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Functional (as opposed to social) purpose of clothing is protection: from cold (including wind and rain which aggravate cold); from sun; from mosquitoes, ticks and other bugs; from thorns. My system is as follows: breathable shell garments directly against skin to protect from mild cold, wind, sun, bugs, and thorns; insulating garments over shell to protect from severe cold; waterproof shell over everything else to protect from wind and rain. Inner breathable shell has additional protective purposes: protects insulating garments from body oils; at night, protects sleep quilt from body oils; also at night, absorbs and wicks perspiration from parts of body pressing against non-breathable foam pad, and thus protects skin from developing pimples.
Qualities of nylon (also known as polyamide): strongest fabric for its weight, at least among fabrics commonly used for clothing; melts or even burns when exposed to fire (including sparks from campfire); deteriorates with exposure to ultraviolet radiation, such as sunlight; resistant to smells and cleans easily; absorbs more water than polyester and other synthetics. Compare with polyester: less strong than nylon for its weight, though not by much; melts and burns even more easily than nylon; much more resistant to ultraviolet radiation than nylon; strong tendency to pick up smells and hard to clean without using something like Mirazyme; absorbs very little water. Polypropylene is similar to polyester except absorbs even less water and melts and burns at a much lower temperature (commercial drying machines are sometimes hot enough to cause polypropylene to melt, so best to let it drip-dry).
Note that water absorption, smell resistance and ease of cleaning are related. A fabric that does not absorb water (hydrophobic) will tend to smell and be hard to clean, because water and soap won't be able to get into fabric to wash away body oils and other dirt that causes smells. Also note that water absorption into fabric itself is different from water being caught between threads which compose fabric due to capillary action—all fabrics are subject to second type of water absorption.
My own experience is that ease of cleaning and resistance to smell are most important factors in choosing clothing that will be worn directly against skin (at least when traveling and doing laundry in sink using cold water as opposed to using washing machine with hot water cycle), which is why I use supplex/taslan nylon (brandnames for types of nylon fabric which are most comfortable for wearing against skin) for most of my shell garments. Typically, I use 3 oz/sqyd supplex/taslan for my shirts and 4.5 oz/sqyd supplex/taslan for my pants. I replace these shell garments yearly or every two years, unless they have been damaged before that, such as from tearing on barbed wire.
For insulation, best choice is high-loft polyester with nylon inner and outer shell. Polyester fleece or stretch-knit is another good choice. Because polyester is hard to clean, best not to wear these insulating garments directly against skin, but rather wear them over breathable supplex shell garments. I make several exceptions to this rule. First, my hands produce little body oil, so I can wear polyester pile mittens directly against skin there. Second, I supplement wide-brim hat with insulating hood made of high-loft polyester sandwiched between nylon. This hood does tend to pick up smell due to body oils. However, I only wear this hood outdoors and in the cold, where smell is not much of a problem. Third, in cold wet weather, I used to wear polypropylene fishnet bottoms directly against my skin, but that was a special case and I no longer carry those bottoms. If laundering does not remove smell from either insulating hood or polypropylene bottoms, then Mirazyme should do the trick.
In the past, outdoor clothing was often made of wool as both shell and insulation. This is a heavyweight solution, especially when wet, but has outstanding advantage that wool (along with its close relation fur) is most resistant to smell of any fabric (though it has a smell of its own when wet) and easiest to wash free of body oil. Wool is also highly resistant to ultraviolet radiation and doesn't burn or melt easily like synthetics. In the past, I used wool/nylon blend for socks (now I use pure nylon), since feet produce most smell of any part of the body. I used fur felt in the past for my wide-brim hat (current wide-brim hat mostly made of nylon).
Cotton and hemp might be good choices for desert use, since they are fairly strong and very resistant to ultraviolet radiation. However, they are poor choices where moisture (either rain or perspiration that can't evaporate easily) is a problem, since they take forever to dry and are uncomfortable to wear when damp. Rayon and silk are too fragile for outdoor use, especially the latter.
Main problem with all waterproof garments is what to do about perspiration. A true waterproof garment will lock this moisture in. After much experience, I have come to the conclusion that rain gear should be used only to protect against torrential rain, and that otherwise it is better to just wear clothing that dries quickly and works well when damp.
Advantage of vests is they don't cause overheating so readily as jackets and pullovers, even when latter have pit-zips. But this is equivalent to saying vests don't insulate very well. So it will be necessary to supplement vest with something else, which tends to negate any weight advantage of vests. Jackets easier to get on and off, especially when wearing hat and poncho, but weigh more than pullovers. Be wary of zipper closures on both pullovers and jackets, since zippers can fail in the field. Zippers also difficult to operate with one hand injured. With or without zipper, pullovers can difficult to put on when injured. Best garment style is jacket with button closure and and wide draft flap.
Regardless of garment type, high-loft polyester insulation (polarguard, climashield, primaloft) is superior to polyester fleece and stretch-knit due to more loft for weight and better wind resistance, but equivalent moisture absorption and speed of drying. Advantages of fleece and stretch-knit are lower cost, which is non-issue in this modern age of cheap manufactured goods, and greater durability. Because lightweight polyester fleece or stretch-knit garments are so breathable, they can be worn in conditions where high-loft insulated garment would cause overheating. This is equivalent to saying these lightweight fleeces and stretch-knits don't insulate very well. As a general rule, for maximum warmth and minimum weight, use single thick high-loft garment. For maximum flexibility and comfort, at expense of somewhat more weight, use thin fleece or stretch-knit garment under medium-thickness high-loft garment. Be sure to buy all tops loose in underarms, whether shell, stretch-knit, or high-loft, to minimize contamination with underarm perspiration. Loose garments don't insulate so well as tight garments, due to bellows effect, but warmth less important than ease-of-care for long-distance hikers who will be living mostly in hotels.
Argument for tight-fitting base layer, of either wool or wicking polyester, runs like this. During exertion, body produces more heat than can be dissipated by radiation and convective cooling. Body responds to this excess of heat by perspiring. If we are wearing clothes, because air temperature is cold, then perspiration will be absorbed into clothing. Later, when we stop exerting ourselves, body no longer produces excess of heat, but on the contrary needs insulating clothing to conserve warmth. However, because of moisture absorbed by clothing during previous exertion phase, clothing has lost much of its insulating capability. Furthermore, as this absorbed moisture starts to evaporate, clothing will act like a refrigerator, due to evaporative cooling effects, which can bring on hypothermia. By wearing wicking but non-absorbent base layer, moisture will only be absorbed in insulation that is some distance removed from skin surface, which greatly reduces risks of evaporative chilling and hypothermia.
Close reading of the above argument will reveal a number of logical problems. Given that we were overheating during the exertion phase, why didn't we just remove some of our clothing then? That would have accomplished two things. First, without so much clothing, we would not have overheated so much, and thus would not have perspired so much. Second, without any clothing, absorption of moisture by non-existant clothing would have been impossible. Now granted, there are social and practical reasons why we can't remove all our clothing. But we can certainly remove most clothing. Removing excess clothing actually solves entire problem of what to do about perspiration due to exertion during cold weather.
By contrast, tight-fitting wicking base layer doesn't really solve problem but only mitigates major danger (namely, rapid evaporative cooling after exertion phase ends) while creating other problems. Body produces perspiration because it is overheating. If that perspiration is allowed to evaporate from the skin, as would happen if we were naked, we might be cooled down sufficiently to eliminate future perspiration. Wicking prevents such cooling, so body responds by producing ever more perspiration, thus pretty much guaranteeing that outer layers of insulation will become thoroughly sweat-soaked. Meanwhile, all this excess perspiration dehydrates body, depletes body of valuable salts, and fouls base layer. Wicking prevents us from noticing how much we are sweating, so even if we were prepared to remove some clothing to cool down, we won't know to do so. Finally, tight-fitting base layers are much more of a nuisance to remove and put back on than outer layers, such as an insulated jacket, so there is strong tendency to ignore need to remove clothing when wearing such base layers.
Instead of tight-fitting wicking base layers, what I recommend, for milder conditions at least, is a base layer of loose supplex nylon (ordinary loose-fitting shirt and pants, in other words), plus insulating and rain clothing as needed. By keeping clothing loose, perspiration will evaporate on the skin and thus cool the body, thus reducing further perspiration. When exertion is such that evaporation of perspiration is insufficient to cool body, then nylon will absorb moisture and begin to feel damp. This dampness is a signal to remove clothing. If this is impossible, then eventually nylon will become soaked with moisture. When we stop exerting ourselves, this moisture will evaporate. And yes, there will be tendency for flash evaporative cooling at this point. However, body's metabolic processes don't just suddenly come to a halt. Rather there is a cool down period during which body will continue to produce excess warmth, and nylon will tend to dry out during this time. Recall that nylon is very thin and hence absorbs only a limited amount of water and hence dries very quickly. In any case, even if nylon base layer isn't fully dry once body has cooled down and is need of insulation to conserve warmth, rest of the insulative clothing (such as a high-loft jacket) can be put on at that time. This clothing should be dry, because we had the sense to remove it as soon as we started perspiring. Hence this outer clothing should provide plenty of insulation to compensate for any evaporative cooling that occurs as remaining moisture in the nylon base layer is burned off.
Only type of tight-fitting base layer that really works is fishnet, because holes in fishnet allow perspiration to evaporate on the skin rather than being absorbed into base layer. Brynje of Norway fishnet is made of polypropylene. Polypropylene absorbs very little water but tends to stink when worn against skin. However, if a base layer is essential, such as during winter conditions or for hiking in cold rain, when pulling layers on and off is impossible, then polypro fishnet is the way to go. Another possibility is fishnet made of nylon, such as that of Wiggys. I examined Wiggys fishnet at home (though never wore it in the field), and found it to be heavyweight, uncomfortable and poorly-made, so I can't recommend it, especially not when the much superior Brynje fishnet is available. If fishnet is ruled out, then a combination of loose-fitting supplex nylon together with a high-loft pullover is normally better than using a base layer.
Many shirt-makers put polyester mesh in shoulder area of otherwise well-designed supplex nylon travel shirts. This part of the shirt then begins to stink even after cleaning, even though rest of shirt does not stink. Mesh is just a form of fishnet, which is indeed a brilliant idea in cold wet weather, as just noted. But ease of cleaning is more important in warm weather.
See the Health and Hygiene page.