I have some material offered to me for sale -- they say it is Silicon Impregnated Nylon -- How do I tell the difference between regulay Nylon and Silicon Impregnated?
Thanks for any insight.

Regular isn't waterproof, sil is.

Hold a layer to your mouth and try to breathe (through your mouth). If you can breathe through it, it isn't sil, if you can't, it is.

Sil nylon has a sheen and is slicker and passes the breath test above.

Best bet for me is to order a small sample and carry it with me.

I once bought a bunch of grey ripstop from walmart that I thought was sil. It wasn't
A friend sent me a sample of the real stuff. It kind of crinkles when you bunch it.


dwr is very similar and, I think, would also pas the "breathe through" test.
I would leave over night with water ( a pocket rubber banded over a cup perhaps) No leak at all would be pass, some dripping would be fail.

HTH

Fold a piece in half, put it on the floor & step on it.

If you end up flat on your back on the floor......it's silnylon !!!!

Believe me..this works !