Does this work on stubborn patio umbrella mildew and stains; if so, at what concentration?

Start with 10:1 — go big at 5:1 if it’s super stubborn. Use it with an abrasive of some sort; one that is not colored so as not rub off on the umbrella. When you get stain and mildew on canvas that’s cooked in the sun for a long time, it can be a beast to remove. The struggle is real!

Happy Cleaning!