Testing Fabrics for Moisture Transport?

[Garrett P]

I’m prepping for building a quiet, windproof puffy. I’ll be using a breathable inner layer and Apex insulation. But for the outer fabric I want it to be as windproof as possible, still have some amount of breathability (think gore windstopper), be as lightweight as possible but also quiet. A tough list of boxes to check.

I’ve ordered a bunch of fabric swatches and samples for 1) WPB fabrics 2) softshell fabrics 3) calendared nylon/poly in various weights.

For ballparking the wind resistance, I plan on at least starting with a breath test. To pass, I ideally want to turn blue in the face before I can push any air through. Noise and weight are pretty self explanatory for testing.

But what’s the best way to ballpark the breathability? It doesn’t need to be very breathable, since it’s a static piece, but if there is any sort of moisture that does develop inside, I don’t want it to just condense on the inside of the outer shell and in the insulation. I’ve seen the “air pump” tests with the water column on YouTube, but as I understand that’s a test for air permeability, not breathability.

Can I just rubberband a fabric swatch over a glass tube with water and place it over a burner, as a pass/fail for if steam is able to escape through? I’m open to suggestions.

[Michael B]

Usually a calendared fabric on the outside accomplishes what you are requiring. What do you mean by “quiet”? I’ve never thought to complain about the noise of my puffy.    What temps?

[Garrett P]

The gold standard for what I’d call “quiet” is fleece. Anything less could be usable, though not as optimal as it could be. That’s the only reason I have polartec windbloc still on my list even though it’s heavy. Everything else is just a sliding scale of acceptability. I’ll probably throw the fabric swatches out on the snow for a bit and then try rubbing them against each other and shaking to evaluate both the “crinkle” and the “swish” characteristics.

Temps generally from 0-30deg F, with 0-20mph wind. ~1-1.5 MET activity level for several hours or up to all day.

[Garrett P]

I think this video shows a pretty simple test I could do. Rubber band the fabric over a hot liquid, then hold a piece of glass overtop to see if it fogs or if moisture just beads up on the bottom of the fabric. Since I’m not trying to get numerical values I think it should be fine: https://www.youtube.com/watch?v=nFRLWbLqKAk

[Michael B]

The membrane 15 ripstop I am using for my quilt shell seem relatively quiet compared to other calendared fabrics I’ve used (HyperD, Membrane 10 tafetta).

https://ripstopbytheroll.com/products/outdoorink-color-map

 

[Matt Dirksen]

I’d suggest looking at what reputable hunting companies sell, to determine what kinds of materials they use in their insulated outerwear. The materials are likely to be “quiet”.

Sitka and Kuiu come to mind.

 

[Stephen Seeber]

I think you want numbers rather than vapor, which are easier to compare.  Maximizing MVTR is always a good design goal.  You can do a poor man’s version of ASTM E96, the upright cup method.  It is simple and will work.    All you need is a bunch of cups or saucers.  Fill them almost all the way to the brim with water. The bigger the air space between the fabric and water, the greater will be the resistance to vapor transfer.  Cover the cup or saucer with your fabric.  A good seal is necessary.  Start with a stout rubber band and then perhaps a layer of stucco tape, that you can get from Home Depot. Weigh each assembled cup and record the weight on the cup with a marker.  Let all the cups sit for 3-4 days.  The longer the better.  Then reweigh the assembled cups.  There are two essential requirements for this test:  a water tight, air tight  seal and a scale that resolves .01 grams.  Here is a cheap scale that will do the weighing job:  https://www.amazon.com/Digital-Toprime-Precision-Platform-Features/dp/B06X6LW4V9/ref=sr_1_2_sspa?crid=1FNWB0SAKBE0M&dchild=1&keywords=precision+scale+.01g&qid=1613142832&sprefix=precision+scale+.%2Caps%2C187&sr=8-2-spons&psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUEzRUpYN1kyWDNDU0JHJmVuY3J5cHRlZElkPUEwMDc1NDc2M1NSVENNNjhaVVZaTSZlbmNyeXB0ZWRBZElkPUEwOTE0NzgwSTVVTlk4WjhHTUNEJndpZGdldE5hbWU9c3BfYXRmJmFjdGlvbj1jbGlja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ==  This scale is limited to 500 grams so you want light weight cups.  Get some 4 0z plastic water cups.  They should be short and wide.  You want the maximum exposed surface area to facilitate moisture transfer.   When you select your fabric expect a trade off between air permeability and vapor transmission.  I have looked at a few fabrics.  RSBR .75 oz, 7 denier has good mvtr and very low air permeability (2.1 CFM/Ft2).  Another decent choice might be Argon 90.  It has better MVTR but also higher air permeability of 9.35 CFM/Ft2.  So, if you anticipate being out in windy cold weather, I would opt for CFM/ft2 below 5.  Good luck with your project.

[Garrett P]

Thanks. I have a few garments from Sitka and First Lite. The Incinerator is really nice. It’s a gore-tex membrane with a light brushed poly knit face. But of course, I’m not aware of any way a DIY’er can get their hands on Goretex materials without salvaging it from other clothing. Their Stratus or Mountain series is also nice. Infinium windstopper with micro fleece exterior. The first lite garments are a little quieter but more air permeable. I sold most of them because I’d get cold sitting after several hours in 20mph+ winds when I shouldn’t have based on the temp. I’m hoping I can find something that’s close in performance/noise to a windstopper with light brushed face, but am wiling to make some sacrifices based on what’s available.

[Garrett P]

Thanks Stephen, that method makes a lot of sense and should be pretty easy to conduct, and be more accurate than what I was planning. We have equipment at work that measures moisture of content of plastic resins similarly (steams out the moisture and measures the mass change in that case).

I hadn’t noticed that RBTR lists CFM for some of its fabrics until you mentioned it above. I’ve got a bunch of samples on the way from them and can use whatever listed levels available as a reference when testing the unknown ones.

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