In reply to jeppuda:
Did my jacket a few weeks back and it is now as good as new.
The idea is that there are two waterproof parts to your jacket:
a) The Goretex membrane.
b) The DWR water repellancy coating that is sprayed on yor jacket in the factory. It is this stuff that makes the rain drops 'bead' on your new jacket so nicely.
The idea behind washing and treating your jacket is to:
a) Wash off the oils and dirt that are stopping the Goretex from doing it's thing.
b) Replenish the DWR coating on the outside of your jacket.
Here is how I did mine:
1) Put washer on an empty run with nothing in it, no clothes, no detergent. This will rinse the machine and ensure that there is no rogue detergent or softner in there. I understand that softner is the real evil stuff that it will wreck your jacket.
2) Put jacket in washer and wash on cold with Nikwax Tech Wash. This washes out all of the oils and dirt that inhibits breathability of the Goretex.
3) If your machine has an "extra rinse" option, use this. If there is no "extra rinse" option, put the jacket through on a full cycle again, but with no extra detergent. The point is to give the jacket a proper rinse to get all the detergent off.
4) Add "Nikwax TX Direct Wash In" liquid to the washing machine and wash the jacket again on cold, full cycle without extra rinse. The fluid is essentially the "DWR" stuff that they initally apply onto the jacket in the factory. The idea is for you to get this stuff to cover the jacket all over. I followed the instructions on the bottle, but was generous with the amount I used.
5) Once washed and covered in the DWR stuff, put the jacket into the tumble drier on low temperature for about 20-30mins. The heat of the drier will "melt" the DWR coating that you have just applied and ensure that it covers your jacket evenly. I was concerned that my jacket, being synthetic, might melt in the drier, but it didn't.
Done - good as new!
I had concerns about washing my jacket (a RAB Latok) as it was a pretty pricey investment a few years back. I didn't want it all to go horribly wrong and end up having to buy a replacement. I have to say, I'm glad I washed it.
I have done another jacket before and used the spray-on DWR stuff, but the wash-in seems to have taken better.
Iain