Breathable, moisture-wicking, but still feels like a cold wet sponge?
May 2, 2022 2:16 PM   Subscribe

Why are polyester and rayon/bamboo described as moisture-wicking and good to wear in hot weather? Please help me understand this terminology that is the opposite of my experience, so I can buy undershirts I love.

I have cotton undershirts and rayon/bamboo/spandex undershirts.

I love the way the rayon/bamboo/spandex shirts feel on my body when they are dry. I love the way they hang and their stretchiness. But when I sweat, they seem to hold onto the water. I end up with a cold, clammy layer under my shirt. For that reason, when the weather gets warm I switch to cotton under layers. When I sweat, cotton undershirts don't leave me feeling cold and clammy.

I need to buy some new undershirts and decided to look for ones that had the good characteristics of both cotton and and rayon/bamboo. But, bizarrely, the interwebs seem to think that rayon is "moisture-wicking" and good to wear when you sweat. Why is my experience exactly the opposite?

Related - when I dry my clothes in a tumble dryer, the rayon/bamboo take much longer to dry than the cotton. This matches my experience that they hold onto sweat.

Related 2 - polyester seems to be described in similar terms to rayon/bamboo. Would it be a good undershirt material for me?

Related 3 - how do hydrophobic and hydrophilic characteristics relate to these fabric qualities? Are fibers hydrophobic/philic, or are they characteristics of the weave?
posted by Winnie the Proust to Clothing, Beauty, & Fashion (10 answers total) 2 users marked this as a favorite
Most of the synthetic fabrics, including polyester and rayon (technically made from tree rather than oil) repel water, meaning you are left mired in your own sweat. They also don't allow for much airflow, meaning they're warmer to begin with.

However, because cotton absorbs water, if you're out hiking or whatever and get doused for other reasons (e.g., caught in the rain), it will hold more water and thus takes a longer time to dry, to the point of being dangerous if the temperature drops.

In short, if you're taking jaunts in the civilized world, your intuition is correct--you want to stick with cotton. If you're visiting the great outdoors, you should avoid it.
posted by praemunire at 2:29 PM on May 2, 2022 [5 favorites]

Do you use a fabric softener? They interfere with the wicking process in synthetic fabrics, because the waxy buildup blocks the capillaries between the fibers.

You might try wool (fine merino), which IMO gives a lot of the advantages of synthetics with few of the drawbacks.

Weave matters, too; some of my synthetic running shirts use one weave in the underarms and back, which tend to sweat a lot, and another weave elsewhere.

This article is a short explainer on the principles involved.
posted by brianogilvie at 2:46 PM on May 2, 2022 [3 favorites]

Response by poster: [I don't use fabric softeners.]
posted by Winnie the Proust at 2:51 PM on May 2, 2022

There are a lot of different types of rayon fibers, so you might want to experiment with other rayons or rayon blends. I think the main thing rayon has going for it is that it's usually soft. Like other plant fibers most types of rayon do hold A LOT of water and as you note, they can take forever to dry. Rayon is generally not recommended as an "outdoors" fabric because, like cotton, it doesn't keep you warm when it's wet, and it stays wet forever.

But I do actually use part-rayon undershirts in summer! I like the Uniqlo Airism line, which is a nylon/cupro (a type of rayon)/spandex blend. Even though they've got rayon in them, they're so lightweight I don't notice them holding on to sweat, and they practically come out of the washer already dry.

You might just like to try a different cotton knit or blend, though - cotton/poly or cotton/poly/spandex shirts tend to be softer and stretchier than pure cotton.
posted by mskyle at 2:58 PM on May 2, 2022 [1 favorite]

Why are polyester and rayon/bamboo described as moisture-wicking and good to wear in hot weather?

All else equal, an equivalent amount of moisture in a cotton t-shirt vs a polyester one will stay far longer in the cotton shirt than a poly one. I do some mountaineering as a hobby and have worked up massive sweats while climbing; after stopping for a break and cooling down, my poly long-sleeved, hooded sunshirt will be basically dry until I start up again. I'd be wringing out a cotton shirt (and have).

There are a bunch of parameters that will affect this, including cut of the garment and (as you identified) weave of the fabric. If you have a looser cut, with less contact on your skin, and a tighter weave to prevent wicking, you're going to trap sweat under the shirt. Tighter cut and looser weave and there's more chance for that sweat to move into the fabric which is, in fact, what you want, because then it's exposed to the air around you and will evaporate. The key is getting the moisture into the garment because if it's trapped it can't evaporate, but once it's in there it'll get sucked out because the outside air has far more carrying capacity than the air between the shirt and your body (as long as it's not too humid out). Note, too, that what you wear over it makes a huge difference too - if the moisture gets to the undershirt and then can't pass through the overshirt, welcome to damp city.

All of this is predicated, though, on exertion. If you're not climbing a mountain, cotton is just fine.

As for your related - I'm really surprised about your dryer duration for rayon; I've had exactly the opposite experience with poly, which is that they dry far faster than my cotton laundry.

At this point, I'd suggest two things: first, abandon rayon (I've always had bad experiences with it, too) and try a polyester undershirt or two. Second, if those don't work out, just stick with cotton. Cotton's great for normal day-to-day life, just don't go ride a bike race or hike in it.
posted by Special Agent Dale Cooper at 8:21 PM on May 2, 2022 [1 favorite]

I live in an area with very hot, humid summers and I love the Uniqlo Airism line mentioned above. The fabric is some sort of synthetic blend and is very soft and light-weight and does a great job of wicking moisture. I often use the Airism undershirts for hiking.

A really interesting article about the history of synthetic fibers (mostly polyester) was just posted to the blue.
posted by forkisbetter at 5:15 AM on May 3, 2022 [1 favorite]

Response by poster: I'm really surprised about your dryer duration for rayon; I've had exactly the opposite experience with poly, which is that they dry far faster than my cotton laundry.

It may be that poly and rayon behave very differently. I have some nylon items that dry super quickly. Cotton is in the middle. Rayon is super slow.

Sounds like it's time to try some polyester and maybe some Uniqlo as well, thanks all!
posted by Winnie the Proust at 6:41 AM on May 3, 2022

This short article by Ken Knapp of REI compares the pros and cons of six fabrics and concludes that two fabrics -- merino wool, and a combination of nylon and polyester -- are the most capable of wicking moisture. That said, Knapp points out
Be aware that features can vary quite a bit within each kind of fabric. Also, clothing makers can blend fabrics to achieve a difference in performance.
Anecdotally, like brianogilvie, I've also had positive experiences with merino. It doesn't hold on to moisture (or odor). YMMV, though, as with all things.
posted by virago at 9:26 AM on May 3, 2022 [1 favorite]

The dryer bit makes me think this isn't it but just in case it is helpful, the other thing that matters will be what you wear over it. Wicking means it will pick up the liquid sweat on your body and spread it out to evaporate. But that does require good air circulation around it, to evaporate that sweat and cool the shirt (thereby cooling you).
posted by Lady Li at 6:11 PM on May 3, 2022

I have had similar observations, so thanks for this question!

I went from 100% cotton, to 100% poly, back to cotton, and have settled on 50% cotton 50% poly for workout shirts. They seem to be an ok balance of wicking and not getting super heavy.
posted by bruinfan at 6:00 AM on May 6, 2022 [1 favorite]

« Older Sexual Feeling and Healing   |   Recommend me a four player RPG? Newer »
This thread is closed to new comments.