I've heard of the breathing test and the water test, but I have done both of those and I'm still not sure if the cloth is silnylon or not. Is there any way I can be sure? I got it from the dollar per yard section at walmart, so I have no idea what it is for sure. It is green and has the ripstop grids and feels like it has some kind of treatment. However, it doesn't feel like my silnylon backpack, it barely lets air through when i breath hard on it, and when i put water in it and let a puddle set in it, a little water leaks through.

There's always the "backside test" ..... set two layers of it on the floor and walk briskly across it ... if you end up on your backside it is silnylon;-)

More seriously it barely lets air through when i breath hard on it, and when i put water in it and let a puddle set in it, a little water leaks through. tends to indicate that it is not silnylon, more likely calendared nylon treated with a DWR.

Edited by jcolten on 10/31/2007 10:09:55 MDT.

I vote DWR Ripstop. I got some similar in a grey but they also had a forest green at my Walmart.

TO make sure the fabrics is silicone coated, try to apply silicone seam sealer or sealant on it and let it cure. If it is easy to rub off, the fabrics is not silnylon.

I came across this when I bought a "silnylon" for a first time some years ago and made a tarp out of it. I sealed the seam, but it worn out quickly. I wondered how anyone could claim such a sealing waterproof, until i bought another silnylon with which it worked. The first fabrics simply is't real silnylon (it also leaks through the fabrics under heavy rain more than silnylon should).

I was really upset I discovered this so late, after making tarp and poncho out of the stuff and using it.