The post was corrupted and I haven’t been able to find a good archive of it. I pulled some text in from another page in May 2025 as a starting point, but this really needs a complete rewrite, updated references, and some corrections. I have run many tests, several of them better constructed since first posting this. I need to find that data and include it here. Maybe this will happen sometime before the end of 2025 🙂
Managing moisture is critical to comfort and safety. Heat loss when immerse water is 24 times more effective than if you are standing in still air. While a soaked garment isn’t as effective, it can chill you more than standing naked. Ideally, you want clothing to stay dry. It’s not always possible to keep clothing dry, so the best mitigation is to select clothing which minimizes water retention and dries quickly.
Polyester absorbs the least water, followed by nylon (which is a bit more durable) and then wool which has the bonus of resisting odor. There are a variety of wools including sheep (merino particularly nice, icelandic warm), goat (cashmere – luxury but very fragile), alpaca (warmest/weight), and possum (found in AU and NZ). Cotton is an inappropriate material for highly variable conditions. Cotton can absorb more than four times of its weight in water and can take five times as long to dry as some synthetics! Silk, Rayon, and a host of other fabrics are better than cotton but not great. The article why cotton kills explores this topic in more detail. There are several treatments that can be applied to these materials which make them even better at resisting water absorption such as Schoeller’s nanospheres.Â
A nice side effect of quick drying clothing is that on extended trips in the back country or when you are adventure traveling you can wash your clothing in the sink or river and be able to wear them almost immediately. This reduces the amount of clothing you need to carry without being grubby or smelly. All of my clothing normally dry overnight if spun dry or squeezed with a towel after washing. The exception is when it’s >90% humidity and <65F… some items are slightly damp after 7 hours, most most are completely dry (e.g. not even 1gram of extra weight from the water).
My experience is that water retention (called regain in the industry) is driven by three inter-related issues. The base material, the fiber (how the material is assembled into fabric), and the thickness of the fabric. For example, even though nylon absorbs 2x more water than polyester, a thin nylon woven shirt (like light weight supplex) can have the same water retention / drying properties as a knit polyster base. See the BPL thread about water absorption in textiles and look for posts by Stephen Seeber, especially is “By the Numbers” posts.
Over the years I have read people talk about how much water various materials absorb. Most of the time the numbers seemed low, so I ran some simple tests to determine how much water was absorbed by various garments that I use (which is a combination of material, fiber, and weight/thickness). Alas, I have misplaced the spreadsheet with all the results. So the following data is (1) possibly wrong because I don’t have a great memory (2) wasn’t super rigorous (3) wasn’t a pure apples to apples test. I didn’t use the same weight for each material. Rather I used the shirts I owned. The specific shirts I remember included:
Polyester: light weight powerdry
Polypro: light weight base layer (20 years old or so)
Cotton: Haines beefy-tee with a logo from my work
supplex nylon: RailRider Eco Mesh
wool: smartwool light weight tee
rayon: aloha button up shirt
bluesmith hydrophobic shirt (polyester+nanospheres)
First Test: Weight the garment, submerged it under water and kneaded it, pull it out dripping wet, weight it, squeeze everything out I could get out, weight again, wear for 30 minutes, weight again. Something that was pretty surprising is that when I did this test, the dripping weight was much higher than I expected. with the exception of the bluesmith shirt which was only 1.2x, nearly everything was at least 2x, wool being 3x, cotton 4x, and rayon 5x. After 30 minutes of wear, the figure were something like bluesmith 1.05x, polypro 1.2x, supplex 1.3x, polyester 1.3x, wool 2x, cotton was 2.5x. Not as large a difference as I would have expected.
Second Test: I concluded that the kneading the item fully submerged wasn’t a good test. It was most likely measuring void space in the garment and how easy a super saturated garment would release moisture rather than what it would absorb so I tried what I though was a more “reasonable” simulation. The real life situation I was wondering about was what would happen to my base layer after my windshirt fully wet out… how much water would be absorbed and how quickly would it dry out. The second experiment’s steps were:
- Weight the garment
- Placed it on top of a sink filled with water
- Briefly pressed it into the water repeatably for 30 minutes
- Shake item. Weight
- Squeeze. Wear 30 minutes. Weight
When I did this the number were significantly different. Polypro and polyester were less than 1.1x gain after the shake, and more or less completely dry after 30 minutes. Nylon was 2x gain after the shake, and about 1.1x weight after 30 minutes. Wool and acrylic were something like 2.5x after shake, and around 2x after 30 minutes. Cotton was 4x after the shake, 2.5x after the squeeze, and 2.4x after 30 minutes of wear. I am pretty hazy on the acrylic and rayon. My memory was the acrylic was around wool, and the rayon was worse than cotton after the squeeze, but had already surpassed cotton after 30 minutes of wearing. After one hour of wearing I hung the clothing in a location that the temp ranged between 45-50F with a relative humidity of approx 70%. Eight hours later then cotton shirt still felt wet. The wool was still damp, but reasonably comfortable.Everythng else was comfortably dry.
My personal conclusions were the that polyster / polypro didn’t absorb a lot of water. Supplex absorbed more, but was sufficiently thin without voids so it dried quickly. I was unimpressed with wool. Cotton really sucks because not only does it suck up the water, but it didn’t want to let go. This more or less matched my experience in the field.
The backpackinglight.com folks did a more rigorous field test: comfort moisture transport in wool and synthetic clothing. They found that wool took 50% longer to dry than polyester. My personal experience was that it takes longer than that, but we were using different fabrics and fabric weights than what I was using, and I believe invested more effort into having a true apples to apples comparision,
The champ will likely be nanotech clothing fabric.
