Soft Shell Mystery
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Beth Correira
(Beth) - F

Locale: Beautiful New England!
Soft Shell Mystery on 12/06/2006 11:53:04 MST Print View

I have been perplexed by something for years. Can someone tell me why some fabrics feel colder on than others. Case in point:

Powerstretch (Marmot) vs powershield (Gamma SV). Same thickness and fleece backing near the skin but even at room temp w/little movement, I feel cold in the powershield jacket. Not so with powerstretch.

Powershield (Gamma SV) vs Powershield Lt (Golite Momentum). The PS Lt is nearly 8 oz lighter than PS but I find it significantly warmer.

Polyester windshell (Sporthill) vs Nylon windshell (Houdini). Put on the Houdini and it feels warm agains the skin but put on the Sporthill and it feels cold.

Driclime vs Shoeller Dynamic shell with a nearly identical liner to the Driclime. Driclime warm even with little movement. Very cold with the S. Dynamic.

Why does this happen?

Christopher Chupka
(FatTexan) - M

Locale: NTX
Re: Soft Shell Mystery on 12/07/2006 07:25:11 MST Print View

I love my Ibex Icefall, I the women's version is the Cirque.

A very light wool lining gives it a very broad temp range warmth.

Very comfortable with a decent amount of stretch, I usually leave it on 24/7 when in the mountains even sleeping in it.

My wife always makes me wash it when I get back because it gets "that smell".

Richard Nisley
(richard295) - M

Locale: San Francisco Bay Area
Re: Soft Shell Mystery on 12/07/2006 11:58:23 MST Print View

SIMPLE EXPLANATION - If the fabric surface is smooth, it will feel cool and if the fabric surface is rough, it will feel warm.

DETAILED EXPLANATION - Fiber deformation is proportional to the 3rd power of the fiber length and indirectly proportional to the 4th power of its diameter. That is why the micro-fiber fabrics, even if the protruding fibers are short, deform easily under pressure to a certain extent and partially copy the acting body. Thus, the contact area is always large, the amount of heat taken away form the contacting body is high and the contact feeling is cool, in spite of the smooth and pleasantly soft surface. Similar phenomenon appears after the enzymatic or chemical treatment of fabrics: this relatively drastic action results in the disintegration of the fiber ending into several fine micro-fibrils, which behave as micro-fibers.

If the surface fabric is coarse or is an axial curled fine fiber it will feel warm to you. Animal hairs, even if long, provide a warm and smooth feeling because the animal hairs are frequently curly, and their endings are tapered. Coarse surface fibers, do to their relatively low flexibility, may scratch the skin of sensitive folks. Vlad’s wool forum posts address this phenomenon (smile).

Any mechanical treating of fabrics, like brushing or carding, brings the warmer feeling. This is because the original compact and smooth plane surface of dense woven fabrics with high mass and hence high thermal capacity is being replaced by the irregular surface featuring lower mass, irregular thickness of a structure composed of some soft and easily deformed fibers. Some surface fibers are not split, and due to their relatively large diameter and short length they do not bend easily under pressure, thus conserving the surface less compressible, but full of thermal insulating air pores of low thermal absorptivity.

Edited by richard295 on 12/07/2006 12:39:35 MST.

paul johnson
(pj) - F

Locale: LazyBoy in my Den - miss the forest
Re: Re: Soft Shell Mystery on 12/07/2006 12:27:33 MST Print View

>>"Fiber deformation is proportional to the 3rd power of the fiber length and indirectly proportional to the 4th power of its diameter."

Sure,...i knew that! NOT!!!


WOW!!!

Richard, i just love reading your Posts. They are always so informative. Thanks for taking the time to post.

Edited by pj on 12/07/2006 14:08:49 MST.

Beth Correira
(Beth) - F

Locale: Beautiful New England!
Soft Shell Mystery on 12/07/2006 13:27:39 MST Print View

Thank you Richard for the excellent post regarding the science behind textiles and how they feel to the wearer. Your commentary on microfibers is spot on. The "coolest" feeling jacket I own is the windshell made by Sporthill which just happens to be constructed of polyester microfiber.

Roman Dial
(romandial) - F - M

Locale: packrafting NZ
Re: Soft Shell Mystery on 12/07/2006 22:03:10 MST Print View

Yea Richard, your answer is good -- boundary layer -- same reason alpine plants have fuzzy leaves?

christian madsen
(sherpachris) - F

Locale: SoCal
Ultralight measurement tools on 12/07/2006 22:29:27 MST Print View

Great Post Richard! Thank you for the explanation. I once figured that my obsession with pack-weight grams was enough to gain entry into the Ultralight Community. I now see that it is time to toss out my digital postal scale and invest in a good micrometer.