Moisture absorption in textiles
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Oct 1, 2007 at 12:27 pm #1225283
I have been unable to find a clear answer on this and I know there are quite a few bright minds here on BPL so let's give it a try. The questions are quite techie and people may wonder what importance it has, but I just want to know.
I've been wondering about the question what effect the fiber has on moisture absorption and drying times of fabrics.
First example: fabrics used in baselayers. Often it is assumed that cotton is useless for baselayers. But I've found quite a few studies that give another view. Not the nature of the fiber is important but the way the fabric is constructed, how heavy/thick it is, what the pore/capillary volume is. To be used in baselayers, fibers need to be hydrophilic so that moisture can spread over the fabric and can be taken up in the capillaries. So hydrophobiv fibers like polyester or polypropylene need to be rendered somewhat hydrophilic to get good wicking performance. Next to that, there's the question of the the hygroscopic properties of a fiber. Cotton absorbs 10-14% of moisture vapor, wool up to 30%, polyester up to 1%, polypropylene even less. But that's moisture vapour (to get in balance with the surrounding evironment), not water in liquid form. Up to now, I have been unable to get a clear indication whether fibers also absorb liquid water, not just moisture vapor.
So I wonder, if two shirts were being made, both constructed in exactly the same way, same knit, same thickness, …. but one made from polyester and the other from cotton, which one would absorb more (liquid) water? Or would both shirts absorb equal amounts.
I know from studies that if you take two shirts, one cotton and one polyester, and you calculate drying times, both shirts loose exactly the same amount of water in a given unit of time. The fact that cotton shirts take longer to dry, is because it absorbed more moisture than the synthetic shirt. The reason was that the cotton shirt was made from a heavier grade of fabric, was thicker and contained more volume to store water. Again, I know fabricconstruction played a role, but not if it was crucial that the shirt was made of cotton. Would the result have been the same if it was made from polyester.
All the tests I've seen who compare drying times forget to mention that the tested fabrics differ in more than just the fiber.
Again, I repeat my question, if two shirts were being made, both constructed in exactly the same way, same knit, same thickness, …. but one made from polyester and the other from cotton, which one would absorb more (liquid) water?
Second example (more or less the same): soft shell fabrics made from a nylon/spandex combination are moisture hungry while e.g. polyester with mechanical stretch take up much less water. So it is suggested that a fabric takes up water more easily because it is made from nylon and even more when it contains a certain amount of spandex. Again, I have been unable to find clear studies who confirm this. OK, polyester has a moisture regain of 0,4 to 1% nylon has a moisture regain of about 4 to 8%. Spandex has a moisture regain of 1 to 1,5%. So spandex doesn't seem to add much in absorption capacity compared to nylon. Moreover, moisture regain is about absorbing moisture vapour, not liquid water.
If you compare the surface energy (and thus the hydrophylic/hydrophobic character) of nylon 6-6 and polyester, surface tension of nylon is in fact lower than polyester (=PET) so water will spread a tiny bit easier on polyester than on nylon. For spandex I haven't found real values but knowing that spandex is a segmented polyurethane and I've noticed values from polyurethane which are higer (higher than 50 dynes/cm). So I would assume that fabrics with a minute amount of spandex perhaps could mae wetting out more easily (but is the spandex in the yarns directly exposed to water?).
Coming back to my question: would two jackets made in exactly the same way (weave, fabric, thickness, yarn construction, whatever you can think of) but differing in their fiber composition (nylon/spandex vs polyester), would they absorb equal amounts of water when exposed to rain. If not, which one would absorb more and why?
These questions are perhaps of no direct use for people but I just want to know and the information I have is a bit conflicting. so the Richard Nisleys, Roger Caffins and other bright minds, go ahead.Oct 1, 2007 at 2:09 pm #1404207Roger CaffinBPL Member
@rcaffinLocale: Wollemi & Kosciusko NPs, Europe
You are spending too much time inside: go walking!
> Often it is assumed that cotton is useless for baselayers.
This is for several reasons. One is water absorption, but another is insulating ability. They do interact too.
> But I've found quite a few studies that give another view. Not the nature of the fiber is important but the way the fabric is constructed, how heavy/thick it is, what the pore/capillary volume is.
Yes, we do get enthusiasts for natural fibres claiming that their fibres can be spun and woven to emulate the synthetics. I have seen this attempted with wool. But what happens is that you get a poor approximation to some synthetic properties, while losing the good properties of the natural fibres. Face it: the fibres are DIFFERENT, and have different applications.
> To be used in baselayers, fibers need to be hydrophilic so that moisture can spread over the fabric and can be taken up in the capillaries. So hydrophobiv fibers like polyester or polypropylene need to be rendered somewhat hydrophilic to get good wicking performance.
The key word here is 'somewhat'. You don't want the fibres *holding* too much water: passing lots through is good; holding lots is bad. Cotton and wool seem to hold onto a lot more free water, while most synthetics let it go much more readily. This is at least partly a mechanical/surface/shape property. Try wrining out a synthetic base layer vs a long-sleeve cotton T-shirt or skivvy.
> Up to now, I have been unable to get a clear indication whether fibers also absorb liquid water, not just moisture vapor.
Interesting question, and my first answer is that it does not really apply because the water is absorbed at the molecular level (which does approximate 'vapour' I guess). However, with some cotton fibres I think there may be some splitting of the fibres which allows films of water to be held inside the splits: is this 'absorbed' water?
> soft shell fabrics made from a nylon/spandex combination are moisture hungry while e.g. polyester with mechanical stretch take up much less water.
I do not *know*, but I strongly suspect that this is a function of the structure of the weave/knit, rather than being a function of absorption. The few percent absorption into the fibres won't be significant imho.
> Coming back to my question: would two jackets made in exactly the same way (weave, fabric, thickness, yarn construction, whatever you can think of) but differing in their fiber composition (nylon/spandex vs polyester), would they absorb equal amounts of water when exposed to rain.
I very much doubt it, because the fabrics would have different mechanical properties and different water holding abilities due to the differing amounts of stretch. I *Think*. But then, who would try to make to such fabrics identical: why not use each fibre to its best advantage?
CheersOct 1, 2007 at 2:23 pm #1404210Richard NisleyBPL Member
@richard295Locale: San Francisco Bay Area
Tom – You need to stop spending so much time indoors thinking. Go for a walk; read Rogers reply; go for a walk; read this reply; go for a walk; and then post "Forget I asked that". You said, “I've been wondering about the question what effect the fiber has on moisture absorption and drying times of fabrics.”
The short length answer is “very little”.
The medium length answer is that -Regain- is a fiber characteristic rather than a fabric characteristic. It is the % of dry weight that the fiber can hold in moisture. The amount of water freely held by a fabric is generally independent of fiber content and thus regain. The main fabric property which does determine the amount of water a fabric freely picks up is thickness. Further, the time that it takes a fabric to dry is directly related to the amount of water which is in the fabric initially, the more water it holds initially, the longer it takes to dry. Finally, water evaporates more rapidly from a fabric than from a water drop of equivalent volume. This is because a fabric has a greater surface area from which the water can evaporate. This is the bi-component concept that base layers like Powerstretch and Powerdry capitalize on.Oct 1, 2007 at 3:04 pm #1404216
don't worry. I spends as much time outside as I can. Been on a very nice walk this weekend and for next weekend the plans are already there and my tarptent is ready to go. The main problem will be not getting shot at (hunting season has begun over here).
No, my question is out of pure scientific interest. So please go on. I know that there are lots of other parameters which influence the usability of a fiber for a certain purpose but currently I'm just interested in the moisture absorption part.Oct 1, 2007 at 5:25 pm #1404239Mark VerberBPL Member
@verberLocale: San Francisco Bay Area
I think it would be interesting to see analysis about how various factors effect water absorption, etc… but I also think this isn't of much use since individuals can't typically specify all the factors related to how a fabric is made.
A more practical question is what are the performance characteristics of fabrics (or specific clothing items) that are actually available to us.
I have not done a systematic analysis of materials and/or construction methods -vs- absorption. I did some ad hoc testing several years with clothing I had in my closet. My motivation was that I saw numbers about absorption that seemed much lower than my field experience. So I wanted to run a semi controlled experiment to see if my perceptions from the field were way off.
I lost the raw data but wrote up my memory water retention in clothing page.Oct 1, 2007 at 9:46 pm #1404265Richard NisleyBPL Member
@richard295Locale: San Francisco Bay Area
Tom – The following data will support the summary conclusions that I posted earlier. I decided that a table of data would be less boring than addressing this topic in narrative form.
This is an easy analysis for any of the BPL forum readers to verify at home. For example, if they saturate their cotton top and their Merino wool top, which ever is thicker will absorb more water and take longer to dry.
If you want to know how different fabric materials will absorb water vapor, just use the standard ANSI Regain % for the material type. There are normally only fractional percentage differences between this average value and each vendor's value.
If you want to know how different fabric materials will absorb liquid water, just measure the thickness and extrapolate from the data in the table below.
Now everyone should know the answer to the question, "If two shirts were being made, both constructed in exactly the same way, same knit, same thickness, …. but one made from polyester and the other from cotton, which one would absorb more (liquid) water?". The answer is that THEY WOULD ABSORB APPROXIMATELY THE SAME AMOUNT OF WATER AND WOULD TAKE APPROXIMATELY THE SAME AMOUNT OF TIME TO DRY.
The specimens were not wrung out. They were placed in the atmosphere of 70F and 65% relative humidity to dry. This is the same standard environment used to determine the Regain's Wc value. The mass of each specimen was automatically recorded at appropriate intervals in the drying cycle. The time to dry was recorded when the mass of the specimen reached 105% of its dry mass.Oct 2, 2007 at 2:17 am #1404273
I agree with you that my question is perhaps not directly of real practical value to individuals who want to buy e.g. a baselayer top. You can only buy what is available.
My interest was triggered by well known claims and misconceptions e.g. cotton is bad for baselayers because it absorbs a lot of water and dries very slowly. In an experimental set up, this claim may be confirmed, but the explanation is perhaps more complex than just 'cotton absorbs a lot of water'. Such experiments, and a lot of them have been done, always take a direct path between absorbtion/drying times and cotton. Almost never, the way the fabric is constructed, yarn construction, fabric thickness are considerd in the analysis. Comparing the absorption capacity of a cotton shirt with a synthetic baselayer top that weights half as much, is like comparing appels and oranges. Concluding things out of this experiment is a bit misleading then.
thanks for your table. You actually confirmed what I already suspected. It clearly shows how other factors than just fiber content can influence the properties of clothing we're wearing. Of course, moisture is just one factor, there are lots of other factors and while moisture absorption in itself isn't perhaps a factor to stay away from cotton as a baselayer (simply said, we just need thinner, lighter cotton knits/weaves to get comparable performance as synthetics), other factors come into play that may make such light cotton fabrics very undesirable for use in baselayers. We could go further about which factors that could be and feel free to do so if you want, but for now, my question has been answered.Oct 3, 2007 at 2:26 pm #1404445Robert CBPL Member
"My interest was triggered by well known claims and misconceptions e.g. cotton is bad for baselayers because it absorbs a lot of water and dries very slowly."
I don't want to beat a dead horse, but don't forget that people don't like cotton as a baselayer, or any other layer in the backcountry mainly because it doesn't insulate when wet, whereas wool and synthetics do insulate when wet. Wool dries just as slow as cotton, maybe even slower, but people like it as a baselayer, so dryig time isn't cotton's main sticking point, imo, it's its insulating properties. Another bad thing about cotton is the fact that it becomes stinky almost as soon as you start sweating. Synthetics are slower to gather stink, especially when given special odor resistant treatments.Jan 8, 2008 at 2:00 pm #1415336Brittany WMember
Hello all, I have a question that I don't think merits its own thread so here goes.
I've always worn cotton t-shirts on warm/hot days, and have been unhappy with the long dry time. Today I went to a thrift store and looked around. There are plenty of 100% polyester shirts, and plenty of nylon/spandex blend. Also a few 100% silk. I bought a silk one (it was $1.99 so even if it's no good for hiking I at least have a nice shirt!).
Which fabric would good for hiking on a hot day? I'd like something that dries quickly, holds up well, and stinks less. Polyester seems to have the most flamboyant patterns, which is a definite plus.
Please give some advice so I know what to look for on my next thrift store outing. thanks!Jan 8, 2008 at 2:32 pm #1415340
On a hot day in the desert, cotton is very good. In the desert, a sweaty shirt will help keep you cool. In a lot of mountainous areas, a hot day can quickly turn to a very cold, windy day. At that point, a cotton shirt, being wet from sweat, is actually dangerous. Thus the phrase "cotton kills". Just about any synthetic (or wool) is better. The synthetics vary so much by their wicking properties as well as their comfort that it hard to summarize. I know Backpacker did a comparison years ago of various base layer shirts, but I don't have a link (and there may not be one as Backpacker doesn't put all their old articles on the web). At the price you mentioned, you are probably best to do just trial and error (since some preferences are personal anyway). Personally, I like the North Face shirt, but it is expensive (I got it as gift). I know a lot of people on this list are fond of wool as a base layer.Jan 8, 2008 at 3:56 pm #1415348P SMember
I spent countless hours trying and testing different baselayers for the fastest drying times and best wicking abilities.
In the end, I found your primary concerns should be 1) smell 2) smell 3) smell 4) wicking 5) drying. All the odor-repellent, or "silver thread" baselayers will eventually smell…like sometimes 10 minutes in a walk or run. And even if you wash them every time you go outside, they start to smell faster and faster.
My lesson? Go with Merino Wool.Jan 8, 2008 at 8:15 pm #1415395Frank RamosMember
There is a certain amount of truth to the statement that fabric construction/weight/thickness is more important than the fiber used to construct the fabric. However, fiber has a strong influence on what type of construction/weight/thickness is feasible.
Nylon is extremely strong for its weight and can be thus used to construct tightly woven fabrics which weigh very little but are still extremely strong. Polyester and polypropylene are slightly less strong than nylon. Cotton and wool are significantly less strong than nylon and polyester and so fabrics made from these are always thicker. So that is a strong argument in favor of synethics, even if there were no difference in moisture absorption in the fibers themselves. Garments made of synthetic fibers will weigh half or less what comparable (equal strength and durability) garments of the natural fibers weigh, and be half as thick, and thus absorb half as much water.
The lack of water absorption by polyester and polypropylene is a strong argument against those fibers, because it means they will be hard to launder. Body oils get into the fibers but can't be washed out because the fibers resist absorbing water.
So that leaves nylon as the ideal fiber for a plain shirt, in most conditions.
For a baselayer, fishnet blows everything else out of the waer, whether made of polypropylene or cotton, since dead air spaces absorb no water, neither in the non-existant fibers nor in the non-existant spaces between the non-existant fibers which compose the air spacaes in the netting. http://www.Brynje.no makes both types of fishnet, but to my knowledge only the polypro is sold here in the US (by reliable racing). Polypro fishnet is an old concept and something of a miracle even today compared to other baselayers, at least in terms of pure performance.
Also, not wringing out the fabrics makes for a bad comparison in Richard Nisley's chart, one which is weighted heavily against polypro knit, for example, even though anyone who has used polypro knit knows that it dries much faster than cotton knit could possibly dry, assuming you wring both garments out first. Under field conditions, water held in the knit matrix of knit polypro tends to drip away very quickly, which is equivalent to wringing the garment out. If Richard's test concludes that polypro and cotton knit are equivalent or that cotton is superior to polypro as far as drying time, then his test was clearly performed in a very misleading way.Jan 8, 2008 at 11:14 pm #1415408Mike WBPL Member
@skopeoLocale: British Columbia
…Jan 9, 2008 at 12:47 pm #1415472Brittany WMember
I had a similar experience to Mike a few years ago. I set out on a 5 mile day hike in warm weather wearing only a cotton t-shirt and my only extra clothing was a rain jacket. The shirt of course got damp, and the weather of course turned cold and windy. Lightning forced us to hole up under some trees for a while, and I put the rain jacket on but got pretty cold from inactivity. Needless to say I learned my lesson about brining extra layers. I was lucky that nothing worse happened.
And in response to Peter, I have a bad sense of smell so my only concern is the comfort of my fellow hikers! Maybe I shouldn't worry, hikers are supposed to stink … right?Jan 9, 2008 at 12:51 pm #1415473John S.BPL Member
Right Brittany. If you aren't stinkin' after a couple of days, you aren't doing something right ; )
While cotton might be okay on a hot day in the desert, the desert night can turn right around and be dang chilly with a huge temperature fluctuation. I personally would never wear cotton. There is no reason to when you can get quick drying supplex nylon. I went swimming (wearing pants, no shirt) on a November Arkansas hike at 5 PM and was dry in a couple of hours; dry weather, no wind, temps 60's day and 40's at night.
Consider the sun protection of wearing only a base layer of merino wool, capilene or equivalent. I think it doesn't match supplex nylon unless others have stats saying different.Jan 10, 2008 at 3:34 pm #1415634dan mchaleBPL Member
I don't think how fast something dries is the answer to everything. I don't go out when it's hot without having a cotton t-shirt in the pack. Sure, things may cool off in the evening enough that I might have to take it off because it has not dried out, but all during the day it was helping me conserve water and stay cooler. Although they may stay dry, synthetics suck the water life out of me when it's hot. When it's hot, I believe cotton creates a vapor barrier that acts much like vapor barriers used in cold weather gear. It keeps things cooler and you sweat less because the wet cotton keeps the skin moist. A synthetic is designed to stay dry. What that means is that as soon as your sweat hits it the sweat is gone and the synthetic pulls more out of you….and on and on. I'm sure if it is a hike where water must be carried, the difference in what needs to be ingested is measurable. I have been on many trips where I was sorry I forgot my cotton T. In the evening you just swap it out like any other layering change. This idea that cotton is dangerous is silly. Sure, it's dangerous for someone that does not know the ways of the outdoors, taking nothing but cotton, but beyond that it can play an important role at the hot end of the weather channel.Jan 10, 2008 at 3:53 pm #1415636
You are right, if you carry an extra (non-cotton) shirt, then it isn't dangerous at all. By the same reasoning, taking it off completely solves the problem as well. Either way, though, you wouldn't be as warm for the weight as if you wore just the single synthetic or wool base layer. I never carry an extra shirt, so my base layer better wick or I'll have to take it off (and then it is no longer my base layer).
I will also add that you have a point about synthetics and their wicking. My wife complains that some of her sports-bras (her main base layer) wick too much. I know that there are differences. For me, the North Face one I own is much more conformable than the (cheap) Thorlo shirts I own. I actually prefer the Thorlo mix (cotton/synthetic) because the straight synthetic is very plastic feeling (lots of static as well). The North Face may not wick as much (I'm still a bit sweaty) but it wicks way more than cotton (I would be drenched in a cotton shirt). I hate to make a blanket endorsement of the North Face shirt though (especially since it is expensive and I'm not completely sure that is the brand name) but I do think it is worth asking around and trying different brands (if possible). Some of them feel as comfortable as cotton but don't hold the moisture.Jan 10, 2008 at 3:57 pm #1415637Franco DarioliSpectator
@francoLocale: Gauche, CU.
That is why we often give poor advice by generalizing. Dan is right, in hot weather, the quicker the top dries the more sweat the body will produce to keep the temperature down. The longer the top remains wet, the better it works under those conditions. So cotton is the right choice for a hot and dry area, but not in an alpine environment when the temperature can change dramatically very quickly. (of course one could just take it off and put other layers on, but that is not very efficient).
At the opposite extreme, well below freezing, some also find that a vapor barrier will keep the body moist but is very efficient in trapping the heat. Here the advantage is that the sweat does not end up freezing inside your precious down bag.
The problem is that we are conditioned to want to stay dry at all costs, and that works well for the manufactures marketing divisions.
FrancoJan 10, 2008 at 4:08 pm #1415639
I agree Franco, well said.Jan 10, 2008 at 4:21 pm #1415642Richard MatthewsMember
@foodLocale: Colorado Rockies
Are you willing to compromise? When I hike in the Grand Canyon I carry an expensive custom pack, but I wear a $20 Dickies chambray long sleeve shirt. It is a cotton blend and performs almost as well as cotton during the day, and almost as well as synthetic at night.Jan 10, 2008 at 5:41 pm #1415659dan mchaleBPL Member
needed. I'm just making the point that cotton has it's place whether it be blends or whatever, and I'm trying to make the point that sweat is not all that bad. Being a little wet can be a good thing at the right time and place. I'm mostly writing this for people that don't know everything yet, that are researching – not trying to convince my peers of anything.
I'm not so sure you can get that sloppy wet, salty, clingy feel from anything but 100% cotton though. There's nothing quite like a slimmy cotton T that's been soaking it up for 7 days. :>)
Good suggestion on how to save up for a pack.
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