Dealing with moisture in clothing: vapor state vs liquid state

sorry for the double post, see the next one for the full text

Emile,

Assuming you are referring to a cold weather base layer to move liquid moisture off of your skin, bi-component  Power Dry is your best choice for active pursuits. The bottom component is comprised of a permanent mechanical capillary wicking layer to draw away the liquid moisture. The top component weave then spreads the liquid out for faster evaporation.

Power Stretch is better suited as a bi-component inactive cold weather base layer. The bottom component  is an insulating layer (similar to Polartec 100) that is optimized to pass moisture in vapor rather than liquid form. If you are static, your skin’s 95F temp will evaporate your insensible perspiration to vapor form. The top component is a dense flat weave for convection protection.

Regarding Merino wool, it is also a viable option for static use. For active use, once the fabric absorbs more than 15% of its weight in liquid moisture (regain value), it’s drying performance degrades significantly. The Armed Services scientists at Nattick Labs explicitly prohibit its use ( for static or active) activities by any military branch including the US Special forces.

Thank you for your answer! I didn’t know that Powerstretch was sub-obtimal for liquid transport but it does makes sense, because of the fleecy interior. Polartec says it’s a wicking fabric but I guess I’m a victim of marketing. Not so bad, I just wanted to learn what woulf be the better use of my Houdini Power Houdi (https://houdinisportswear.com/en-de/clothing/sweaters-hoodies/ms-power-houdi-225984 got it for 25$ at Winners). I just don’t get the usefulness of Powerstretch Pro, or more precisely its stretchiness (I may be wrong but my guess was stretchiness is for skin tight, liquid state system -wicking basically. I wear it on top of a merino baselayer and find it disapointing. On my legs I wear a 30% wool 70%polyestee baselayer (underarmour, hunting line; also found for cheap at Winners) on top of which I wear those quite interesting  tights (http://www.medalist.com/lib/img/thermogear_mens_performancefleece.jpg)

and the performance is very suprising. The second layer is a dense weave inside and a fleece outside. Water seems to get stuck under the second layer like in a wetsuit and this is extremely confortable under a lot of conditions. I’d like to be able to get this same performance on top

Power Grid is a variant of Power Dry that works the same as the above description for Power Dry.

Are you telling me that I should stop using merino for active use and switch to a synthetic base layer? What should I wear on top of it? My PowerstretchPro hoody or any loose fleece I got? Thank you

Emile,

There are lots of BPL forum members who love Merino wool for active use. I am not one of them nor are the scientists at Nattick Labs.  If it works for your activities; there is no need to change.

Any loose (2-3” larger girth than your base layer) fleece over your base is ideal for active wear. My lab tests show a cheap Polartec 100 provides the same insulation level as an expensive Polartec Alpha 120. For most people, this is adequate for temperatures down to freezing.

My lab tests show a cheap Polartec 300 or Thermal Pro High Loft provides equivalent warmth to Polartec Alpha 200. Combined with a good base layer this will provide adequate active insulation to -20F.

You can use your Power Stretch hoody as insulation layer if it large enough. If it fits tight, like a base layer, save it for home or around town use

For static use a conventional down or synthetic garment is ideal.

Thank you!!

I’ve seen one of your post where you refered to Powerstretch (I suppose Powerstretch Pro is about the same) as a base layer and a wicking one:

Nick – Merino wool or two versions of fleece are designed for next-to-skin wear in cool to cold temperatures; those are the Power Dry (.080″ loft) and Power Stretch (.130″ loft) materials. Either, in a hoody design, will provide excellent variable temperature regulation while backpacking and not be damaged by the pack straps. …

The key thing to remember is that you generate, on average, about 7 times the heat when backpacking as when you are taking a rest break. For times when you are active, you need only a relatively thin base layer and a wind shirt to maintain body warmth. Fleece variants such as Power Dry and Power Stretch have a thickness optimized for this function. Also the bi-component structure efficiently wicks moisture. When you are inactive, you need about 7x more insulation for the same temp. This is the scenario in which the benefits of high loft synthetics generally win out over conventional fleece (Polartec 100, 200, and 300). This is because at this level of loft requirement and above, high loft synthetics weigh less and compress smaller.

As an example, let’s assume that you are climbing over a mountain pass in a storm. A .080’ Power Dry or Merino wool, in combination with a wind shirt is keeping you warm. Now let’s assume you sit down and rest for an hour. You will need about 7 times the loft to now maintain your warmth. Let’s assume you are carrying a Patagonia pullover (.600” loft). You put it on and again are comfortable. You would need to carry a Polartec 300 jacket and Polartec 300 vest to approach the same warmth as your Patagonia pullover. The weight and pack volume would be dramatically heavier using the fleece option when inactive.

and

For purpose 1) It needs to fit tight to effectively wick moisture away from the skin. This is the reason Power Dry and Power Stretch are engineered to be very stretchy. Merino wool garments use a knit pattern to also be stretchy. Non stretch and non bi-component fabrics, such as Polartec 100, will wick moisture away from your skin 30% less effectively than Power Stretch or Power Dry. Capilene will wick well only if worn skin tight.

For purpose 2) they need to effectively evaporate water off the outside of the insulation. The bi-component nature of Power Dry and Power Stretch are designed to accomplish this. The internal buffering moisture storage of Merino wool also accomplishes this in a different fashion.

Has your opinion about Powerstretch changed?  Is it wicking or only works with vapor moisture? Thank you

Emile,

Subsequent to your referenced post, my field tests of Power Stretch provided some wicking when new but after moderate use / washings, wicking was low to non-existent.

Attached are three photos: the first picture is my moderately used Power Stretch top after being draped over a saucer with 3 large drops of water in it. The second picture is my New Power Stretch top tested the same way. The third picture is my moderately used Power Dry top tested the same way.

Power Stretch Used (notice how the water, looks white in this photo, stays on the surface)

Power Stretch New

Power Dry Used (provides dramatically better wicking than Power Stretch)

Do you think the pressure of the wearer’s skin on the inside of the fabric may help with the wicking and counteract the beading on the old Powerstretch?

I don’t think so.