool T-shirt that weighs 6 ounces, only a little more than equivalent synthetic ones. Both are light and cool enough for warm weather. Thicker, warmer garments weigh more, of course. My SmartWool Traditional Long Sleeve Crew and Traditional Relaxed Tights weigh 12 ounces and 9 ounces, respectively. These are warm garments, however. I wear them only when I expect temperatures to be below freezing. The top makes a good midlayer. Terramar has some good merino wool base layers, too. Its long-sleeved crew weighs 10.5 ounces. Terramar also makes polyester-wool mix and polyester-wool-Outlast acrylic garments (for my opinion on Outlast, see page 75). Wool-synthetic garments work quite well in my experience, though they’re not quite as comfortable as pure wool. Ibex also has a good reputation for its wool base layers (and other wool clothing), though I haven’t tried any of it, and Arc’teryx has a new line of merino wool base layers.
SILK Silk is the other natural material used in outdoor underwear. Like wool, it can absorb up to 30 percent of its own weight before it feels damp. Silk’s best attribute, however, is its luxurious texture; it’s light, too—a long-sleeved top weighs 3 to 4 ounces. A silk top I wore on a two-week hike in damp, cool weather kept me warm and dry, and at the end the odor was negligible. It was badly stained with sweat and dirt, though. When I rested after strenuous exercise, the top felt clammy for a few minutes, but then it warmed up. I probably won’t take silk on a long hike again, though, because it demands special care; it has to be hand washed and dried flat, and it won’t dry overnight in camp unless the air is very warm. Among those offering silk garments are Terramar, SilkSkins, and REI.
Chris Townsend Page 20