Slate is a naturally cleft, rustic stone tile with a lot of variation and texture. This can be beneficial to the moist environment of a bathroom, since the stone is less likely to be slippery. Unfortunately, the many clefts and ridges in a slate tile make it difficult to keep clean, since soap and hard water can build up on it easily. To help prevent stains, and keep the stone easy to clean, apply sealer to slate tiles in a bathroom.

1
Clean the slate tiles well. Use a stone cleaner and a scrub brush to remove any soap scum, mineral deposits or buildup from the stone. Pay close attention to the clefts, or raised areas, on the slate, since the edges of these areas may collect dirt. Rinse the slate with water and allow it to dry completely.

2
Pour a silicone-based sealer into an open-mouthed bowl or container large enough for you to dip a brush into. Saturate a paintbrush in the sealer.

3
Apply the sealer to the slate tiles beginning at the top of any walls and working downward, and at the back wall of any floor tiles, and working out to the door. Thoroughly cover the slate with sealer, using the paintbrush to work the sealer into any crevices or clefts, and paying attention to edges. The slate will appear wet and dark in color where the sealer has been applied; check for dry-looking spots to ensure nothing is missed.

4
Let the sealer penetrate the slate for 10 minutes and use strong, lint-free cloths to buff the tiles dry. Pay attention to the clefts and ridges in the stone to ensure no excess sealer is left there to dry. Deep pockets of dried sealer will be tacky and will negatively effect the appearance of the stones, so work carefully to ensure no places are missed in the drying process.