I posted this in another thread, but now that I have tried it I want to start its own thread. It describes mixing pure silicon caulking with Naphtha to make a liquid waterproofing that can be applied to sheets, and presumably other fabrics to make them waterproof. I tried it and it seems to work. I put it over a part of my stacks, and after a good rain it is dry underneath, and it holds water as you can se from the second pic.