If you have a bathtub with a slip-resistant bottom that still looks dingy, grungy and downright grimy no matter what you use to clean it, I have really good news and at least one surefire solution that will even bring an older tub bottom back to being clean and like new!
Since the Americans with Disabilities Act became law in 1990, all bathroom flooring must be non-slip. Kohler porcelain tubs come with a patented Safeguard slip-resistant surface, which has a very distinctive look and seems to be the most prone to this ugly, dirty problem.