I've got another question. I just applied GAC 400 to stiffen a canvas and it seems to do a better job that Gamblins PVA Size. I love the tightness of the canvas just after putting on the GAC 400 and it's still wet. Beautiful drum sound. I followed your double coat instructions from the Web site. But after it dries, the tightness of the canvas diminishes by about 50%. Is there any way that I can keep that super wet tight tension permanently?
The tightness of a wetted canvas is something we have been trying to capture for some time now. Some people claim it can only be achieved by keying out the stretcher bars after the film dries, but I think if it can be achieved with Rabbitskin Glue, there has to be a way to do so with acrylic mediums. The trick of course is discovering how.

I think the GAC 400 is the closest product we have thus far, but it may be that it's too complete of a film to allow for the tightness to remain. I've only done limited testing with this, but I think if the GAC 400 is reduced at least 50% with water before applied it will shrink more before drying into a film and achieve a tighter canvas. I also think the environment has something to do with it, but I have not tried to control this yet. It may be a slower drying mixture will do better than a fast drying one, but who knows? It may be the opposite. However, I do think that the canvas needs to be completely saturated to keep it constant and offer less tension to the paint film. Only coating one side seems to "cup" the canvas over the years if the canvas is relaxed.