Re: [Paddlewise] Is Goretex damaged by salt?

Geruta_at_aol.com wrote:

> the reason for the current advice to rinse your goretex gear comes from the
> fact that salt attracts water (remember how the salt in your shaker becomes a
> solid mass in humid weather). if your dry gear is encrusted with salt, it will
> attract enough water to significantly dampen the outer layer of fabric. this
> wet layer will then require a higher vapor pressure inside the suit to force
> your sweat out through the goretex pores, i.e. you'll dry out more slowly.

This is just part of the reason salt on Goretex is bad news, I believe. 
See below for the rest of the story.

> this is the same reason why it is worthwhile renewing the durable water
> repellency (DWR) when it fades - you'll feel drier and more comfortable inside
> the suit but even if completely wet, or under water the goretex suit will
> still breath. the pores in the goretex are much smaller than the salt
> molecules, so that there is no way for salt to directly contaminate, clog, or
> alter the performance of the goretex membrane.

George is correct re:  the DWR:  it makes water "bead up" on the outside
of the garment, increasing the rate vapor can move through the garment.

I believe it is not true, however, that the pores in Goretex are much
smaller than salt "molecules."  Salt molecules are about the same size
as water molecules.  The micropores in Goretex are something like 10 -
100 times larger than an individual water molecule, and prevent the
passage of water droplets becuse the PTFE layer is very hydrophobic --
water hating -- so when a droplet nestles up against the layer, it can
not wick through the layer.

It is the latter which MIGHT account for any loss in waterproofness if
salt is encrusted on/in the PTFE layer -- for the reasons George states
above:  water IS attracted to salt, and the salt MIGHT form a "bridge"
through the PTFE barrier, allowing leakage.  (I'm doing a little
educated guessing here -- I did not get this from Kokatat.)

I know for sure that use on salt water seems to accelerate break down of
the DWR barrier/coating on the outside of a Goretex garment.  Only a
couple days are required on salt water, while a new/freshly treated
garment retains the "beading up" effect of the DWR for about a dozen (or
more) uses on fresh water.

Could be my use of the garments, however -- what do others find?

Oh, BTW, Robert, to renew the DWR: apply a warm iron (just at the lower
range of the steam setting) to the INSIDE of the garment (not the
seals).  This works a couple times, then you need to reapply the DWR. 
Nikwax makes a spray which works well.  Avoid Scotchgard -- it has
silicones in it.

-- 
Dave Kruger
Astoria, OR
sea kayaker/chemist
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