For coating or recoating silnylon, there are as many "formulas" out there as people it seems. These are some that I have used (over ten years of recoating tarps, tents and ground cloths.)
1) For recoatoing silnylon: 20:1 or if it is badly streatched 30:1 both sides.
2) For recoating silnylon floors: 15 or 20 to 1, both sides
3) For coating a small piece of untreated ground cloth: 15:1, both sides.
4) For sealing seams, a 5:1 mix applied with a small brush or syringe works pretty well.
After drying a light dusting of talc (unscented baby powder, NOT corn starch) will remove stickiness. It takes about 24-48 hours to completely dry. The mineral spirits evaporate and the curing of the calk both happen at different rates.
The peeling happens when the coating becomes stronger than the fabric/sealer bond. That is, the calk sticks to itself stronger than it sticks to the fabric. Generally, washing silnylon is not recomended but if you plan on recoating it, it helps with adhesion. Two coats will also bond through any breaks in the origonal coating to increase the actual bond on the fabric if it is applied within about an hour or so.
On silnylon, thicker is NOT better. Thicker coating will peel far faster than thin coatings. Two very thin coatings (40:1 or 50:1) will often revamp an older tarp that is wettin through, but not leaking. Light coatings often repel UV much better. White silicone calk has tungston oxide in it which stops UV. So coating a .2oz coating over a white tarp will extend the life expectancy by about double. UV damage will often manifest itself as weaker portions of fabric: pulled loops or growmets, small splits. Note that while not technically an adhesive, it will bond fibers togetehr making a fly or tarp somewhat stronger, sort-of repairing a UV damaged tarp for a year or two.
