Introduction
I have decades of experience participating in vigorous outdoor activities that cause the same result: sweat-soaked base layers, wet skin, and resulting discomfort. I expect others have had similar experiences. There have been many discussions at Backpacking Light on proper layering techniques to counter this problem (see this forum thread as an example).
I find many of these techniques are often unsuccessful.
People don’t always understand how wicking layers function and how use conditions in a multilayer and even a single layer ensemble can degrade the ability of an otherwise capable fabric to move moisture from the skin to the environment.
This article will explore the factors that prevent wicking fabrics from performing their intended function.
I am going to describe general use scenarios that degrade wicking fabric function. I will provide test results that demonstrate the impacts of these general use scenarios. My goal is to provide outdoor adventurers with an understanding of why their wicking base layers may fail. This work will provide a basis for future articles in which I will discuss how to avoid the pitfalls of common layering approaches.
I will discuss the following topics in this article:
1. The most critical element of a wicking fabric is how well it allows sweat to be drawn away from the skin, converted to moisture vapor, and then transferred out of any clothing layers. This element is different from how well the fabric itself wicks. How well the fabric wicks does not determine whether you will be comfortable. The disposition of sweat to the environment depends on much more than whether a wicking fabric can absorb lots of moisture in a laboratory test.
2. Standard wicking tests usually measure how much moisture fabric absorbs (and how fast this happens). This data may be useful information but is inadequate to help the user understand what kind of performance to expect, even when the base layer performs very well in laboratory tests.
3. Wicking performance and drying rate of wicked moisture are related. But these two necessary components for wearer comfort are driven by unrelated physical processes. The best wicking fabric won’t keep you dry if the drying conditions limit evaporation. Similarly, if drying conditions are optimal, a wicking fabric may not have the capacity to keep up, resulting in possible user discomfort.
4. When your wicking layer is your outer layer, increased airspeed will substantially improve drying.
5. When your wicking layer is your outer layer, increased relative humidity will substantially degrade drying.
6. If your wicking base layer is in a multiple-layer system, drying is restricted by limited airflow and high relative humidity on the outside of the garment. The garment can reach saturation, at which point, sweat will drip out of the wicking fabric and go wherever gravity dictates.
Before plunging ahead, you may want to review the fundamentals of wicking in my last article. These concepts are important for understanding the information provided below.
About this Series
By the Numbers is a column by Backpacking Light contributor Stephen Seeber, who turns a critical eye towards fabrics and materials by testing for claims, degradation, and more.
What is wicking?
There is a vast array of literature available to describe and measure wicking. Most of it focuses on:
- How much moisture can move into a piece of fabric?
- How high can the moisture move?
- How fast can it spread?
Much of the research and most standard tests occur in a “standard environment” of 68 °F (20 °C) and 65% relative humidity (RH). Sometimes, testers apply low-level airflow over a test sample. Sometimes, testers use still air. Research and standards typically examine a single fabric, not an ensemble. These scenarios are very different from real-life use, where wind and humidity can vary widely, and a wicking fabric may be a base layer in an ensemble or the only worn layer.
There is an expansive marketing machine that talks about keeping you dry. However, is dry referring to the skin surface, the wicking layer, or the outer layers? Who knows? However, this seemingly limitless marketing machine has been delivering its message that a wicking layer next to the skin is critically important to comfort. We have grown to accept this even in the face of repeated outings that result in both wet skin and a wet wicking base layer.
In my opinion, both miss the reality of what we want our clothing choices to accomplish. I have a different goal: I want to get moisture away from my body and into the environment. My objective is dry skin and dry layers. This objective will keep us comfortable. Is a wicking layer the best way to achieve this objective? Perhaps not.
Here is the disconnect between real-life use, research/test standards, and the manufacturer’s claims: it does not matter how fast wetting starts or how much capillary capacity is present if the moisture stays in the wicking fabric.
The problem is that the absorbed and transported moisture has to dry. To dry, moisture must evaporate and then transfer through all layers to reach the environment. The drying rate of the wicking fabric somehow must match the wicking rate, and the wicking rate must match the rate at which the wearer sweats. If the drying rate does not match the wicking rate, the wetting rate, and the sweating rate, you end up with a wet wicking layer.
Unfortunately, the drying process occurs independently of the wicking process. There is no physical reason that the drying rate must match the wicking rate. It might, but there are many reasons it won’t. The physical drivers of wicking and drying are independent of one another.
Fundamentally, the design of the wicking fabric can significantly influence wicking performance. However, it may not have much impact on how fast drying occurs. That mismatch is a recipe for a wet wicking layer.
Article Library Resources: Read more Backpacking Light articles about wicking and moisture management:
How do fabrics dry?
Liquid water consists of numerous water molecules attracted to one another by cohesive forces. These molecules are in constant motion. The average rate of motion reflects the water temperature. The rate of motion for individual molecules in water will range from high to low. The distribution of the rate of motion is not uniform. Some molecules will have much higher energy levels and exhibit a higher rate of motion. When the motion of molecules exceeds a certain velocity, the energy available exceeds the cohesive force of surrounding water molecules, and the high motion/high energy molecules can escape to the atmosphere.
This process of escape is called evaporation. Evaporation occurs at the water surface (as opposed to boiling water, where molecules can escape from beneath the surface). Evaporation does not require temperatures at or above boiling, as is clear from watching a puddle disappear from the pavement during the winter.
The rate of evaporation increases by several means:
- As air pressure decreases, water molecules require less energy to escape (that is why water has a reduced boiling point at higher elevations).
- As water temperature increases, average molecular motion will increase, and more molecules will escape to the atmosphere.
- As relative humidity of the air decreases, the air can contain more water molecules, so less energy is required to support evaporation.
- As evaporation occurs, the relative humidity of the air in contact with the water surface will increase. These factors will slow evaporation. However, if the air is in motion and the relative humidity of the air flowing across the water surface is less than 100%, relative humidity at the water’s surface will remain low enough so that evaporation can continue – this is why water evaporates more rapidly in a breeze.
Generally, we cannot control the air pressure to regulate evaporation rate. However, we can readily impact the evaporation rate if we influence temperature levels or airflow for our layers or reduce relative humidity. Wicking layers cannot accomplish this. It requires a systematic approach to layering that recognizes all of these methods of promoting drying.
Our bodies typically provide heat to support evaporation from our wicking layers. If we wear wicking layers as an outer layer, the ambient air can provide additional energy to support drying. Airflow rate over a wicking layer’s exterior surface and the relative humidity of the air adjacent to the wicking layer both influence the wicking-layer drying rate. These are critical ingredients that the user must recognize to achieve drying and deliver moisture to the environment.
The impact of wind and relative humidity or drying performance
Let’s look at the results of a simple experiment to demonstrate the impact of both air velocity and relative humidity on evaporation from a wicking fabric. We conducted this experiment using our permeation kettles to perform a wick/dry test. This test is described in detail here. In this test, we measure the amounts of water wicked into a fabric, absorbed into the fabric, and evaporated from the fabric in still air and moving air (3 mph air velocity) at 25% and 65% relative humidity. The results are in Figure 1.
We will use several graphs in this format, so first, let’s explain the graph. This graph presents how much moisture enters a fabric and what happens to it afterward.
During the test, water transfers from a sponge into the test fabric. We termed the amount of water transferred into the test fabric during the test Wicking (blue vertical bar). We determine the amount of Wicking by weighing the sponge before and after the test. The weight difference is the quantity of water, in grams, that has been wicked into the fabric.
At the end of the test, the fabric will hold a certain amount of water. This quantity is Infab (orange vertical bar) on the graph. Infab means “water in the fabric.” The difference in fabric weight before and after the test determines the amount of water in the wicking fabric at the test’s end. Why is Infab important? The more water trapped in your wicking fabric, the more body heat you’ll expend attempting to dry the fabric when you stop moving. This energy expenditure can lead to chills and, if enough water is present, hypothermia. Infab can help you understand how miserable you might be once you stop generating excess heat.
Evaporation (gray bar) is the difference between Wicking and Infab. Evaporation is the amount of water that wicked into the test fabric but is not present in the fabric at the end of the test. Evaporation tells us how effectively the wicking fabric is performing.
In Figure 1, we see that with relative humidity at 25% in still air, 86 grams of water wicked into the fabric, 46 grams of water remained in the fabric at the end of the test and 40 grams of water evaporated. 47% of the wicked water evaporated during the test.
In the next set of vertical bars, we repeat the test at the same relative humidity but provide a 3 mph breeze. We can see that wicking increased, the “Infab” water reduced by 33%, and the evaporation increased by 45%.
We can readily see how increased airflow can profoundly impact the drying rate.
In the next set of vertical bars, we can see the impact of increasing the relative humidity from 25% to 60% in still air. We see that wicking has reduced. The amount of water – Infab – has increased, and evaporation has decreased from 40 to 30 grams: a 25% decrease in drying! Of course, if we increased the relative humidity to 100%, no evaporation would have occurred.
In the final set of vertical bars, we measure the impact of both elevated relative humidity and increased airflow. The wicking quantity returns to the level for still air and low humidity. However, both Infab and Evaporation performance is degraded compared to the low humidity, 3-mph airflow case.
It is clear from this simple example that increased airflow improves drying, and increased relative humidity degrades drying. This outcome is independent of fabric structure, fiber type, or chemical treatment of wicking fabrics.
The role of moisture spread and fabric thickness in drying performance
In popular discussions of wicking and academic research, reference is often made to the “spreading of moisture across the fabric to improve evaporation.” Spread rate is also an important metric and a surrogate for drying speed in some standardized tests. That is an appealing concept. We know that evaporation occurs on the water’s surface, so spreading the water will increase the surface area and improve the drying rate.
You don’t sweat a single drop at a single spot. You sweat from many pores in close proximity, and sweat can occur continuously. When one spreading drop encounters another, the spread stops at the contact area. Spreading can continue where the drops are not in contact. In the field, there is probably little surface area where drops are not in contact. We illustrate the impact of spread and contact in the video below. The video compresses about 7 minutes of drying time into 30 seconds.
For this demonstration, I apply four 50 uL drops of water to the surface of a permeation kettle. Two (on the right) are close together so that the moisture from one will contact the other as wicked water spreads. I place the other two drops where they can spread without encountering moisture.
The viewer can see the placement of the drops on the kettle surface in the video screenshot before the video starts. Immediately after the video begins, I place a wicking fabric over the drops. In real-time, moisture spreading reaches maximum size in 38 seconds. Spread stops when all the water applied to the kettle surface transfers into the fabric. The white ellipses around the drops indicate the size achieved by spreading. The drops are cool relative to surrounding surfaces due to evaporative cooling. The drops eventually diminish in size and increase in temperature until they disappear. At this point, they are dry. The size of the wet areas does not diminish until the 320-second mark. The two adjacent drops make contact in 12 seconds and reach their final size at 28 seconds. The combined surface area of the two separate drops is 722 pixels. The combined area of two adjacent drops is 586 pixels.
This observation demonstrates that spread does not maximize surface area when there are numerous close water sources. In fact, the two close drops are the last to disappear as drying occurs. I suggest that spread rate does not provide a useful surrogate for drying behavior. In real life, significant spread may not occur.
When adjacent wetting restricts moisture spread, the water volume in the thickness of the fabric increases over what it would be if spreading could occur. Evaporation (drying) occurs from the top surface of water. As evaporation proceeds, the volume of underlying water reduces as water molecules move to the surface and replace evaporated molecules. Drying appears to occur at the edges (see the video, seconds 19 to 30). This appearance of drying at the edges is probably an illusion. As the drop area loses water, the cohesive force between remaining water molecules of water causes the drop size to shrink and forces the drop to center itself over the area of greatest water volume in the thickness of the fabric. In the video, I show a plus sign (“+”) to mark the final position of the drop when it disappears.
Since the two drops on the right coalesced and had less spread than the other drops, their associated moisture volume in the underlying fabric pores increased compared to the stand-alone drops on the left. As a result, they were slower to dry. We can call this process anti-spread. As drying proceeds, the surface area diminishes, and drying occurs at a constantly slowing rate! The volume of water beneath the wet surface will strongly influence the time required to dry.
We can see that the rate of spread provides some useful information about wicking performance. However, it does not necessarily predict drying time. Spread does not reflect the volume of water associated with wicking. Suppose we have a thin and thick fabric with equal spread rates. The thin fabric will dry faster because there is less volume of water beneath the wet surface area. As we will see later, the drying rate (e.g., grams per minute) may well be the same for the light and heavy fabric and not particularly related to fabric properties. Fabric thickness and weight can both be good predictors of drying time. I’ll discuss the role of fabric thickness or density in greater detail in the next section.
What factors determine drying time?
To understand the critical factors that determine the drying time of a wicking fabric, we measured the drying times and drying rates of four different fabrics. These fabrics vary in weight, thickness, chemical treatment, and fiber composition. I only tested four fabrics, so this is not an exhaustive look at the possible range of variables. I conducted this test using saturated samples. I soaked the samples in warm water, then wrung out each sample until the fabric no longer produced water drops. The samples for a particular sample type were saturated to achieve nearly identical weight. I placed the samples on the permeation kettles and ran the wick/dry test in the usual manner for 30 minutes. I added this step to force more water into the fabric and achieve maximum saturation. Water forced into the fabric beyond saturation point would drip from the edges of the fabric where I captured it in paper towels so this water, like all water introduced into the test, could be accounted for. At the end of the test, the samples were removed and weighed. This step established how much water the fabric absorbed. I then placed the samples directly on the hot permeation kettle surfaces and allowed them to dry. Dryness was determined by plotting the average surface temperatures using the thermal imager. When the sample surface temperatures eventually increased and achieved their maximum temperatures, the fabrics were dry, and the test ended. This procedure provides drying time and calculation of the drying rate in grams per minute.
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Discussion
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Companion forum thread to: Why is my base layer soaked?
Sometimes a wet base layer just can’t be avoided. Soaked-based layers happen. Here is why it will happen to you.
Wicking is now sort of passe. All the current hype is around direct airflow through all the mid layers and base layers, and I am starting to believe the hype after trying the new systems this last year.
One interesting this about my MH Airmesh base layer is that when worn right side out, it acts as direct airflow with not needing any wicking action, but when it is turned inside out the airflow aspect is reduced and the wicking aspect is greatly amplified.
I don’t have a real BPL membership, so couldn’t read article, so sorry if my mentions were addressed in the article.
Hi Stephen, thanks for this. I think you words in the paragraph talking about Figure 3 are incorrect, you say the Black line is Dizier but in the key below the graph the Green line is the Dozier fabric?
Also, why did you determine the Dozier to be dry at about 93° in the 3 MPH test but in the still air test determine it to be dry at 102°?
Thanks, Scott
HI Scott: That is an excellent observation! The green line is Dozier. The black line is the 204 gsm fabric. I will ask if that can be corrected.
Your second question: Dry is not determined by absolute temperature. It is determined by achieving stable temperature. In the case of the 3 MPH test, additional convective cooling occurs which increases heat loss from the test surface relative to the still air test and this causes a reduction in the surface temperature, relative to the still air test.
Great article – Thank you. I’m a habitual base-layer soaker and have two questions for you:
Hi Kevin. Thanks for reading! I do not know what shirts are produced with the IVI888 fabric. The fabric was selected from a fabric library for its weight. I also have no idea how Permethrin would impact performance. Without testing, I could not say how it might impact air permeability or the level of hydrophilicity.
That could be an interesting question. High air permeability may contribute to improved drying. Higher air permeability requires larger void space. Larger void space will reduce fabric SPF rating (sun protection) and insect protection. So, a Permethrin coating could improve insect protection in a high air permeability fabric.
Kevin when it’s warm enough in PA for the mosquitoes to be whining around wouldn’t a shirt that retains moisture like a good old poly or even cotton tee be OK? I like to get wet when it’s hot. Get a little evaporative cooling going on. OTOH I guess I have seen days and hikes with big climbs where it was warm enough to sweat like a pig down lower and get soaked but when you reached enough elevation or slowed or stopped you could get really chilled by all the moisture flashing off.
Speaking of high SPF combined with high air permeability: When I’m out west at some elevation and it’s bright and sunny and warm enough during the day while working hard but cools off fast if you stop or the sun goes lower; I.E. perfect flash cooling situation or it’s shoulder season warm days – cool evenings on the east coast/mountains but still possible bug encounters I’ll wear a really light T like a MH lite T or a brynje and over that a Kuiu Tiburon Toray dot air matrix zip pullover treated with permethrin. I used to wear a Mt. Hardware Canyon Shirt but the Tiburon breaths better and weighs about half ( 5.5 oz. for a long sleeved shirt with zipper!) . The Tiburon is spf 40 and breathes just about as well as the brynje. OK that’s an exaggeration but it literally does have airholes as part of the weave and the breeze comes right on through. Still enough coverage to keep warm while working down to @ 50. YMMV. I’ve been using mine now for @ 4 years and really like it though will admit that Kuiu stuff can get pricey. It’s tough enough btw and also stretches well due to the dot-matrix weave, and no I don’t get anything for such an endorsement.
BTW stay tuned I’m working up a post about the little red devils; AKA red-bugs – AKA chiggers that hopefully will be entertaining and informative.
Also hat tip to JCH on the insect shield recommendation. Those folks have a smooth operation and it’s great having your own items professionally treated. No more DIY.
Hi Stephen – your article confirms why I struggle with my torso being either wet, or dry-ish and chilled when hiking MN during cooler months. Forty years of walking in the woods and I’ve only managed to keep my base layer from being saturated by either slowing down or dressing lightly such that a fresh breeze or dip into a cold spot immediately chills me. The most effective compromise is an arrangement of mid and outer layers that have tons of ventilation and full front zippers for air flow.
Granted, most of my clothing is low-mid priced and I miss out of the latest high tech breathable softshells that might really help, but I doubt that I can keep my back from being saturated with sweat. It’s a real conundrum.
When you are hot, the body sweats (produces excess moisture) and leaves a thin layer on the skin. The water on the skin evaporates drawing energy away from the body thereby cooling it. So, in this article, you discuss wicking the water into a substrate (material) and converting the moisture to vapor and having the vapor drawn away (calm air and in the wind).
Unless the body cools, won’t it keep producing sweat? That being said, where is the cooling coming from then? It would imply conductive heat transfer through the fibers back to the body and a wicking material?
Jon: Sorry, I am not following what you are asking. Is you question based on the single sentence you cite or the various concepts discussed in the article? Please give me a little more to respond to.
The body is trying to stay cool, what is the mechanism for cooling and how does it relate to wicking and evaporation? The evaporation of water is a tremendous way to getting rid of energy. Where is this transition occurring in a layered system? Does that make sense?
@OBX Hiker – Ha! I’m now done hiking in PA until October because of the bugs and heat and humidity. I’ve got an August trip planned to the Whites, but that’s it during the summer. I had Insect Shield treat my clothing because of ticks, not mosquitos. I had 5 nasty tick bites in one day in the middle of April. The first day started with temps in the upper 30’s and some freezing rain. The next day was sunny and hit the mid-60’s. We had just finished a 2-mile uphill and my shirt was soaked. I took it off and my buddies immediately noticed the ticks – they were big meat-eaters. So – I’m looking for the most breathable or wicking shirt that can be treated!
Jon:
The body is trying to stay cool, what is the mechanism for cooling and how does it relate to wicking and evaporation? The evaporation of water is a tremendous way to getting rid of energy. Where is this transition occurring in a layered system? Does that make sense?
That is not really what the article is about. This article discusses how a base layer fails to a point where the situation you allude to will be likely to occur. I agree with where you are going. The most effective place for sweat to evaporate is on the skin. The farther that evaporation occurs from the skin, the less effective evaporation and therefore cooling will be. I have stated this in a number of my prior articles. This article does not discuss the role of wicking layers in heat balance specifically. However, the concepts discussed here describe why a wicking layer fails to perform. After all, if the wicking layer is saturated, it is not drying and it is not supporting evaporative cooling. One of the best ways to waste water, in my opinion, is to wear clothing that do not promote effective evaporate cooling from the skin. Heat balance is a complicated mix of clothing choices, exertion level and environmental conditions. This article, among other things, illustrates what can happen with your base layer wicking and drying by varying several of the factors that will ultimately impact heat balance one way or another–too hot or too cold. Either can result from failed base layer performance.
Hi Kevin: Having spent years mountain biking in PA I can sympathize. I really hate the stench of deet! I would apply it every day. It worked generally, but I still came home with ticks periodically. I recommend you move to Colorado. Ticks are supposed to be here but I have not seen one yet. I am working towards a summer layering solution but its pretty early in what I am doing. One of the higher air perm shirts I have tested is Montbell cool. It is not high enough in my opinion, but far higher than most light fabrics, including perennial favorites like OR Echo, which is considerably lower. How well will any insect repellent will remain attached to a fiber that is sweated on, rubbed on vegetation and rock, rained on and washed? I don’t know, but to start, I would get the highest air permeability shirt you can find and spray it and see what happens. Can’t be any worse than what you are already doing. Here is an interesting article.
@Stephen – Thanks for the article…Instead of buying permethrin this year to treat my clothes, I “sucked it up” and sent them to Insect Shield. It was surprisingly easy. I treated my liner socks, outer socks, pants, and shirts. I don’t bother with other bug repellant – I try hard to avoid hiking when bugs are a problem, but the ticks come out much earlier in the spring than the other biting insects. It might be a bit neurotic, but my biggest fear with ticks is always them getting into a spot I can’t see or reach. I don’t worry about them on, for example, my bare arms.
@crashedagain
Interesting that you mention Montbell’s Cool line. My kid loves their MB Cool 1/4 Zip in hot desert hiking conditions and I find my MB Cool Hoody to be absolutely miserable in the same conditions. There are a few differences:
Would you take a guess about which of those factors is most significant regarding my perception that the Cool line is miserably hot? I hadn’t ever considered #3 but now I’m thinking that might be significant.
Hi Matthew:
Congratulations on raising a kid who never complains in the face of adversity. Perhaps you can share parenting tips with the rest of us.
I find that skin tight in hot weather is a poor choice. A light weight fabric will simply reach saturation faster because there will be less convective cooling in low wind, high humidity conditions. In those weather conditions, I find that a loose shirt is more comfortable because air can blow through more freely and circulate between fabric and skin. So, I would think your loose shirt could be too your advantage. A dark gray shirt might absorb more solar gain and produce higher shirt surface temperatures than a brightly colored shirt. I have actually measured this impact at our high elevations here and it is significant. I try to wear the lightest colored shirts in the summer. If it is shaded on your summer hikes, you can discount this issue. The double layer of fabric forming the will locally reduce reduce air permeability and probably add a little thermal resistance, depending on how much air is trapped by the second layer.
There is a chance, the fabrics are not the same. You want high air permeability in your summer layer. It is possible the air permeabilities are different.  Go to the Montbell website and look up each shirt. For some of these shirts they list the fabric weight. If yours is heavier, that would likely mean lower air permeability. I just did that, and the 1/4 zip and hoody versions are both 98 gsm fabric, so, if those are what you have, perhaps not the answer. Another approach would be to tape each shirt on a window with bright light showing through it. Look carefully at each and try to see which is letting more light through. This is a rough measurement of porosity. It is best done with a backlit microscope image and Photoshop to measure the bright spot frequency. If there is a significant difference in air permeability, you may see it just using the window test. If all else fails, you could call Montbell and ask if the fabrics are different. Right now, the Montbell Cool that I have has the highest air permeability of all the light weight base layer shirts I have tested. It also uses a complex fiber shape that will improve moisture management, along the lines of Cool Max fibers. It has a higher fiber count than an OR Echo, which means more capillary capacity. That does not mean that it keeps me comfortable as an only layer in hot conditions–it will get saturated in use despite its superior performance. It may be better than other fabrics, but no panacea. Finally, it is possible, perhaps likely, that your metabolism, exertion and fitness levels are different than your son’s. These differences can contribute to your different comfort levels. If you are really curious if the fabrics are different and cannot get a satisfactory answer, you can send me the shirts and I will measure the porosity and air permeability. Then we will know for sure. This is actually I question I have wondered about when I view the wide array of “Cool” shirts they have on the website.
Thank you for the detailed answer. 🙂
I have a shirt that works well for me (Patagonia Tropic Comfort Hoody) so it was really just out of curiosity. I like the TC Hoody so much I have three of them.
I saw that Montbell lists the shirts as having the same weight. I’m going to guess it’s the color of the shirt.
My kid is capable of complaining. They are actually a young adult and away at college now but I do think many useful lessons have been learned through hiking and backpacking long distances. Perhaps we can discuss that in another thread at some point.
Hi Matthew:
Was in Boulder so I stopped at REI and purchased a Capilene Cool Long Sleeve. It appears that the Tropical comfort is discontinued. The fabric is the same weight: 3.7 osy or 125 gsm. 25% heavier than Montbell Cool. I would guess the fabric is the same as what you are wearing. I measured the air permeability to be 191 CMF/Ft2., which is less than half the air perm of the Montbell Cool. Also lower than OR Echo. I will be returning this, so I won’t measure its wicking performance. It should wick fine, but because of the the light weight fabric it will probably saturate pretty fast under high exertion or high heat/high humidity. My expectation would be that this shirt will be less comfortable than Montbell in summer conditions, but you have concluded otherwise. Go figure. Perhaps you can bring both along on a hike and see how they compare under similar conditions. I wonder if the chemical treatments used by Patagonia vs Montbell have some impact on comfort. The fabric on the Patagonia feels softer and smoother than the Montbell. Some of that is probably the tighter knit of the Patagonia. Also, Patagonia uses a miDori bioSoft chemical coating, which is designed to produce a soft, smooth hand, which this shirt has. The Montbell Cool has a rougher surface feel which is, in part due to the knit texture of the shirt. Of course, my Montbell Cool has been washed many times, so, this comparison may not be comparable with a brand new shirt. So, do some comparison wearing and see what you can conclude. Tomorrow, I will return the Patagonia and keep looking for higher air permeability shirts for summer use.
Great article, thank you. If you happen to come across any other shirts that are XXL and more breathable than the Echo please let me know as I that is where I am stuck. Thank you.
great article again, thanks
I wonder where the water goes when it gets fabric wet?
Does it get absorbed into the fibers?
Or are there little micro water drops wetting the outside of the fibers and between the fibers?
Your surface temperature is like 90F. That would be a warm condition where evaporative cooling is a good thing. I’m more worried about cold temperatures. I guess that’s the surface temperature of the wicking layer which is something like that when it’s cold outside.
When I’m cold, if there’s evaporative cooling from the wicking layer, that will make me cold. I wonder how much. How does that compare to wearing more or less insulation.
Hi Brett:
Thanks for reading. I will be looking, so I will let you know.
Hi Jerry:
Where does the water go? When the base layer reaches saturation, it will stop wicking. At that point, you skin will become increasingly wet. Some of that water will be forced by diffusion into the saturated fabric. Since it cannot hold more, the added moisture will tend to drip out and go where gravity dictates. Depending on the garment fit, some water may simply drip down the skin, again to where ever gravity sends it.
If it is cold and you are sweating, you are not in equilibrium with heat loss through your garments to the environment. This may be because you have too much clothing on or you increased your activity level by, for example, going up hill too fast. Evaporative cooling is the mechanism that is designed to cool you. If it works properly, meaning your clothes can transfer vapor to the environment, you won’t trap moisture in your layers and you might be able to achieve thermal balance. If your clothes do not let vapor escape, then, water will build up in your layers, the thermal insulation value of your layers drops due to trapped water and, when you stop your activity, you may well feel cold.
The fact is, with properly functioning layers that can eliminate vapor, you maintain a broader range of cold weather exertion than if your layers just absorbed moisture without an ability to dry and pass vapor through to the environment.
and, remove insulation so you don’t overheat and sweat
if you’re sweating, you have too much insulation on
well known knowledge by experts
Well, in cold weather, a very significant amount of moisture control has to do with layer management. Climbing a step grade? Better remove some layers. Stopping for a break? Wait a bit and add layers. IMO , fabrics are great but layer management is fundamental (difficult to do right but imperative).
Added this snippet that I found on the interweb.
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