Vinegar has water in it. don’t use it. Glacial stuff is the same but should be around 99.5% pure acid. It is a byproduct of a normal silicone/h2o reaction. I am not sure that it does much for adhesion, but I would be willing to try it. I would *guess* it slows down the reaction giving the mix more time to flow and penetrate fabric fibers.Unfortunately, I don’t have access to my lab since I retired some 8-9 years ago and cannot test this.
Mineral spirits is *also* not compatible with silicone caulk. After mixing (one of the reasons for the long mixing time) it actually forms a colloid. The caulk actually requires a bit of water from the atmosphere to set. So, until this happens, it will not. White Gas also works but evaporates quicker…good in cooler weather.
I am unsure what would happen with a PU coating. IFF it has only one side coated, then it should work. I had an old tent that I coated that apparently had a PU coating on one side. IFF the caulk sticks, it will be fine. Try a small dab, let it set a couple days and try to peel it off.
As far as adhesion goes, if a film is less strong than the bond, it will stay pretty much intact. If the film is stronger than the bond, it will peel. One of the reasons for using thin layers (2-3 max) of caulk/mineral spirits is to help adhesion by forming a thin/weak coating. I have used 50:1 to touch-up my tarp several times over it’s lifetime. (The damage was usually caused by stretching around a pole or loop.) It will also add a small measure of UV resistance to the nylon. (Note that it does not stick real well to poly fabrics, but thin coats work pretty well.) Before the thin coatings, several people would use thick 5:1 coatings and have those coatings peel off on silnylon and/or poly.
More on the 5:1 ratio, Elliott, I would dilute it to 10:1/15:1 and coat raw fabric(both sides) with it to make it waterproof. This is followed by a second coat of about 15:1-20:1 several days later on the outside. This was done to create a rain jacket after all the tape/seams/vinyl coating had been damaged (from about 20 years of use.) The vinyl did not seem to cause any problems on the outside, nylon layer, but the vinyl did not stick inside. The first time I used it, it flaked, rolled off, off leaving little flakes all over my shirt. This is peeling. It didn’t leak, though. I destroyed it(ripped and shredded) a couple years ago bushwhacking across some rather dense forest about 3 years later. Apparently it was heavily UV damaged, since I could just tear the fabric with my hands using a light pull. None of my tarps do this, soo, I assume it was UV.
.
