I love doing experiments. Here is what I found.In a recent experiment, I showed that canvas, when glued to foam the right way with TB2, holds almost as well as Glidden Gripper, and better than almost anything that is still on the market.
However, there was a persistent question about how waterproof canvas, soaked in TB2 mix, could be. So I took a small piece of canvas and soaked it in a 75/25 mix of TB2 and water. When I say soaked, I mean that I poured the mix on the canvas and rubbed it in with my hand until I made sure it was in every fiber. It absorbed a lot of mix. I then placed it over the end of a pipe to dry.
It dried into something that reminded me of the ash tray I made for my parents when I was in elementary school.
After the first coat dried, I put water in it and it leaked right away. I then applied a second coat of the mix and I made sure to rub it into the fabric like I did with the first coat. It also took a good amount of the mix, but not quite as much as the first coat. After it dried, it still leaked but slower. A third coat was applied and the canvas did not absorb much of the mix. After it dried, it didn't leak, but under the canvas felt moist. So I put on a fourth coat and the canvas barely absorbed any mix. When it dried I filled it with water. No leaks!
After a week
Still full of water and no leaking. No primer, no paint, just TB2 and water was used in this experiment.
Conclusion, if you're going to use TB2 mix to waterproof your canvas, keep applying it until it refuses to absorb any more mix. I'd say a minimum of 4 coats of the mix, preferably more, and that you work it into the fibers of the canvas. Primmer and 2 coats of good exterior paint on top of that should seal the deal.
As always, don't trust me, do your own experiments and find out for yourself how this works before you build.
