When cleaning sandstone, dry it using a towel or a clean mop instead of letting the surface dry naturally. Also, vacuum the surface before cleaning to get rid of loose grit and dust. High quality microfiber cloth can eliminate the need to use cleaning detergents and chemicals in most cases.
Since sandstone is both porous and soft, it can absorb large quantities of stain-causing liquids. Even water often results in staining when it is left to seep into sandstone. The best way to clean sandstone that is not heavily stained or contaminated is using a circular motion with a damp cloth, much like waxing a car. After the surface is clean, wipe off the water and apply a preventative sealing coat to keep the sandstone in good shape.
When dealing with heavy stains, commercial sandstone cleaning paste offers the best results. If using a commercial cleaning paste or detergent, let it sit on the sandstone for 50 minutes before wiping it off. If the stain rubs off onto to the cleaning towel, leaving a dark smudge on the fabric, it means that the cleaning is successful. After wiping the sandstone clean, spray it lightly with water and wipe it dry with a clean towel.