[Diy_efi] way off topic - waterproof technology

[Adam Wade]

--- Ernest Buckler <ebuckler at icehouse.net> wrote:

>> Doesn't pass air.  DOES pass water vapor.  Two
>> failures to meet the requirements listed.

> Wait a minnit...!   I thought GoreTex was a rainsuit
> material?

Yes, it is (although it does a spectacularly lousy job
of "breathing").  It is designed to be permeable to
water vapor and wind-resistant, as I mentioned above,
both things you want from rain gear.

> Supposed to keep big molecules, i.e.RAIN, i.e. water

H2O is a pretty small molecule.  It's basically
Teflon, which increases the surface tension on water
droplets so that a droplet can't break up into
individual water molecules which then "wet" the outer
fabric, as well as plugging the perforations in the
Gore-Tex.

> and let little molecules, i.e.air, pass through.

"Air" is a large collection of various compounds, and
many of them are larger than an H20 molecule; further,
if H2O wouldn't come through at all, it wouldn't be
breathable.

Further, to keep oil contamination from killing the
waterproofness and breathability of Gore-Tex, they add
a polyurethane layer, which can only be penetrated via
osmosis (thus the lack of useful breathability).  This
is completely wind-proof.  In fact, there are versions
of Gore-Tex sold specifically to be used as a wind
break layer on hiking outer shells and such.

> Guess I better not buy that GoreTex riding jacket
> I've had my eye on, eh.

I just wrote a 5k word technical article on waterproof
technologies for a motorcycle magazine.  Short story
-- Gore-Tex is overpriced and does not do a decent job
at venting water vapor.  You'd do as well using a
plain polyurethane-coated nylon rain suit.  If you
want what Gore-Tex promises, you'll need something
made with eVent.  Unfortunately, there is not
currently any street gear using eVent, only two
off-road riding suits (one from Moose Industries and
one from Fox).  The transition might happen more
quickly if people bug the companies that make
all-weather street riding gear to use it.  Also, get
yourself appropriate products for washing and treating
the outer fabric from NikWax.  Non-toxic, water-based
delivery system, no aerosols, no environmental or
health issues like ScotchGard has, and using their
special washing products can often be enough to
revitalized waterproof garments without further
treatment.

Email me off-list and I will send you the article if
you like.  There's also a sidebar on the significant
health and environmental issues regarding the
production and disposal of Gore-Tex and eVent, and the
very immediate health hazard of ScotchGard, and
another on the physics behind waterproofing.

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