By The Numbers: What’s the Best Base Layer Fabric? Wool vs. Alpaca vs. Polyester

[Bryan Bihlmaier]

Since the drying time of any base layer depends almost entirely on how much water it absorbed, I think it would be good to have a section in the article discussing how much water each fabric type absorbs.
In my experience from saturating and weighing many different base layers I have owned, synthetic fabrics absorb a lot less water (as a % of their mass) than do wool. Like you Stephen, I prefer that my base layers not absorb a lot of my sweat, so I always choose the lightest weight synthetic base layers I can.

[Jeffrey J]

I’m looking forward to your article on mesh. For all the discussions of fibers, fabric properties may be the more significant factor in warmth and moisture mitigation.

[Stephen Seeber]

Hi Jeff:

For all the discussions of fibers, fabric properties may be the more significant factor in warmth and moisture mitigation.

Well put.  That is the key takeaway from this article.

[YoPrawn]

Sorry to go on a tangent here, but since MESH layers have been mentioned here, as in Brynje, I would like to add something VERY important that I find many people spreading as a bit of a myth.

Synthetic mesh layers (brynje fishnet super thermo) are not some sort of magical layer for helping keep you safe in total submersion scenarios in cold weather. (at least in my testing)

I’ve been spending the last couple weeks (years actually) testing fabrics and clothing in total submersion scenarios in cold water and how fast I can recover from them without any additional clothing or fire or anything. In my testing, the brynje polypro fishnet was absolutely NOT at all adequate for the task, and actually made the scenarios MUCH more dangerous due to the rapid cooling effect of the stored water in the mesh and the rapid evaporation from the skin in the holes. It also does not drain water any where close to as fast as my best material and must be removed to squeeze out remaining moisture, which is also tough. Even 100wt classic fleece blows away the mesh layer in a wet, cold, weather submersion scenario.

I just wanted to mention this, as I have seen it said countless times how mesh base layers can be a safety feature for such scenarios, and in my real-world testing with both polypro and nylon mesh, this is not quite true when compared to other materials and fabrics that can be used as a base layer.

I think for a mesh layer to help at all in total submersion, it would need to have truly hydrophobic mesh that can’t absorb any water at all. Woven mesh using hydrophobic yarn is not adequate. But, that would be quite uncomfortable to wear. LOL

[Paul D]

Love your articles and experimentation Stephen. Always, very informative.

[nunatak]

Interesting stuff!

Luckily personal base layer field testing is one of the easiest, most low tech things to do – the cost of acquiring a drawer full of different types is relatively low, it can be accomplished  on day hikes, the pros/cons are felt immediately.

My 2 cents: material and fit choices are seasonally/environmentally dependent, and varies with activity.

These days I wander locally year round and have just a few perfected setups.

But in my climbing days I could be ice climbing above the arctic circle (cold all the time), summiting Himalayan peaks (huge temps swings) or hanging in the summer sun on the side of El Cap for a week (warm all the time). I needed to rethink everything before each trip.

[Andrew S]

Who is this who dares the challenge the Merino cult?  Merino will not thermoregulate and keep you cool on the hottest days?  It won’t keep you warm when soaking wet?  Buying it won’t save the planet?  What is this world coming to?  Soon they’ll be saying that men’s outdoor or performance underwear (and base layer bottoms, and pants) should have a fly!!

Or to put it another way – thanks Stephan for yet more excellent research and analysis!!!

And yes, for challenging the Merino Cult, which seems all too real.  Don’t believe me?  Visit your favorite outdoor retailer and try to buy synthetic base layers, say a zip T-neck top and a bottom.  Good luck in particular if you want a bottom with a fly.  (In fact, good luck finding even a lightweight Merino bottom with a fly.)  While almost everyone who makes a base layer makes one (or many) with wool, pure synthetics are getting quite rare.  The cult is spreading too, beyond base layers and even mid layers to insulating layers.  I recently tried to find insulated shorts (with side zips, and, please forgive me, a fly) and the only thing I found meeting this simple (and fairly obvious) criteria was insulated not with down or (better yet for something I’ll sit on) synthetics, but with baffles full of wool!

Don’t get me wrong.  I’m glad Merino and other animal fibers are used by the outdoor industry.  I buy, use, and like a fair amount of such things.  But some Merino “advantages” are unsubstantiated, exaggerated, and/or simply wrong.  On the other hand, synthetics have some real advantages, and in an ideal world, it would be easy to find quality examples of both Merino, etc., and synthetics.

One huge advantage of synthetics was only touched on above, so maybe it’s helpful to add a bit.  Because base layers like Icebreaker, Smartwool, Lasting, Mons Royal, Arms of the Andes (Alpaca), Yak, and Cashmere all have a problem.  They’re scratchy.  Perhaps in theory they are not.  They all fall below the scratchiness threshold mentioned here.  But in practice, sorry, they are scratchy.  Not when you touch them in the store – your palm won’t detect scratchiness.  Maybe not even when you try them on.  But put a shirt or mid layer over that Merino T-shirt … .  Or worse, put a backpack on.  Your results may differ, but when I start moving with the shoulder straps pressing down on the Merino, I want it off.

Yak, Alpaca, and Cashmere apparently should be a lot less scratchy than Merino – at least from the Merino manufacturers I mentioned.  That’s partly due to finer fibers, as mentioned above.  But they are also claimed to have smaller scales.  Yet in my experience, Yak and Alpaca are not less, but more scratchy, and while Cashmere sweaters typically beat Merino by at least a bit, the Cashmere base layer I tried was a disaster.

My guess is that it’s due to chemical treatment which smooths over and/or removes Merino scales (and probably also reduces shrinkage).  In fact, the only sweater I can wear directly on my chest – far less scratchy than any 100% cashmere sweater I’ve tried – is a half-Cashmere, half-Merino sweater from Zegna, a company known for innovative wool processing.  (They are also known for some Merino fibers finer than any cashmere, but only in their most expensive products, so given how little I paid for this sweater, and the labeling, I very much doubt the fibers were among their 12 to 15 micron finest.)  Anyway, back to chemical treatment:  Wish the yak, alpaca, and cashmere makers would get with the program on this!

[Jerry Adams]

I don’t get flies

I make my own pants and wouldn’t think about making a fly.  It’s easy enough to pee without one.

Is this just a U.S. thing?  Are there flies in pants globally?

[Justin W]

Hi Andrew,

Fiber diameter, which in animal fibers is called micron count is the primary factor in fabric feel comfort levels, but I do think scales or lack thereof can affect it as well, but is probably secondary to micron count.  Yes, some of the “sport” Merino brands remove the scales. But…

Merino is a much more regulated industry (as to micron count) than alpaca, cashmere, etc.  This may account for why merino tends to be more comfortable on average than other animal fiber based garments.  Alpacas, cashmere goats, etc certainly can produce fibers similar to the micron count of the best merino, but the guarantee that you are actually getting that kind of micron count to all or most of the fibers in the garment is going to be much more of a crap-shoot.

Awhile back, I went through a bit of an alpaca focus. Bought a bunch of different garments (mostly sweaters, but also some gloves, hats,  socks, etc).  Most of the alpaca stuff ranges from a bit to a lot scratchier than the merino stuff I have tried, but I did find some that was comparable in comfort. Sometimes it was labeled “baby alpaca” (no reference to age of the alpaca but to micron count) and sometimes not. Again, a crap-shoot because it is far less regulated of an industry.

And on a side note, going down to Peru or the like and buying alpaca garments is even more of a crap-shoot, at least ime.  Seems like a fair amount of stuff down there is blended with acrylic to cut costs. Maybe things have changed in that regard since I’ve been (to Peru), and probably like anything with traveling to a poorer country–if you know people that know people and/or places there (i.e. “hookups”), then that can help.  And it seems like some (or a lot) of the stuff that is shipped to and sold in the US from these less materially wealthy nations, also can be questionable as to the actual fiber content depending on where and who you are buying it from.

P.S., some of the companies started to remove the scales on merino primarily to reduce shrinking via felting.  The potential downside to removing the scales is that you may reduce the insulation capacity very slightly. Whether enough to be noticed by the human body, I’m not sure?   In any case, one shouldn’t be relying on a baselayer for primary warmth anyways.

[Justin W]

YoPrawn wrote, “I just wanted to mention this, as I have seen it said countless times how mesh base layers can be a safety feature for such scenarios, and in my real-world testing with both polypro and nylon mesh, this is not quite true when compared to other materials and fabrics that can be used as a base layer.

I think for a mesh layer to help at all in total submersion, it would need to have truly hydrophobic mesh that can’t absorb any water at all. Woven mesh using hydrophobic yarn is not adequate. But, that would be quite uncomfortable to wear. LOL”

You can’t make such a garment unless you use a mono film. Anytime you have individual fibers that are woven or knitted together,  you have spaces between the fibers. The interstice spaces between the fibers are what temporarily “holds” the water besides whatever water that may or may not be held within the material itself. The more small spaces you have, the more water it will hold.  When we are talking about the fishnet type mesh, the mesh “holes” in between the yarns are too large to hold water–that is one of the benefits.  The other is that if you are using these in conjunction with a windjacket, the combo allows you to dump excess heat and moisture faster than other combos.  And, they can be fairly light weight, but that is not so much a factor to me.

Brynje makes fishnet style baselayers out of both merino and polypropylene.  I’m a little confused by the references to the polypropylene versions holding onto moisture? A simple wash and spin test will show that they hold on to very little moisture compared to many (most?) garments.  When I wash my PP fishnet, after the spin cycle, it feels almost completely dry to the touch. It is drier by weight and feel than any other garment that I wash.

There are two reasons for this.  Polypropylene is the most hydrophobic material commonly used for garments, and because of less interstices (smaller spaces) that hold water (because most of the volume is void holes that are too large to hold water).

It would be nice if some kind of coating or treatment could be made to make polypropylene less odor promoting. That is its biggest issue imo.

[Noah]

Another aspect to consider is BPA or phthalate content; to what extent is this a concern? It seems hard to judge just how sensationalized this topic is in articles like the following: https://www.cnn.com/2023/05/17/business/bpa-sports-bras-leggings/index.html

In any case, thermal paper seems to be the biggest source, and thus many recycled paper products–including toilet paper! Time to use a stainless steel backcountry bidet ;)

 

[Chris]

I’d be interested in Steven’s take on this testing report from XOskin – https://www.xoskin.us/pdf/Mid-Atlantic-Infra-Red-Report.pdf

Particularly with respect to the correlation between drying time and the amount of additional water weight retained in the garment.

[Stephen Seeber]

Hi Chris:

Is there a specific question you have that is not covered in that document?

Steve

[Chris]

I was interested if you thought the results were consistent with yours, or if the tests were not comparable.

The results in that test don’t seem to show a strong correlation between the amount of water retained in the fabric and the drying time (especially the XOskin nylon vs. XOskin polypropylene)

But I see that it was your company that did the testing for XOskin, so perhaps I am missing something?

[Stephen Seeber]

Hi Chris:

The test methods are not readily comparable.  The methods of wetting the fabrics and accounting for water loss are very different.  The methods used in the Xoskin project were not used after 2015. It is not equivalent to the saturation method employed in the above article. In the Xoskin test document, water was applied by placing two garments in a washing machine, which finished with a spin cycle. The fabrics with the most hydrophilic performance would retain the most water.  The fabrics that were most hydrophobic, such as the polypro Xoskin, would retain the least.  Also, the washing machine wetting method produced non-uniform results, so I performed the tests multiple times and used average results.

The Xoskin performance on the kettles was interesting.  If you go to the Xoskin.us website, there are videos that show drying for some of the fabrics.  In the case of two fabrics, there was more water weight present than in the Xoskin sample.  You would expect them to dry slower than Xoskin and they did. The wool fabric contained less water than Xoskin.  According to my conclusions in the article, one would expect the wool garment to dry faster.  It did not.  I suggest that the PTFE particles in the Xoskin fabric do increase the rate of drying.  However, due to the differences in the wetting process and the water accounting methods, I would not call the drying rates from the two projects comparable.

[ZY]

Great research!

I have two questions:

(1) I’ve seen claims that wool is warmer than polyester when wet. Is there experimental data to support this?

(2) How do these base layers affect the MVTR of a  jacket? Thanks!

— ZY

[Roger Caffin]

claims that wool is warmer than polyester when wet. Is there experimental data to support this?
No, for two reasons. First, the conditions are completely unknown, and second with wet clothing you are really looking at the thermal conductivity of water. I will add that polyester dries extremely fast – whereas wool can take hours to dry.

Cheers

[Stephen Seeber]

ZY:  concerning your question about jacket MVTR. The MVTR of the jacket is unchanged by underlying layers. However, the MVTR of the underlying layers will be effectively reduced by the added resistance to moisture vapor transfer imposed by the outer layer. This means that overall vapor transmission for the multiple layers will be reduced and the underlying layers will be more likely to achieve saturation. You can read more about this here.

[ZY]

Roger Caffin：Thank you for your reply. I agree with you when clothing is completely wet. If marginally wet, the wool’s fiber structure absorbs moisture internally, keeps the outer layer dry, and forms an insulating layer of trapped air.

[ZY]

Stephen Seeber: Thanks again, your posts are rewarding every time I read them.

[Jerry Adams]

I think that with wet clothing, your body heat slowly dries it out

It takes heat to evaporate that water

That’s the main reason wet clothes feel colder

Maybe wool absorbs more water than synthetic which makes it worse as an insulation

[Roger Caffin]

What Jerry says.

Ski touring, but it rained (Oz snow fields: sigh). Lycra ski tights and a fleece top. I got wet. I put on a shell and we took off, and when the rain stopped it took about 10 minutes for my synthetic clothing to be largely dry enough. It would have been several hours before a wool layer was dry enough.

Cheers

[Megan W]

Am I remembering correctly? – I thought that Stephen did a comparison of fabrics a while ago and – among other things- found that wool didn’t take longer to dry than synthetics. As long as variables like weave and thickness were taken into account.

[Roger Caffin]

A lot will depend on the fabric and its weave, but underneath all that is a key difference between natural fibres, (such as wool and cotton) and synthetics. Natural fibres absorb water into their core, and it can take a long time for that water to go away. While it is there, its evaporation is sucking heat from the wearer. That is hard physics. Common synthetics do not have this problem: all water stays on the surface, and the surface is very often hydrophobic. (‘Hydrophobic’ means the surface actively rejects contact with water.)

Wool clothing acts as a bit of a buffer, and so it can be nice to wear at home.

Cheers

[Stephen Seeber]

Hi Megan:

I have consistently found in my testing that the drying rate (grams of water per hour) is a function of the drying conditions, not the fiber.  The actual drying time is a function of how much moisture is trapped in the fabric.  A thick fabric will tend to trap more water than a thin fabric, so it will take longer to dry.  A fabric that dries fast is thin.  The thinner it is, the faster it will dry.  The amount of moisture trapped in a thick, dense fabric, whether synthetic or natural, will take a long time to dry.  However, in use, you can speed the process by shaking or squeezing water from a synthetic.  The synthetic may be treated to be hydrophilic, but the force of the bond between fiber and water is weak, and the water is easily dislodged.  This will not be the case for a natural fiber where the fiber itself is saturated and the poor spaces between the fibers are filled with water.  This is discussed in the above article as well as others in this series dealing with wicking.

[Author]

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