Why is canvas tearing?

[Treewater]

I used the only product I could find at hardware stores. Lowes carried this "MoldControl, concrobium" at $32 for a gallon. Says it had no bleach or amonia. "eliminates, prevents, kills." it was advertized as good for lumber or cloth. There were several mold cleaners on the market but they contained bleach or amonia, or acids. This is water based and while the consistency of water, I still used a brush to put it on. I had to brush hard to get it to penetrate but eventually it soaked the canvas and as I said, it also shrank the canvas enough to pull the small ripples out.
Zinc napthanate was unknown to all I spoke with and of course, no one carried it.

 

[Andre Cloutier]

I used the only product I could find at hardware stores. Lowes carried this "MoldControl, concrobium" at $32 for a gallon. Says it had no bleach or amonia. "eliminates, prevents, kills." it was advertized as good for lumber or cloth. There were several mold cleaners on the market but they contained bleach or amonia, or acids. This is water based and while the consistency of water, I still used a brush to put it on. I had to brush hard to get it to penetrate but eventually it soaked the canvas and as I said, it also shrank the canvas enough to pull the small ripples out.
Zinc napthanate was unknown to all I spoke with and of course, no one carried it.

Concrobium came out as widely available in the marketplace some years ago up here, it was previously used by contractors as a mold abatement product, and is really the only thing in the marketplace that truly works. It is prohibitively expensive up here, and typically is sold in smaller spray bottles. Never thought of using it, but glad it worked for you. Wetting the canvas even with water would have tightened it, just a happy byproduct of treating it after its stretched on the boat.

 

[Lazy Jack]

I looked up the MSDS for Concrobium 'Eco-Wash' product - a proprietary mixture of purified water, food grade inorganic salts, and natural surfactants/detergents - no indication of what the salts are (the proprietary part presumably) but they are highly water soluble and according to the MSDS, non-toxic.

Being so water soluble, I imagine any protection this stuff offers the canvas is pretty rapidly washed away as the canoe is used.

 

[Treewater]

Being so water soluble, I imagine any protection this stuff offers the canvas is pretty rapidly washed away as the canoe is used.[/QUOTE]

Good point. So if I apply the filler on the outside that should seal those "salts" in. If I take a step I never intended, varishing the inside, then that would seal the salts from the inside since each gap in the cedar plankning will allow paint inside to the canvas. Obviously, a very thin varnish would be desireable.