Polartec Aircore – a brief review

Hi Jerry:  The normal test can stretch the fabric and open the pores.  Not a little bit.  A lot.  That I why I stopped the test when I did.  I feared the very stretchy fabric would burst.  This makes a mess and leaves a hole in the garment.  I agree with you.  The use of a well-specified restraint could make the test more useful.  Unfortunately, we can’t order the industry to change its test procedure and we cannot order marketers to use one standard or the other.  We cannot even order marketers to clearly tell us when a restraint was used and at what pressure a non-restrained sample burst.

There are several standards for hydrostatic head testing.  Iso 811 calls for device that measure up to either 1000 mm wc or 2000 mm wc.  Clearly, this standard was not designed for fabrics produced today, which can achieve far greater hydrostatic heads. AATC  127-2018 imposes no qualifications on the limits of the test instrument.  AATC 208-2017 allows for the use of restraints with the same instrument described in 127-2018.  The purpose of the restraint is “to prevent fabric deformation”. The restraint is specified as follows: Restraint: 200 × 200 ± 10 mm, made of 6.0 ± 0.5 mm thick clear cast
acrylic. Other restraint materials may be used with the agreement of all parties. The test works by placing the fabric on the clamping surface of the tester.  A paper towel is placed on the fabric to be tested. The restraint is placed on the paper towel.  The clamp applies pressure to the fabric, paper towel, and restraint.

As you can see this method allows no expansion to the fabric. Therefore, it can withstand far higher pressures before leaks occur in the test fabric. The standard states the following: The results obtained by this method may not be the same as those obtained by the AATCC methods for resistance to rain or water spray. Results may not be the same as those obtained by hydrostatic water resistance testing without a restraint.

As permitted by the standard, I use a restraint that is a metal grid.  This permits greater fabric deformation. It is not something I often use because the results will vary substantially from a test conducted without restraint.

Here is the problem: For years, there has been discussion about the amount of hydrostatic pressure required for waterproofness. This discussion refers to values generated without restraint and the fabric permitted to expand without limit.  It is therefore very confusing when a manufacturer, like Polartec, quotes the results from a restrained test without stating that the test is performed with restraint. In the podcast, there is no mention that the test was restrained. Yet, they claim the result, as I recall, is 5,000 mmwc.  Maybe it would survive an unrestrained test to reach 5000. Maybe it would burst. We don’t know.  So, we cannot really compare the test results quoted here with our expected performance for a fabric that passes at a similar pressure, but without restraint.

We can’t change the test procedure. We must be aware of the test’s shortcomings. That is our responsibility. We can expect the test method to be accurately disclosed.  We can expect a manufacturer to identify when a restrained test result is provided and state that this value has little relationship to that of a non-restrained test.

I would like to see a shower test, such as the one I created for the Paramo article, used in conjunction with a hydrostatic head test.  Then, we would know if a fabric could withstand heavy rain, and we would know how much pressure a fabric would resist when in direct contact with water, such as sitting in water or kneeling on a tent fabric.

Hi  Jerry: What you describe is how I created my rain test.  It is described in the Paramo article.  I think it is helpful to know how a fabric responds to actual pressure when in contact with water.  What happens when you slide down snow or kneel on your tent floor could be determined with a restrained HH test. How readily can a pack strap push water through your jacket? I don’t recall the specifics of what I learned when I explored this topic a few years ago. I was trying to verify a high HH value on a 7 or 10 denier rain paint. I then proceeded to blow a hole in some Montbell waterproof pants.  I found the specified restraint to be unworkable, so I opted for a wire grid.  This doesn’t come up much for me but I have put holes in other fabrics.  I am very careful with complete garments.

My XXL is reasonably snug.  When I was doing the testing, I also purchased another Castelli jacket that used a different Polartec fabric that was lighter with less bulk than the Aircore with all kinds of confident claims about great breathability.  I purchased an XL in that.  I had to muster a fair amount of force just to get the sleeves on.  They make a XXXL in that jacket.  That might have fit. It was 4 or 5 ounces and folded small enough to fit into a bike jersey back pocket.  Holy grail stuff!  Unfortunately, its MVTR was quite a bit less.  It came out at 2160 g/M2/24hr.  So, I rejected it.

What I wonder about now is the following: Would the MVTR of a tight jacket be higher than a looser jacket?  My thinking is maybe. The vapor pressure difference that drives the moisture away from the skin would be at its absolute maximum without the dilution of air circulating between the skin and the membrane, especially if you wore it with a mesh right below the jacket.

Hi Tijaard:  The only benefit the new membrane offers over Neoshell is no PFAS chemicals.  I guess that is an accomplishment.  As it happens, Pearl Izumi has its 2024 Neoshell cycling rain jacket on sale (I think all US Neoshell jackets will soon be on sale). I purchased one. Its MVTR is 3360 vs 2880 for Aircore. Not a big difference, but not progress. It is an XL, but a more generous cut than the Aircore.  It too has stretch, but not as much as Aircore.  It does not need as much. The Neoshell jacket weighs 1 oz more. However, the Neoshell jacket has a more water-resistant main zip.  All seams are sealed. Only the shoulder seams are sealed on the Aircore jacket. I have not measured its HH, but I have never tested an electrospun with HH less than 9800.  So, the Neoshell is built as a real waterproof rain jacket. It may delaminate in a few years, but, of course, we don’t yet know how well the new shell fabric will hold up.

The real problem with these jackets is that they are used for cycling. Cycling is a high-aerobic, high-MET activity. If the temperature is above 45F it is too warm for a training effort in the Aircore jacket. I have not ridden in the Neoshell jacket yet, but I doubt it will be very different. Using this in the rain, where it may be impractical to open the zips, means you will be soaked from sweat. If the temperature is above 55F and it is raining, I am more comfortable just getting wet.  The MVTR for this type of jacket probably makes little difference unless you slow way down in the rain (which is probably not a bad idea). Fortunately, in Colorado, a biking rain jacket is seldom needed. Whichever jacket I decide to use, along with the OR jacket I use for skinning, will be taken to the local gear repair shop, where I will have forearm-to-bicep 2-way Aquaguard zips added to eliminate the issue of soaked base-layer sleeves and soaked backer fabric in the jacket sleeves. High MVTR is nice to have, but for high MET activities, ventilation trumps all other solutions.