spray on or wash in?

If your garment has a wicking lining, spray on is best. Id say spray on is best if the garment is at all complicated. If you have a simple shell, like a wind shirt, pants, etc, then wash-in is effective and economical– you can do several garments at the same time. I've used the Nikwax TX Direct wash-in DWR and it reminded me of dilute PVA glue. I did a batch of a single layer anorak wind shell, a rain parka and a pair of runner's wind pants and it worked well on all.

All the DWR does is to make the water bead up and roll off rather than soak in. With a technology like Gore-Tex, it can't pass vapor if the supporting fabric gets wetted through. I don't think wash-in has that much effect on breathability– I'm going on my limited experience with it.

As working in a store I like to call suppliers from time to time to ask them difficult questions. :D

One supplier of DWR stuf of whom i had the idea he actually knew what he was talking about told me they meassured a 0.5% difference in breathability between spray on and wash in.

I'd say save yourself the effort and use the wash in stuff

Eins

thanks for the advice.

0.5% is surprisingly low, but good to know.

and maybe it's not all bad to have a dwr on the inside. a garment could just as easily wet-out from the inside (or is that wet-in?).