Date:         Wed, 30 Nov 94 10:08:32 PDT
Sender:       Vanagon Mailing List <vanagon@vanagon.com>
From:         puusital@mv.us.adobe.com
Subject:      Re: Waterproofing Canvas A No-No

>Someone here on the list explained last summer how spraying on water
>repellents on the canvass is a real no no and will make the canvas
>unbreathable and that the canvass is naturally water repellent. 

>This will cause moisture to build up in there since waterproofing will make
>the water hard to get out through the canvass.

>I have sprayed my canvass with water repellent and now it gets clammy up
>there and I wished I hadn't. Canvass is naturally waterprooof, according to
>last summer's post.

The stuff I used on the canvas is called Techtron, and it's designed to 
replenish the Durable Water Repellents (DWRs) applied to breathable waterproof 
fabrics that wears off with repeated washings. I've used the stuff on my 
Patagonia shell jacket and it definitely still breathes, so unless Techtron 
interacts with canvas in a radically different fashion than with synthetics, I 
think I'm ok. I certainly haven't noticed any increase in clammyness or 
condensation inside the bus. For short periods of rain or heavy dew, the 
Techtron will bead about 99% of the water away from the surface of the canvas.

I agree that taut canvas is naturally water repellent in the sense that rain can 
fall on it without the canvas dripping on you. However, the canvas is getting 
wet and soaking up water and when it is in this state, anything that touches it 
- like your sleeping bag in the top bunk - will cause the canvas to leak 
profusely at the point of contact.

Paul