Do moisture-wicking fabrics work?

[Roger Caffin]

Hi Stephen

Do not equate the size of the pack with its weight! Big mistake!

My pack weighed about 12 – 13 kg, with food for a full week in it, plus everything one might need for extreme bad weather and sub-zero conditions. We got the extremes all right.

Thing is you see, when the pack is large you don’t need to really compress everything. So I didn’t. But I did have a winter down bag, and over-quilt, puffy, etc. Just not compressed real hard.

I suspect that Polartec may sometimes buy in a fabric rather than make it themselves. They all do that. Under magnification they do both look very similar.

Anyhow, thanks for the article.
Cheers

[Ian H]

I always love your articles Stephen. Especially being independent of the manufacturers who are trying to sell us a story. I have a few scientist friends who’ve wintered in Antarctica, and one of the first things they were taught was not to overexert, because the windproof outer layers hold the sweat in, so it freezes once you slow down.

Here in Sydney we’ve just had a week of 30° temperatures (85°F) with intermittent heavy rain and about 90% humidity. The super lightweight synthetic fabrics from OR and Salomon seem to be the best T-shirt material that let air through to the skin, so there is some direct evaporation from the skin. They do get sweat wicking also. The heavy rain was too annoying for dogwalking in a T-shirt, so after some in vivo experimenting, the thin T-shirt plus a Patagonia Houdini was the least unpleasant option for an hour or so. A Labrador fur coat and intermittent shaking also seemed to work, for my colleague who doesn’t sweat.

I doubt there is a test for it, but real world wicking seems a bit different than the sponge block technique, because there is pressure from movement and pack straps etc. Some sort of sliding/pistoning mechanism might show whether the fabric allows more moisture transfer under conditions of movement, where droplets get physically pushed into the fabric. The shirt is always wetter under the pack straps. I also wonder about chemicals like sunscreen, underarm deodorant etc, which must greatly affect the hydrophobic/philic balance even on a day walk, and maybe have a cumulative effect.

The other ‘comfort’ trap is like alcohol for hypothermia, what actually feels good for you may be bad for you, giving a false sense of security/skin comfort. Again, not sure how you’d test for it, but evaporation from skin is probably mostly human powered at low temperatures, definitely more wind powered at 30-40+°C. Does evaporation from clothing occur due to inner heat (cooling the body) or evaporation/sublimation down a concentration gradient of a cold dry wind (less cooling of the body)? The ultimate advantage of a cold weather wicking layer would be if the sweat evaporation from the outer fabric was powered by the wind, saving core body warmth, not just feeling drier.

The similar technology is in the disposable nappies/diapers my grandkids wear, which hold the liquid in a hydrophilic layer, but feel more dry in the hydrophobic lining than the old cotton ones my kids started in. Not a problem if you can remove the wet layer, like Ryan’s exertional sweat, but risky if you can’t remove the moisture which then freezes.

[Chris]

Nice write-up! Admittedly I need to read it some more to digest the details.

In addition of the stated topic (wicking claims vs. wicking performance), which is important, the article also got me thinking about the role of wicking in actual use – particularly high-exertion activity in cold weather. Is wicking an effective method of moisture management, and if so under what conditions?

I’m pretty hot and sweaty and have tried a lot of different items and have gravitated to usually using a mesh baselayer. I haven’t done any testing of materials, but from a comfort perspective they have just done the best job for me.

Subjectively, I’ve noticed two main things with the mesh that seem to work. (1) The mesh structure holds the outer layers away from the skin. Other baselayers I’ve tried will certainly soak up moisture, but then they are stuck to the skin and the next layer will often stick to them. That may be the goal – to keep passing the moisture outwards. But I just don’t find it as comfortable or as easy to adjust.

(2) When you do get hot (or ideally, *before* you really get hot & sweaty), the mesh allows you to vent very quickly – just open the zippers on the outer layers and you have lots of skin exposed directly to the outside air. When I run in the winter (in these parts that means 20s and 30s) I typically just wear a mesh baselayer and a wind jacket, and adjust the jacket zipper as needed. I rarely build up any sweat. If I’m hiking instead of running, I may add a thin midlayer with a zipper to accomplish the same thing.

I know that is just subjective and anecdotal, but I can unequivocally say this approach works very well for me, and it doesn’t seem to involve “wicking” in the traditional sense, since there is so little fabric against the skin with the mesh. So it seems to circle back to the question about the conditions (either environmental or the other parts of clothing) that need to be present for a wicking approach to be effective?

[David C]

Thanks for this extremely detailed and informative article! My main take-away is that a thin, non-napped base layer with high proportion of synthetic fiber is the best place to start. This absolutely matches my experience in pretty much all conditions.

I have an observation about wool content. A small or moderate amount of wool in a base layer seems to add a lot of additional comfort across ranges of sweating and saturation when compared with pure synthetics, even if they hold more moisture. Are any of the measures from your study indicative of performance/comfort across a range of moisture levels from damp/wet to dry? Is that the moisture capacity piece Ryan mentions above in relation to wool?

I hope your future article on polyester vs. wool includes some samples of synthetics that include a lower % of wool than those marketed as full merino. Capilene Air now is something like 50/50 wool polyester.

[Stephen Seeber]

Hi Ian:  Thanks for your comments.  Concerning freezing in the outer layer, that is where pit zips for ventilation can really shine.  Of course, I don’t know how that works in the Arctic, but here in Colorado, it works well in the winter temperatures and conditions I experience.  I very seldom suffer from frost in my outer layer by using my pit zips to provide needed ventilation.

I suspect you are correct that pressure from movement, particularly movement between layers can get hard to wet layers start wicking.  There is probably a way to replicate and prove that.  The problem is that sort of motion will have unpredictable impact in the field.  I would rather use a layer that begins to wet without additional external and undependable forces.   Wetting at backpack straps or where the backpack contacts your back if no spacing is provided is definitely  an issue.  There is a lot going on here.  Those issues produce localized changes in dewpoint that can lead to condensation  because moisture simply cannot evaporate  in these locations.  The pressure in these areas can also lead to moisture transfer due to diffusion in those areas that are subject to added pressure.  Backpackers face a special challenge to avoid saturation in those areas.  I also agree that contaminants are an issue that require extra care in the use of the items you mention.

The source of heat that is powering evaporation from your layers is always a key issue.  When water is trapped in your layers and your heat production goes down, if your body is the heat source, you  are in danger of hypothermia as your body expends heat and energy to dry the trapped water.  In the summer, during high temperature, high humidity periods, if wind is powering drying a wet outer layer, your body may tend to overheat.  The sweat you are producing may well be wasted if  the latent heat of vaporization  is not removing heat from your skin.  These sorts of issues will be covered in the upcoming articles in this series.

[Stephen Seeber]

Hi Chris:  Thanks for reading and sharing your experience.   Is wicking an effective moisture management method?  That is the name of the article and that is where this series is going.  The use of mechanical ventilation, along with high MVTR clothing are things I have advocated since I  started posting on BPL.  I will have more to say on these issues in this series of articles.

[Roger Caffin]

Imho
Testing fabric as raw fabric is easy (for a given value of ‘easy’).

But testing clothing as it is used in the field by different people and under different conditions on different days is a nightmare and almost impossible. It certainly won’t be reproducible!

Cheers

[Stephen Seeber]

Hi David: Thanks for describing your experience with napped vs non-napped base layers.  Concerning wool:  I should start my wool vs polyester testing tomorrow.  I had not considered blends but given their popularity, it would make sense.

[Mike M]

^ I’ve owned a couple of 100% merino pieces, the only ones I own now are blended (I think most are in the 25-35% synthetic range)- last longer and you get some of the benefits of syn and the wool both.

[Stephen Seeber]

Mike:  Why do you prefer wool or blends to polyester?

[Mike M]

Mike:  Why do you prefer wool or blends to polyester?

I don’t :)  But if it’s going to be a long trip I’ll compromise a little and bring a merino blend base layer.  My go to base layers are the OR Echo for most 3 season stuff and Patagonia’s Thermal Weight for winter.

I still have a couple of the old Patagonia Merino 1 tops (65% merino/35% syn iirc) and will use them if the trip is going to be on the longer side.  After about three or four days syn base layers can get a little odoriferous!

[Daryl and Daryl]

Roger,

“But testing clothing as it is used in the field by different people and under different conditions on different days is a nightmare and almost impossible.”

I agree.  Been experimenting for 65 years of backpacking and every day on my 1 hour walks.

Still hopeful.  I read all the articles (go Stephen) and discussions.  Still buy new products if they sound promising.

[Scott Emmens]

Yet another mind testing, great article Stephen, thanks you. Is the Amazon Dozier sample a garment or fabric? I’ve found one listing which seems like it could be what you’ve tested https://www.amazon.com/Dozier-Textiles-Moisture-Wicking-Stretch/dp/B091G2KG37/ref=sr_1_12?crid=12PKDSAJ5Q406&keywords=dozier+textiles&qid=1641958740&sprefix=dozier+%2Caps%2C590&sr=8-12 Is this it?

[Stephen Seeber]

Hi Scott:  That is it.  Even the same color.  Are you going to make a shirt out of it?  Is so, let us know how it works out.

[Woubeir (from Europe)]

Interesting article although I would have liked that an ultralight fabric like e.g. OR’s Airvent-fabric at 78 gsm was also included.

[Paul McLaughlin]

I had – and may still have, if I dig for it – a shirt that I got from the Patagonia rep back in the early 80’s when they introduced Capilene. One half of the shirt is Capilene, the other polypro. The idea being to convince us retail shop folks how much better the capilenes was than the polypro. I could never tell any difference in warmth or wicking. The capilene sure looked better, and kept its shape better after numerous washings. Since that time I have a variety of synthetic base layers, and all seem to do the job about the same. I have some polartec Powerstretch bottoms, which I do find warmer than the lighter stuff, but I don’t really use them as a base layer, more as a light mid layer.

I’ve used merino wool base layers, and I liked the performance in terms of moisture manage ment, and I prefer them in the case where I am wearing long johns with shorts on a ski tour , with the long johns primarily acting as sunscreen; they seem to be a bit cooler in that use than the synthetics are. But too fragile for me, they do not hold up anywhere near as long as the synthetics do.

I think a key point is drying time. As Ryan has said, you are almost guaranteed to sweat at some point during your outdoor day, no matter how carefully you manage your layers. So, how fast those layers dry is very important. My favorite baselayers are currently OR Echo, and some old Terramar shirts that I have had for many years. Both work for me.

Also, I think that how these things work is very dependent on both the conditions you are in, your own metabolism, and what you are wearing on top of them. When I’m at 12,000 feet in the Sierra in a breeze, with the humidity in the teens, everything sure seems to wick really well. Different story at sea level , 90% humidity. You won’t get much wicking or drying when there is no evaporation.

[Tjaard Breeuwer]

RE: Winter use:

Stephen,

I understand your comment about not using a heavier baselayer for winter use, as the wicking performance declines, and insulation value doesn’t increase very much for the weight gain.

So that brings us to the idea of a system of:

1. Thin, wicking baselayer
2. sufficient insulation layer for your needs
3. shell

If the good baselayer is wicking moisture off your skin, then spreading it across its face, and it is evaporating there, then that moisture vapor must then pass through the insulation and the shell, right?

If that is functioning correctly, then what is the benefit of the baselayer at all?

After all, in that scenario, the outer face of the base layer is functionally the same as your skin, except moisture will evaporate more slowly, since the temperature is slightly lower.

I wonder if that is how mesh baselayers work.

Coincidently, I did do a brief, relaxed  XC ski a few days ago, wearing my Polartech Alpha Hoody directly next to skin, underneath a shell, in temps just above 0 F/ -18 C , and it was comfortable, but this was only an hour or so.

[Tjaard Breeuwer]

Re: Wool blends

 

Yes, please do test some wool blends. Several companies now make garments with the nylon core wrapped in merino.

From a wicking point of view, that would seem interesting, with the (fairly) hydrophobic nylon, surrounded by hydrophilic (but not entirely, and not homogenous) wool,

I really wonder what that results in as far as wetting, wicking and drying.

[Roger Caffin]

Thin, wicking baselayer
sufficient insulation layer for your needs
shell

Curiously, this is exactly what any experienced ski tourer does.
And we have known about this for decades.
Sadly, the knowledge dos not seem to get passed on.

Cheers

[YoPrawn]

Interesting article. Far more in-depth than I was expecting!

I personally, honestly, never really thought much about the moisture wicking aspect of base layers for my use. It always felt like an over-hyped aspect with not much real-world implications outside of the most extreme conditions. I always just used a base layer that met 3 criteria:

1. Can it stretch considerably, so that I can cram material with insulating value inside of it?

2. Does it have at least UV-15 protection for wearing in direct sunlight?

3. Does it feel nice and dry fast?

Been using an OR Echo hoodie year round, which fits all these criteria. I’ve crammed vegetation inside of it for an insulation boost. LOL (it actually works amazingly well)

[Stephen Seeber]

Hi Tjaard:  If that is functioning correctly, then what is the benefit of the baselayer at all?  I will be getting to that in article 3.   If the good baselayer is wicking moisture off your skin, then spreading it across its face, and it is evaporating there, then that moisture vapor must then pass through the insulation and the shell, right?  The evaporation from the wicking layer is the problem, winter and summer, especially if you are working hard.  This is something I will be discussing in the next article.

I like Brinje Fishnet and will also discuss other functionally similar items in the 3rd article of this series.

Isn’t Alpha Direct comfortable against your skin!  I hope you washed it afterward and then felt the fabric after it came out of the wash.  Pretty hydrophobic I’d say.  For really cold weather, I had a 2x60gsm shirt made.  20% warmer than 1 layer of 120 gsm.   Weighs nothing.  R value around .69.  Good stuff.

I will look into wool blends after testing the straight stuff.  If straight wool fares poorly compared to polyester, I don’t see how a blend can improve the situation in any way.  Stay tuned.  I can see wool providing better anti-stink performance.  However, once you wrap it with polyester fibers there is not much in contact with your skin.  Readers who use blends can weigh on on that question.

I presume you saw the results of my test of 1 version of Power Wool, which is made with the wool fiber surrounded by polyester. That is what Polartec describes in their patent.  I cannot discern that under the microscope.  Maybe I need a more power microscope. In my testing it was functionally hydrophobic despite Polartec’s claims.   If you wear that stuff as a base layer and you get good and sweaty, eventually diffusion will push moisture into it.  But, I can’t tell you how it will handle the water once it enters since I could not get any to enter.  The sweat may end up running down your pants!  I am sitting here waiting for a test to finish, and happened to have a little piece of Power Wool sitting here.  I thought I’d try another drop test.  The drop test standard calls for 50ul drops.  That will sit on Power Wool until it evaporates.  I placed a 600ul drop on Power Dry.  It sat there for 40 seconds and then wet the skin side.  It then wicked through quickly but left a considerable amount water behind.  My contention that the amount of force required to initiate wetting when in contact with the skin will not be enough to support wetting and wicking.

[Bryan Bihlmaier]

Stephen, I can’t thank you enough for all the time you spend doing this testing and writing up the results for us.  Though I suspect, as a fellow engineer/scientist, you get a lot of satisfaction and excitement from running the tests and compiling the results.

I want to share some recent experiences I’ve had with base (next-to-skin) layers that I’ve had.  I got a MHW AirMesh fleece top for Christmas, which is similar to PolarTech Alpha Direct in that it has a fairly open mesh weave, with napped fibers on the inner layer.  The AirMesh fabric uses hollow fibers – I don’t know how much that affects wicking, or if PT AD also uses hollow fibers.  Like Tjaard above, I have used it a few times now as my next-to-skin layer, even though that is not what it is designed for, and I have to say I stay more comfortable while exerting myself, and after I stop, than I have with any of the base layers I have tried (all are synthetic).

My main winter outdoor activity is backcountry skiing.  I think this activity is somewhat unique for layering systems, because it involves a fairly high exertion level going uphill (I am usually at or near my aerobic threshold for 1-2 hours at a time), then a low to moderate exertion level, with higher speeds, going downhill that can create more significant air pressure differential across air-permeable fabrics than you would experience when hiking, snowshoeing, or even running.

Earlier this season, I had a handful of trips where, while driving back home after BC skiing, even though I had taken off my outer windproof or WPB layer (“breathable” is relative!) to help dry out my inner layers, I was very cold for the entire 20-30 minute drive, with my truck’s heater on full-blast.  This occurred wearing both a mid-weight Capilene 100% polyester base layer, and a thin, older Terramar base layer (86% Coolmax polyester, 14% Spandex) that I have found wicks sweat very effectively.  Observing my base and mid-layers, they were still pretty wet (high “water in fabric” in Stephen’s nomenclature) even after skiing downhill which provides a pretty good opportunity for both evaporative and convective moisture removal.  But on the last 2 BC ski trips, plus a couple of 3-4 mile runs, I have worn the MHW AirMesh fleece as a next-to-skin base/mid-layer.  Driving home after the BC skiing trips, I was perfectly comfortable.  Feeling the AirMesh fabric when I got back to my truck (before driving), the outside face did feel damp in places, but the inside face felt perfectly dry.

Perhaps my comfort level in this case has less to do with wicking, and more to do with 1) the napped inner face provides less contact between my skin and the cool, moist outer layer of fabric, and 2) the open mesh weave allows more direct evaporation of sweat from my skin than a more typical tight-weave base layer.

This leads to the reason why I personally have stopped using wool for any outdoor clothing.  While I agree that it does feel more comfortable against the skin when wet than SOME synthetic layers (but not all), as soon as I stop moving I get chilled pretty quickly because of the high water retention capacity.  My other winter activity is mountaineering, which can involve periods of relative inactivity while climbing and especially at camp.  I’d rather wear synthetic layers that retain much less water, so they can become more dry while I’m wearing them in camp.  (You can’t dry clothing by hanging it in your tent in the winter!)

Last thing – Chris, I too have experienced some of my synthetic “base layer” running shirts clinging to me uncomfortably when they get soaked with sweat.  Similar to my above observations, I think that fabric just retains too much moisture (too hydrophilic).  On the other hand, I have used a Patagonia Capilene Cool Lightweight shirt to run and hike in many, many times and it always feels perfectly comfortable.  Maybe part of its good performance is that it is a very light-weight fabric (actual weight for my size L short-sleeved shirt is 2.6oz), so it can’t retain much moisture mass.  But it also seems to be good at both wicking moisture from my skin and allowing it to evaporate from the fabric.

[Tim Hawthorne]

I have used Alpaca for many years.  It absorbs about 8% moisture by weight versus about 30% for Merino.  Bison down, musk ox and Yak also absorb much less water than wool.  In addition, they are hollow fibers that retain more heat.

[Jon Fong / Flat Cat Gear]

Intersting, I didn’t know that alpaca fibers were hollow.  BTW posum hairs (New Zealand anyway) are also hollow.  In NZ they are often blended with Merino to create a lighter. warmer garmet.  It’s great as well as posums are pretty much a pest down there.

[Woubeir (from Europe)]

A suggestion for a future article: is there a difference in moisture management and warmth when, in colder temps, layering two (ultra)lightweight baselayers vs. wearing one thicker, heavier baselayer ?

I’ve read a study decades ago that suggests the layering approach performs better and I used that approach since then and I must say that in all those years it worked wonderfully.

[Author]

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