This product is not effective for removing Water Spot Etches, which occur when hard water spots remain on an unprotected surface for a prolonged period, causing minerals in the water to corrode the surface.
A water spot etch looks just like a water spot. Hard water can etch all surface types including paint, glass, gel coat, and stainless steel. (Glass is the most susceptible). In most cases water spot etches cannot be removed and refinishing or replacing is the only option.