Discolored or stained grout on a slate floor can make the entire area look dirty. Because of this, cleaning the grout is necessary. When you are dealing with a slate floor, using most traditional floor care chemicals isn't recommended because these products may damage the floor. However, it is possible to clean the grout using cleaning agents that won't irreversibly damage the slate floor.

1
Keep the slate and grout clean by mopping the floor with a damp mop at least every other day. A wet mop may cause streaking.

2
Blot up spills as soon as they occur using a clean towel. Food and drinks may cause discoloration in the grout.

3
Wipe the grout with a towel dampened with one part plain dish detergent and four parts water. Don't use any detergent that has bleach or bleach alternatives.

4
Scrub the grout using a toothbrush if there are stains or spots that won't come off with the towel. Use one part dish detergent, one part baking soda and four parts water to dampen the toothbrush.

5
Dry the grout immediately after you clean it. Allowing water to set on the grout may cause cracks and chips.

6
Apply an acid wash to the tile and grout if there are still stains and discoloration. Acid washes for slate flooring are available at most tile stores and home improvement centers. Follow the manufacturer's directions for the acid wash.

7
Hire a professional to resurface the floor and repair grout if the floor is in really bad shape or if your previous efforts to clean the grout have failed.