1. Pre wet with water.
2. Apply a High Alkaline cleaner diluted 4:1.
3. Allow to dwell 15 minutes.
4. Whip over it with a mono rotary fitted with a soft to medium brush.
5. Then rinse and vacuum up.
Then offer to seal if you want to. A lot less mess to clean up than PW and no damage
Kev Martin
Marblelife ltd