Wicking baselayers, a thought experiment

[Tjaard Breeuwer]

The last few years, I have been thinking about wicking baselayers, spurred by Stephen Seeber’s testing.

Besides the fact that very few (any) tested fabrics actually were capable of high volume wicking (very few achieved high wetting, and high wicking), there is a bigger issue:

• The claimed purpose of a wicking base layer is to prevent moisture build up in your clothing system
• Wicking can only occur occur as long as the moisture at the outside surface of the wick evaporates

What drives that evaporation? Our body heat. So, if we wear a theoretical, perfect wicking baselayer, we can evaporate all the moisture possible at a certain vapor pressure differential.  After it’s done that, the water vapor must still move through our insulation and shell layers.

What is the benefit the wicking  baselayer provides in that situation? It does not provide any additional moisture moving “power”. The rate of moisture movement is still ultimately limited by the ratio of body heat/environmental conditions.

Basically we have a bucket brigade moving water from skin to outside. Inserting a section of conveyor belt into our bucket brigade can never improve the performance of the total brigade.

[Jerry Adams]

yeah!

maybe a wicking layer will make you feel better, less clammy or something

but maybe you want to feel clammy so you’ll know you have too much insulation, you’re sweating, need to remove some of that insulation

the goal shouldn’t be to evaporate the sweat, but to not create it in the first place

maybe some activities will cause sweating regardless.  Cross country skiing for example.  Even if you remove insulation.  Maybe in that case a wicking baselayer would be useful

[jscott]

I found that a merino base would wet out pretty bad when I Nordic skied. Stopped using it very quickly. The upside of Nordic skiing is that you’re often creating an evaporative wind that helps wick sweat. Or simply skiing downhill…

[Paul McLaughlin]

I’ve come to the conclusion that it’s mostly about how fast my base layer dries. To some degree I can manage how much I sweat by peeling off outer layers in a timely manner, and i fo, but sometimes one’s timing is off and sometimes I’m sweating in just the base layer. And then it comes down to how fast it dries which is mostly (I think) based on how little the fabric absorbs.

[Atif Khan]

Tjaard,

Evaporative cooling at the skin decreases.

[Albin Zuccato]

Following your idea of a thought experiment I would suggest it is a question of “timing” why we want wicking and not a question of throughput.

Sweating and the resulting cooling is desired to prevent the body from overheating. This is especially important when exerting as the body needs to get rid of the excess heat or die. Evolution has “optimized” us to stop sweating when we are cool enough as it would consume resources (sweat) and would render us less effective. Why it becomes a question of timing is that we would like to stop the cooling when we stop working (or shortly after).

The challenge is the time delay introduced by clothing. The transport from the skin, where cooling optimally should happen if one would wear the birth suite, to the outside of our clothes, where cooling necessarily must happen, is delayed by the cloth’s different properties. The less resistance the clothes pose for this sweat transport the lower the time delay. The worst-case scenario is when the sweat “stays” in the wet(-out) clothes, or is put into the cloth fabric like wool, the delay is even further increased. This to the point where the body is no longer producing heat and cooling becomes a problem. (Note, that if the rate of evaporation is slow enough that it does not sip “too much” heat we can sustain it – like wool has a slow enough drying process and is therefore not uncomfortable – it still takes the energy though.)

To conclude the more wicking, the thinner material or the less layers we have, the faster the transport occurs and the less cooling at inappropriate time we get. This is because the body stops sweating.

Going with your conveyor belt example sure enough does not help with the throughput of your bucket brigade, but it increases its speed. Hence the delay until the sweat is out, evaporates and the cooling stops.

[Jerry Adams]

why is wool and even worse cotton so bad?

maybe it’s just how much water the clothing can absorb.  If it absorbs more then it’ll take longer to dry out from body heat and evaporation

a synthetic that absorbs less water will feel warmer because it doesn’t absorb so much water so takes less time to dry

 

[Terran Terran]

Absorbs vs adsorbs. Synthetics don’t absorb water. They adsorb it on the outside of the fiber.

[Jerry Adams]

so, that’s maybe why they’re better when wet – no water absorbed in fibers so there’s less to evaporate

[Terran Terran]

Natural fibers have more air spaces to absorb and hold moisture. Better insulation than synthetics.

[jscott]

“Natural fibers have more air spaces to absorb and hold moisture. Better insulation than synthetics.”

so, natural fibers (wool) better at retaining heat when sweating is not an issue; synthetics, better at not absorbing moisture and so wick faster than natural fibers….is this about right?

Cotton kills. that I can remember. Along with, “speeding kills bears”. (this last appears on road signs throughout Yosemite. I still think about it when I hit 75 mph on the freeway.)

[Tjaard Breeuwer]

“Atif KhanBPL MEMBER

Tjaard,

Evaporative cooling at the skin decreases.”

Why?
The same amount of water must still evaporate, but now it is doing it on the surface of a baselayer. The energy for that phase change still has to come from your body right?

And the other point is, the whole reason you are sweating is to cool down.
If it was somehow possible to lose less heat evaporating sweat from the outside of your wicking baselayer than from your skin,  that would  be counterproductive, leading you to sweat more and have even more moisture to deal with.

[Atif Khan]

Stylized, total system energy is the same but the rate of evaporation is higher where molecular density is greater, near the skin.

[Terran Terran]

It really should be  just a small amount of water vapor. If it’s more than that, you’re overdressed. I adjust my base layer for the heat of the day or by how much work I expect to be doing. Moisture travels away from your body with the hot air. It travels through the base layer. The base layer isn’t wicking water away from the body. At least that’s not it purpose. Now if it’s hot and I’m naturally sweating, cotton will wick the water keeping me dryer. Cold isn’t an issue.

[Tjaard Breeuwer]

“Atif Khan
Stylized, total system energy is the same but the rate of evaporation is higher where molecular density is greater, near the skin.”

Ok, I see what you mean. That makes more sense. So if I understand you correctly, you are saying that a certain amount of moisture will evaporate faster off the skin than off the outside of a (wicking) base layer?

What would be the benefit of the baselayer then?

Wouldn’t that still have the same effect of disrupting the body’s temperature regulation cycle?

Because now, when you overheat, you start sweating, and it takes longer for that sweat to evaporate, so the rate of cooling is less, so your body remains overheated for longer, and produces more sweat overal?

Versus wearing no baselayer:

body overheats, sweat produced, evaporates and cools rapidly, and so body temperature regulates faster, and less moisture is lost.

 

[Terran Terran]

Insulation in cold weather. To wick up sweat in hot.

[Jerry Adams]

yeah

another thing is to absorb body oils in winter so it doesn’t contaminate the insulation

if the base layer is just for insulation, then a layer of fabric is the least warmth for the weight.  Fleece is better.  Synthetic insulation like apex is better than fleece.  Down is better than synthetic but it doesn’t like getting wet

[Atif Khan]

Tjaard, What Terran said + with merino wool, whatever the word is for smoothing temperature variation at the skin (modulating? tempering?).

[Terran Terran]

“Modulating” would work. “Equilibrium”perhaps?

Wearing insulation isn’t natural. When we try to change nature (there’s many proverbs), we incur other  challenges, in this case vapor management. In doing so, we use natural materials or try to imitate them. That in turn leads to other challenges. We get to the point of “very good”, but never perfect. Nature is perfection in itself in an imperfect world. 

[jscott]

“Wearing insulation isn’t natural. When we try to change nature (there’s many proverbs), we incur other  challenges, in this case vapor management.”

Well…recently there was an entire movement towards running barefoot, or as close as possible, because shoes ‘weren’t natural”. Evolution meant us to eat meat and not fruit and grains, it’s said by some; we should be living on deer and raccoon!  For that matter, we were meant to get sick and die by the time we’re 35, in the “natural order” of things. Penicillin isn’t natural; neither is flossing; neither are aspirin or mattresses. we should reject all of that, as the Christian Scientists say. Wool is anti-natural, in that it requires technological innovation on the part of humans to produce. Synthetics are the devil’s playthings! Better to go naked.

 

[Terran Terran]

I’m not rejecting shoes or technology. A little early rambling saying with different insulation, there’s different challenges. It’s hard to beat natural fibers.

[S Long]

There’s a reason Scandinavians tend to like Brynje. Maximum air-pocket creation, and minimal fabric to absorb or hold sweat. The Vikings had it right all along!

[jscott]

“I’m not rejecting shoes or technology. A little early rambling saying with different insulation, there’s different challenges. It’s hard to beat natural fibers.”

Absolutely, Terran! I was trying to funny/silly. Of course you’re not rejecting shoes etc. I like Mr. Natural and follow a natural philosophy as best I can. And I dislike the feel of synthetic materials against my skin.

[Terran Terran]

Jscott,

I took your post as intended. I was backtracking, trying not to get too “political”. I think sometimes we expect everything to just work when there’s always a challenge.

A base layer will allow moisture to move away from our body. If you’re wearing a hard shell, it will condense on the shell. If you’re overdressed, you’ll get wet. It’s not going to evaporate. You’ll need to vent. It’s an imperfect system, yet a good one.

[Brian W]

What works best for you when you’re hiking or backpacking?  I’ve landed on a thin wool base layer. I’m always open to try new things, but after experimenting, it’s what I feel most comfortable in after and during a trek in the summer and shoulder seasons.

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