Chapter 93 Outdoor Clothing for the Wilderness Professional
Lacking fur, feathers, or scales, humans must protect themselves from the environment. Clothing as an adaptive strategy has evolved a long way from unstructured hides. Protection from the environment and optimization of thermoregulation are the two primary purposes of clothing. Each individual produces metabolic or body heat. Well-designed outdoor clothing either retains or releases heat in response to the environment and individual comfort. Insulation from heat loss conserves energy that may then be applied to the activity being pursued. Behavioral adaptations further maximize this as the individual modifies clothing layers or the rate of exertion in response to metabolic needs and heat production. Clothing manufacturers take advantage of fiber qualities to design fabrics that enhance the performance of garments under all conditions.
There are several factors to keep in mind when choosing the appropriate clothing. These include the weather, influenced by geographic location and season; and the specifics of the activity, such as aerobic or high-exertion sports compared with sedentary tasks. One must also consider the length of the outing. For example, an activity in a remote locale lasting a long time will require different clothing than a short outing close to an urban environment. In the wilderness setting, the clothing one wears is not just for personal adornment or comfort—it may be a lifesaving feature (Box 93-1).
BOX 93-1 Considerations for Clothing Choice
This chapter discusses the various fabrics and fibers used in outdoor clothing and illustrates an adaptive strategy for picking the appropriate garment type and accessories for use in various environments (Figure 93-1).
FIGURE 93-1 Alaska hiking in Arc’teryx clothing and packs.
(Copyright 2008 Arc’teryx. Courtesy Brian Goldstone. www.arcteryx.com.)
Clothing, with the exception of leather and hide construction, is made from fabric woven from various fibers. The fiber type and diameter, density of weave, and presence of any treatments or finishes determine the fabric properties. The following four material properties pertain to fibers and fabrics:
Fibers may be natural or synthetic and may be woven from either or a blend of both. In general, natural fibers are softer and more durable than are synthetics. However, synthetics are lightweight and quick to dry.
Fiber density is measured in “denier.” Denier is the linear mass density of a fiber—measured as the mass in grams of 9000 m (29,528 feet) of a single filament of fiber. The word itself is an amalgam of the two terms—density and linear—and is pronounced “dun-ye.” A single strand of silk is measured as 1 denier and is the standard against which all fibers are compared. Denier is not a measurement of strength, but weight. In general, denser fibers are more durable and abrasion resistant. Ballistic nylon is at least 1050 denier and is most commonly used for bags and packs. In clothing construction, it is used to protect areas susceptible to abrasion, such as pant cuffs and shoulders. Although denier is a measure of weight and may correlate to durability, fiber diameter is another useful measure. Both intuitively and practically, finer fibers are softer to the touch and can be woven tighter. The diameter of natural fibers varies depending upon the source, making it too variable to assign a standard denier to each fiber type. The manufacturer determines diameter of synthetic fibers.
Cotton is commonly used for T-shirts and nontechnical clothing. It is very hydrophilic and has poor moisture regain. The fabric wicks moisture away from the skin—but does not redistribute it to the external surface for evaporation. It absorbs and holds moisture, rapidly losing any insulative value. Saturated cotton retains only 10% of its original insulative value. These properties make cotton very undesirable as an insulation layer in any cool environment where heat conservation is the goal. Conversely, in a warm or hot environment, cotton helps to keep a person cool. The moisture absorbed by the fabric contributes to cooling by both convective and conductive heat loss.
Wool and merino wool are excellent insulating fabrics (Figure 93-2, online). The core of the wool fiber absorbs moisture and redistributes it to the fabric surface, where evaporation occurs. This moderate affinity for absorbing moisture is countered by excellent regain—the fabric retains warmth and does not feel cool or wet when damp. Wool feels wet when saturated. Traditional wool can be highly irritating to the skin. Wool fibers have barbs in the epicuticle, or outer layer of the fiber. Merino wool is a finer fiber with fewer barbs in the epicuticle. Ultrafine merino wool fibers are 17.5 µm in diameter, allowing for lightweight fabrics and exceptionally tight weaves. (For comparison, a human hair is 60 µm in diameter.) Merino wool is machine washable with minimal shrinkage and is highly elastic. It retains its shape well with repeated wearing and washing. The antibacterial properties of wool contribute to decreased body odor retention—a very desirable quality when faced with multiple days of wear. The bacteria that metabolize sweat do not flourish; therefore less odor-producing metabolites are present.
Wool, including merino wool, is spun from the fleece of sheep. Alpaca and llamas are camelids, originally from South America (Figure 93-3). Cashmere is spun from the undercoats of cashmere goats. Although technically not wool, these wool-like fibers share similar properties with Merino wool.
Silk is used most commonly in base layers. Conventional, untreated silk retains moisture, although not to the degree of cotton. The majority of silk used for outdoor clothing is treated and wicks reasonably well. Silk is frequently blended with other fibers to smooth the texture of the fabric.
Down is the fluffy undercoating that keeps geese, ducks, and other waterfowl warm (Figure 93-4). It consists of clusters of filaments growing from a central quill point. Land fowl do not produce down. Goose down is superior to duck down in its loft and therefore ability to insulate. Down is an excellent insulator when dry. Unfortunately, the low moisture regain and hydrophilic nature of down make it almost useless when wet. The insulative value of down is measured in fill power. Each company uses a slightly different measurement, making across-the-board comparisons difficult. Generally, the higher the fill power, the greater the insulative value. Fill power is the volume that a specific weight of down occupies. In other words, the number of cubic inches displaced by a given ounce of down (in3/oz) is the fill power.
FIGURE 93-4 Down puff.
(Copyright 2010 Gary Peterson, Western Mountaineering. www.westernmountaineering.com.)
The highest-quality down has a fill power of 800 or greater and is usually goose down. Lower-quality products use duck down. A 600–fill power garment may be as warm as an 800–fill power garment, but more down is needed to achieve the same warmth, thus the garment will be heavier. Down is the preferred insulation in cold, dry environments when rain is highly unlikely.
Historically, protective clothing was made from animal products. Hides, feathers, and even intestines have been used to make garments. Northern indigenous peoples continue to use fur and pelts for outerwear. Pelts and hides are water resistant, warm, and physically protective. However, they are heavy and may be considered cumbersome. They demonstrate little flexibility or stretch. Fur trim may still be used around hoods and the sleeve cuffs but has largely been replaced with wool fleece or synthetic fibers. These trims trap air, which stagnates and warms, forming an insulating area around the face and wrists.
Leather is the finished product of tanned hides. It may be made from any animal, with cow, goat, and sheep being the most common. Leather, depending on the finishing process, can be exceptionally soft, supple, and thin, or it can be tough, thick, and abrasion resistant. Leather is commonly used in the manufacture of footwear and gloves, capitalizing on its durability. However, synthetics have replaced leather in most outdoor clothing. Abrasion-resistant nylon is now used on the cuffs, shoulders, and elbows, where leather may have been used in the past. Leather jackets and pants are still very common for motorcycle gear, and thick leather pants or chaps are still used by woodsmen. Leather is not water resistant and becomes readily saturated unless treated with agents such as mink oil, Sno-Seal, or other oil-based products.
Polyester is the general term for any petroleum-based fiber. It is widely used in the outdoor industry and highly versatile. Fibers are extruded or formed, not spun as are natural fibers. The fibers can be formed into nearly any thickness or configuration. Polyester fabrics insulate well because the fibers do not conduct heat efficiently. The fibers do not actually absorb any moisture. The moisture travels along the surface of the fiber and out to the surface of the fabric. Polyester fabric dries very quickly. These properties are used to their full advantage when polyester is made into fleece and sheets of insulation. Fleece is soft, washable, and durable. Bulky fleece traps air and is exceptionally warm for its weight. When fleece is tightly woven, wind and water resistance improve, but insulative value is diminished.
Polyester that is formed into sheets of insulation may be sewn into the layers of a garment. Polyester insulation has high moisture regain and good evaporative qualities; however, it is not as light or compressible as down. The fibers may deteriorate and break down with repeated use and washing and thereby lose the insulative value. Both down and synthetic insulations must be stored noncompressed. Prolonged compression damages both down and synthetic fibers, causing loss of loft and insulation.
Polypropylene was one of the first synthetic fabrics used for base layers. It wicks moisture well, has low thermal conductance, and is durable. Unfortunately, it demonstrates high odor retention and stains very easily. Other polyester fabrics, such as Capilene, Polartec, Coolmax, and REI MTS, have largely replaced it.
Nylon, like polyester, absorbs little water, which permits rapid evaporation. It has high moisture regain, is highly abrasion resistant, and melts easily. Nylon can be formed into large-diameter fibers and woven into highly durable fabrics, which are frequently used to reinforce wear points. Nylon must be tightly woven to protect against wind and water. This comes at the expense of breathability.
Manufacturers blend fiber types to use the benefits of each fabric. For example, spandex may be blended with the primary fiber, such as wool or cotton, to improve stretch and retention of shape. Wool may be blended with polyester to improve durability and fit (Tables 93-1 and 93-2).
|Insulative quality when wet||Poor||Good|
|Weight||Lighter per volume||Heavier than down|
|Durability||Will last longer if cared for properly||Will eventually break down even with ideal care|
|Care||Requires careful laundering||No special product required|
|Warmth||Greater warmth-to-weight ratio|
Waterproof/breathable fabrics are designed to repel precipitation and allow perspiration, in the form of water vapor, to escape. These actions help to regulate body heat by keeping clothing dry and preventing perspiration from accumulating within the clothing during exertion in rainy environments. Fabrics are made waterproof/breathable through the application of laminates, coatings, and durable water-repellent (DWR) finishes.
Laminate fabrics are designed by bonding a waterproof/breathable membrane to the underside of the garment’s exterior. They are commonly bound to nylon. If there are only two layers, the fabric is designated “two-ply.” The laminate may be sandwiched between two layers, thus creating a three-ply material, which is more durable but heavier than two ply. W. L. Gore and Associates produced the first waterproof/breathable membrane—Gore-Tex. This trade name is commonly, and incorrectly, used to refer to the entire category of laminate clothing (Figure 93-5). Although many manufacturers and laminate types now exist, the basis of laminate technology is the membrane. The membrane is formed of stretched or expanded polytetrafluoroethylene (ePTFE). The process of expanding the PTFE introduces microtears or holes in the laminate. These openings are small enough to allow water vapor of perspiration to escape (breathability), while not allowing water droplets to enter from the environment (water resistance). The pores of the ePTFE are 20,000 times smaller than the smallest raindrop, yet large enough to allow water vapor to pass to the outside. Water can only penetrate ePTFE if it is applied with a great deal of force or if the surface of the ePTFE is contaminated or soiled, leading to leakage. Two of the predominant manufacturers, Gore and eVent, use different methods to address soilage. Gore applies a microthin layer of polyurethane to the laminate. It is designed to be porous and not affect breathability of the fabric. eVent uses a proprietary method employing integration of a substance into the laminate itself. By preventing soilage, the waterproof and breathable properties of the fabric are sustained.
Coatings are liquid solutions, predominately polyurethane, that are applied to the interior of the garment. Microporous coatings are formed of microscopic channels that are too small for droplets to penetrate yet porous enough to allow vapor to escape. These channels form as the coating adheres to the surface of the fabric, either secondary to foaming agents that form interconnected pores or to introduced solids that cause microscopic cracks in the coating. Monolithic coating agents form a hydrophilic layer that transports moisture to the surface. Microporous and monolithic coating methods are virtually indistinguishable. Some manufacturers use both methods. Coated fabrics are not as breathable as laminates and are generally not as durable. However, they are more compressible and significantly less expensive than laminate fabrics.
Rubberized nylon is coated with a robust polyurethane lining that is not breathable but is waterproof. This fabric is ideal for marine environments and sedentary activities, when sweat accumulation is less of an issue for temperature control.
Soft-shell fabrics are the most newly developed fabrics in the outdoor clothing industry. This fabric type excels in breathability and flexibility yet still demonstrates moderate water resistance. Soft-shell fabrics have a tightly woven outer layer and an inner lining of varying insulative quality and may additionally employ a windproof or highly water-resistant laminate (Figure 93-6, online). They combine the properties of both an insulating middle layer with a protective outer layer. Soft-shell garments are highly effective for both temperature and moisture management in environments where rain is unlikely. They are moderately water resistant due to the tightly woven exterior surface and DWR finish. These garments excel when used during highly aerobic activities and in conditions where rain is not a concern. Soft-shell garments may function as both an insulating (middle) and outer (protective) layer.
A DWR finish is applied to all waterproof/breathable fabrics after the garment is completed. It does not change breathability of the fabric but enhances water resistance by causing water to bead up and roll off the garment’s exterior. The finish bonds to the fibers and does not fill the interstitial spaces of the fabric. An ideal DWR finish forms a dense chemical buffer on the outer surface of the garment. Microscopically, the finish forms an upright, spiky, and brush-like texture. Water thereby has a high contact angle with the finish, forming a spherical droplet. Were the contact angle to be low, water droplets would flatten into a more dome-like shape. This would allow the water to cling to the surface of the fabric and eventually seep in (Figure 93-7).
Dressing in layers enhances one’s ability to adapt to a changing environment. Each layer should maximize the properties of the fabric from which it is made. Layering allows for addition and subtraction of clothing as needed, adjusting for changes in body temperature and metabolic output, resulting in more efficient maximization of metabolic heat and enhancement of energy conservation. Adjustment of layers in response to changes in the environmental or travel conditions can prevent sweating and overheating, while preventing loss of heat that might lead to undesired cooling. In anticipation of increased body heat and sweating when traveling uphill, layers can be preemptively removed and zippers unzipped to enhance ventilation. Clothing that becomes saturated in sweat is not only uncomfortable, but loses its insulative properties as the fibers become soaked with moisture. This is clearly important in a cold environment, where loss of insulation or long drying times may lead to hypothermia. Removing layers in response to increased work also serves to conserve energy and moisture. In contrast to removing layers to prevent sweating, adding clothing layers as the workload decreases or the environment cools allows heat to be trapped in the insulative layers. The simple actions of managing a personal layering system conserve valuable energy for outdoor endeavors (Figure 93-8, online).
(Copyright 2009, Ryan Creary, Outdoor Research Marketing. www.outdoorresearch.com.)
An efficient layering system allows rapid response to changing environmental conditions. It is easier to replace a single garment that has become soiled or saturated than to replace an entire suit of clothing. Through layering, it becomes possible to not only pack fewer garments, but still be more comfortable across a wider range of environmental conditions and activity levels. When packing for any wilderness excursion, the unexpected needs to be considered, such as precipitation in the form of rain or snow, a sudden change in temperature, or the unexpected night out. When dressing in layers, fit is very important. The base layer should be snug but not confining. The middle layer should fit over the base layer comfortably. The outer layer needs to be large enough to fit over both base and middle layers without compressing. Compressing the middle layer reduces its insulative properties. Harness or pack straps should not rub or chafe on any seam or fold of fabric. Testing the fit, comfort, and effectiveness of the layering system before venturing into the wilderness will help prevent not only the discomfort of poor-fitting layers, but ensure that the purpose of the layering system is fulfilled—keeping one warm and conserving energy (Box 93-2).