I just bought 1 bolt of 60" olive drab, 1 bolt of 60" gray, and 1 bolt of 48" gray. All 3 of these appear to be treated with something - I assume for waterproofing. They are all 3 very slick and kind of shiny on both sides - there isn't a perceptible difference in the look of either side when comparing to the other. I've read about doing a blow through test to see if it is silnylon. How can I tell what these are?