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TODO : Fabric Properties
Heat Transfer basics
General Fabric Characteristics
Wool Vs. Synthetics
Overstated Claims Of Wicking Fabrics
Clothing Color And Thermoregulation
Merino Wool Vs. Alpaca Shape Retention
- http://snarkynomad.com/why-merino-wool-t-shirts-are-the-best-travel-t-shirts/ (comments: ctrl-f: “alpaca”)
Alpaca does not have the extreme bending strength that Merino has, and so can loose its shape/form easier. However, this is easily remedied by putting a small amount of spandex, lycra or the like in with it. Plus, lighter/thinner garments like baselayers by nature, will have less problem with losing shape than their heavier sweater versions.
- Bending strength is much more important to me, especially with a baselayer. I would hate a garment that loosened up around the sleeves and neck after a couple of days, especially since I roll up my sleeves often. Just “adding lycra or spandex” to fix that issue isn’t great, because those fibers hold odor. 90% of the reason I use wool over synthetics is to avoid odor, not the properties of the fabric itself.
Fabric Needs To:
- Not be uncomfortable, itch, chafe (the softer the better)
- Dry reasonably quickly (the faster the better)
- Wick moisture away from skin to a reasonable degree (the more the better)
- Be reasonably breathable (the more the better)
- Insulate when wet
- Not smell even after repeated, sweaty use (have a microenvironment that prevents bacterial proliferation). *Dependent on use case. Most important if you won’t have access to a sink to sink-wash a synthetic shirt. Underwear and socks (if you wear them) should always be merino.
- Be light colored (for summer use: reflection of radiated heat from sun > reflected internal body heat: we are not pigeons. For winter use: when worn under other layers, light colors reflect more internal radiative heat than dark colors)
- Have enough absorption to still wick sweat even if the external surface is blocked (like sitting against something or wearing a pack)
- Be durable under normal use conditions (the more the better)
- Have good shape retention (therefore, not alpaca wool)
- Be water resistant (if possible)
- Be windproof/wind resistant (if possible)
- Be spark resistant (not fully fireproof but won’t melt on your skin either) – the more the better
- Be light: layering (fleece/down, shell) is superior to a heavy a single heavy shirt that you cannot take off
- Be natural, biodegradable, renewable (more important for something that is less durable – if you have a shirt that wears like iron, and you use it for 10-20 years, not such a big deal)
- Be static resistant
- Be stain resistant
- Be wrinkle resistant
- Resists pilling
- Has unique property of absorbing sweat while leaving the space next to your skin absolutely dry all the way up until the point it gets fully saturated at ~30% its own weight. Synthetic fibers like polyester will wick sweat, but will feel cold and clammy against your skin because the water is external to the fibers (these materials do not absorb any appreciable amount of water into the fibers). Cotton and other cellulosic fibers (Rayon, Modal, Tencel/Lyocell) will absorb liquid water between fibers (losing their insulative capacities by filling up air pockets), and thus will not be dry next your skin.
Evaporative cooling effect is spaced out over time compared to the synthetics (would you rather get chilled for a short period of time, or be cooled by gradual evaporation over a longer period?), and you won’t experience radiative heat loss in addition to evaporative cooling like you would with wet cellulosic fabrics.
- During strenuous activity in high heat high humidity situations, evaporative cooling will not keep up, so it is more a factor of which cooling type you would rather have once you come inside into air conditioning. During high heat low humidity situations, moisture control doesn’t really matter since evaporative cooling will actually work: loose fitting, breathable clothes are the answer in such circumstances.
- Evaporative cooling occurs on the external surface of synthetic fibers (where the water is), making them cooler than their surroundings. The evaporation of water from within wool particles still cools off the surrounding area, but the portion of the fiber in contact with your skin will not have the cold, clammy feeling.
- Anti-bacterial due to the microstructure of fibers (no external water, which bacteria need to survive – bacteria cause odor, not sweat itself). This is entirely natural, requires no chemical treatments, and will last the lifetime of the clothing (as opposed to a finite number of washes).
If evaporative cooling is a factor, it is theoretically more beneficial for evaporation to occur at the skin level rather than clothing level (i.e., the fabric should be vapor permeable, meaning that water vapor can transit the fabric). Sweating then having the liquid get wicked to the outside of the shirt and evaporate away from your body will not have an appreciable effect on body temperature (Wmich study). Since merino wool, Tencel, and most performance synthetics are all vapor permeable, this will not be a source of significant differences between the fabrics (as compared to, say, a synthetic shirt that was not vapor permeable, which would have the net effect of cooking you inside). Note that this discussion of is not related to “breathability” in the sense of air permeability: while this can increase air circulation and hence cooling by convection, it only really becomes relevant if there is some form of air movement to begin with (such as wind or airflow from rapid movement). (Wmich study)
Sorption: heat released from the exothermic reaction whereby water attaches itself to the inside of wool fibers – is still somewhat controversial within the scholarly literature, but it is generally agreed that it does not have any appreciable effect on body temperature (so cannot be viewed as a strong disadvantage during hotter parts of the year or strong advantage during the cooler parts of the year).
When fabric is in contact with things that block its exterior (such as a plastic chair back or a backpack), you still want some form of absorption so that you shirt does not stick to you. Synthetics will not have anywhere for the water to go so they will accumulate moisture and stick to you, while cellulosic fabrics will absorb the sweat interstitially and will likewise stick to you. In such a situation, wool is the only type of fiber that can deal with moisture without feeling wet and clingy on the skin.
Wool Vs. Tencel Vs. Poly/Nylon
- Tencel: softer than silk, more wicking than polyester (is this the same kind of wicking though?), more breathable than cotton, odor resistant. Says Lenzig literature.
Wool: only material that maintains insulation when wet, absorptive but dry skin feel, odor resistant, sorption (?)
- Ibex, Minus 33, Icebreaker, SmartWool, QOR
Synthetics: cheap, durable (abrasion resistance, if designed correctly), but smelly over time
- UPF – UV resistance and sun protection (change substantially when fabric wet?)
- Wool = better insulation from radiative heating of sun (direct sunlight won’t heat as much as a cellulose based fiber?)
- Coming in from sweating outside into air conditioning: no insulation due to wet Tencel in this circumstance leads to radiative heat loss
- Surface of tencel hydrophilic or hydrophobic, how this affects feeling against skin
- Hygroscopic — measure of water absorption (look at Lenzing lit.: does wool absorb more vapor than Tencel?)
- Can a shirt be 100% Tencel, or does it need that 5% spandex? How does this affect odor resistance longterm?
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