Do moisture-wicking fabrics work?

[Scott Emmens]

Hi Stephen, sorry for late reply. I managed to get one via the Canadian Distributor, I don’t think the Japanese versions would fit as well. I’ll get back to you with my experiences. Can you explain how the Finetrack philosophy fits in with your current tests? Thanks Scott

[Stephen Seeber]

Hi Scott:  Makes sense.  I was told by them that the Japanese sizes would not fit.

[Thomas]

I like to test my clothes when I’m landscaping, which is arduous work in these conditions:   Western Washington State, cold (30* to 45* F), humid, variable winds, sea level pressure, altitude < 500 feet.

I used to wear capilene or polyester “wicking” layer, then a light fleece layer, then a thicker fleece layer over that.  i would often get hot and sweaty and the wicking shirt remained wet and clammy, and I would take off both fleece layers for a while.  Then I began skipping the “wicking” layer, and just wore the 2 fleece layers.  That worked much better. Fleece does not absorb sweat from my skin, but nonetheless, eventually my body heat could itself evaporate the sweat.   Winds can go through the fleece layers, and so can my evaporating sweat.  My body’s skin has a temperature of around 94* F, and it makes sense to me to have the sweat as close as possible to the warmest heat source, i.e., in direct contact with one’s own skin, and not shunted away to clothing where it is of necessity cooler.

If the wicking layer is part hydrophilic, it seems it would harder for that part to actually let go of its moisture to the so-called hydrophobic part the exterior of the shirt, much less evaporate from it.  The hype is that it leaves the hydrophilic part of the very thin polyester shirt and moves outward to the hydrophobic part (of the same shirt, mind you).  What?  Doesn’t make sense really, if you think about it.  OK, the sweat spreads out, ok but does it evaporate easily?  My skin is still wet from sweat, because the interior part of the wicking shirt is hydrophilic.

For hiking in cold winter days (30s to low 40s F, humid, wet), I wear a light wool shirt over my skin, not for wicking, but for comfort and warmth.  Wool absorbs some skin humidity, then I take off a layer or 2, and it dries out.  I take off layers before I  sweat.

[Scott Nelson]

Could we see a link to this inexpensive Dozier base layer from Amazon?

Thanks,

Scott

[Stephen Seeber]

Here is the link:   Dozier

[Kirk Nichols]

Thank-you for this article on “wicking” and fabrics.

Now, irrelevant to fabrics, but misleading as a parallel process, is that plants, including celery, do not wick, nor is capillarity a dominant process in transpiration. Plants move water up through the xylem through a negative pressure system due to evaporation out the stomata in the leaves which then, though cohesion, creates a negative pressure in the vessels which draws water up the stem of the plant. This is neither wicking nor capillarity. Just don’t misuse plants as a parallel system even if the videos do. I spent graduate school as a plant eco-physiologist measuring fluctuations in negative pressures in thousands of plant stems. Sorry for the “geeking”.

[Ian H]

Kirk, that’s fascinating! Helps explain the really tall trees like redwoods and swamp gums where capillarity would struggle.

I’m currently reading emails in OR Echo at about 30 degrees C outdoor/35 degrees indoors in front of the computer screen. It’s one of the subjectively coolest fabrics walking in hot/steamy weather, but feels unpleasantly clammy sitting still. Icebreaker 150 or Capilene feel better at rest.

Then again, my legs below shorts feel almost as clammy! Time for a swim.

[obx hiker]

This is all great stuff. I’ve been trying to visualize the structure or outline of this whole series of articles and podcasts. Seems like this one might be described as materials and mechanics…. of the base layer. There are outer layers to consider as well.

Looking forward to the next podcast on managing perspiration in layering systems episode # 55, due out tomorrow.

I didn’t count; but it seems like a significant number of posts refer to what might be termed the management tactic of avoiding; as much as possible, sweating in the first place. (OK now that I’ve looked ahead at the podcast there’s a discussion @ 9 to 10 minute marks)

If you are sensibly sweating you are obviously too warm. Tricky business. Or is that even correct? Do we need a physiologist or similar?

I’ve seen some references to layering that seem to endorse slowing or controlling the pace of evaporation transpiration with less permeable layers. In the September 12th Q and A about clothing layering systems at about the 13th minute Ryan mentions sandwiching a wind shell above the base layer and below the outer insulation. This is described as a deliberate tactic to manage the pace of evaporative cooling by avoiding a “flash-off”. It does seem reasonable that, all things considered; managing the pace of evaporative cooling or next to skin warmth might be another complementary tactic when you get in a situation of unavoidably heavy sweat. Kind of time to go wetsuit and keep the next to skin layer and core ware while gradually releasing/evaporating that moisture. ( also what I would describe as controlling the pace of evaporation is also discussed. Heck maybe I’m getting schooled up finally. Sure am getting top notch instruction!

[obx hiker]

^^ Actually I just tried the link and  podcast 55 is active now.

[Aaron Reynolds]

In general I really like these science-focused articles, but the discussion of hydrophilic and hydrophobic surfaces here is way off. Water molecules are electrically neutral unless they gain or lose a proton through acid-base chemistry; they are not “slightly negatively charged” (and if they were, they would repel each other, which they don’t). This error led to the imaginative interpretation of hydrophobic surfaces as being strongly negatively charged (and hence, water-repelling). Teflon and paraffin wax surfaces are neutral, not negatively charged, and they sure are hydrophobic. The hydrophobicity or hydrophilicity of a surface is mostly determined by the extent to which water can form hydrogen bonds with said surface. There are no possible hydrogen bonding interactions between water and fluorocarbons, so Teflon makes an excellent choice for a waterproof membrane in a garment. Cellulose fibers on the other hand, with their abundant hydroxyl and ether groups, are reasonably hydrophilic, so cotton is out.

Also, clean glass isn’t hydrophobic. Why would you say that it’s hydrophobic? It’s incredibly hydrophilic, with water contact angles approaching zero degrees. The only exception is glass that has recently been heated to >600 degrees Celsius, and even then, a short exposure to ambient humidity will revert it back to its old hydrophilic self.

[Ryan Jordan]

Water molecules are electrically neutral

The electrons are not equally shared so a water molecule is polar with a slightly negative charge at O. They stick to each other because one side of the molecule has a negative charge and the other has a slightly positive charge. So when water molecules bond to each other, they do so in a fairly ordered fashion.

I’ll let Stephen address the glass issue to see what his intent was here. Pure silicon dioxide is hydrophilic, but many modern glass surfaces have semi-permanent hydrophobic treatments on them, and most glass cleaners leave a hydrophobic film on the glass surface.

[Aaron Reynolds]

Of course you’re correct that the electrons in each O-H bond of water are located closer to the oxygen atom, giving it a partial negative charge. That also gives the hydrogen atoms a partial positive charge of exactly equal magnitude. Add up the charge on each atom of an ensemble of water molecules, and I promise you that the answer is zero. Long-range order in water molecules, particularly in the vicinity of hydrophobic interfaces, is a fascinating and controversial topic. Solid-liquid interfaces are notoriously difficult to access experimentally, so a lot of it comes down to how much you like a particular water model that gets plugged into molecular dynamics simulations.

Over the last few years I’ve done my share of silane chemistry to modify the hydrophobicity of glass surfaces, which is why I felt strongly about the statement that clean glass is hydrophobic. Clean glass is beautifully, outrageously hydrophilic.

[Jerry Adams]

Lots of tech people here with good info

Plants bring up water by vacuum pressure

Then, it would only be able to bring water up 33 feet.  And if the vacuum was only half, it would be 16.5 feet

They must do something like bring the water up in steps

[Stephen Seeber]

Aaron:  I checked my reference for that statement and found the glass surface in question was indeed treated.  I  agree with your characterization of glass as hydrophilic.

Concerning the use of the electrical charge analogy: I have always found the discussions of high and low energy in reference to contact angle, hydrophobicity and hydrophilicity confusing.  I am neither a chemist nor a physicist and will happily be informed by those who are.  From an expository perspective, I found the electrical analogy to be more intuitive and useful, if not precisely correct.

[Aaron Reynolds]

Surface energy is definitely not an intuitive concept, and I very much appreciate the effort and time that you’ve put into writing this series. Your articles on moisture transport through windshirt fabric have been great, I would have never thought that a low cfm, high mvtr fabric could move moisture faster than a more permeable fabric.

[Author]

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