I love it when I find a product that actually works. Last weekend I tried Meguiar’s Canvas Cleaner to spruce up the white zippers on my canvas. There was a small leak in the winter cover and the water ran along the zipper turning it a lovely shade of slime green. I sprayed on the Meguiar’s and let it soak for 30 seconds then wiped with a clean cloth (you can also rinse it with water). It removes dirt, stains and mildew. It is safe for the environment and biodegradable. I have included a picture of the before and after. I found it at West Marine for $15.