I can only endorse what others have said regarding the effectiveness of this amazing product. Our block paved drive had accumulated 25 years of grime and the reddish stones were an unattractive dark shade of grey. I searched for an alternative to messy and destructive pressure washing and found Monty. One bottle did approximately 24 square metres with ease and the result is truly outstanding. Our patio at the rear has never looked better, with almost all of the black spot eliminated and our stone tubs look like new. Monty is so easy to use and I would recommend the solution without hesitation.