I just got some camo nylon rip stop fabric at walmart and was thinking of making a square tarp. I have been testng it by putting some over a cup and holding it in place with a rubber band and put sone water on the top about a tea spoon. It has not leaked threw and I can not blow air threw it. It is some what shinnny on one side. I do not think it is silnylon because it is not slippery. My question is is this stuff water proof and will it be to heavy for a 10 X 12 tarp for hiking? Like I said I am new and just learning. I only got a 3 inch wide section to test. Thanks Greg

Greg,

Your test won't provide enough water pressure to test properly.

It's probably a decent DWR, but not waterproof, IMO. However, it could be PU coated....waterproof!

Others can give a better testing recommendation than I. However, try setting up a bigger section and spray a hose at it from various distances & water pressures. Lay a towel underneath to see if there's leakage.

Shiny coating?
That is likely to be acrylic. It is not really all that waterproof. An acrylic coating is very cheap and is commonly used to help the fabric keep its shape.

However ... Have a Go!
Provided you pitch the tarp with a bit of a slope on the roof and you seam-seal the ridge somehow, it will probably work moderately well for a couple of years.
Have a Go!

Cheers