A scratched floor tile doesn't necessarily require hunting down replacement tile, which can be difficult if you didn't install the slate in the first place or the product is no longer being made. While spot fixes like mineral oil can diminish the appearance of scratches, they can also affect the color of the tile around the scratch and aren't a permanent solution. The best way to repair scratched slate is to re-seal the entire floor. This ensures color continuity with the other tiles and helps prevent future scratches.
Step 1 - Protect your Work Area
If possible, remove furniture and appliances from your floor before starting. Use the wide masking tape along the bottom edge of any cabinets, walls, or appliances like refrigerators and dishwashers. This is to prevent getting sealant on anything but the slate.
Step 2 - Clean your Surface
Wipe your tile floor clean with sponge or rag and an approved stone cleaner. Avoid chemical cleaners such as those used for vinyl floors or showers, as these are often too harsh for stone and can damage your floor. Stone cleaners can be found at your local home improvement store or at stores that specialize in tile and stone. Vacuum away any dirt and loose debris, preferably with a hand held vacuum or a vacuum hose attachment, as regular vacuums can actually cause more scratches. Inspect the floor closely to make sure it is thoroughly clean.
Step 3 - Apply your Sealant
For this project, you will want a penetrating sealant, not a surface sealant, to provide the most protection for your slate tiles. It's best to choose a sealant specifically formulated for slate floors. If your scratches are drastically lighter than the tiles, you may want to choose a color-enhancing sealer that matches the color of your floor. This will darken the scratched area and keep the rest of the floor consistent in color.
Read all of the instructions and safety precautions on your sealant before you apply. Starting in one corner, use a paint roller or paintbrush to apply a liberal, even coat of sealant, working backwards over the entire floor. Let the sealant penetrate the stone for at least 20 minutes. If you know your slate is particularly porous, wait 30 minutes after the initial application has penetrated and apply another coat of sealant.
Step 4 - Smooth Things Over
Wait 30 minutes to allow your final coat of sealant to penetrate. Then dampen a clean towel with additional sealant and gently wipe the surface of each tile with the towel. This removes any excess or residual sealant, ensuring the sealant has been absorbed evenly across the tile.
Step 5 - Step Away
The sealed floor will need between 24 hours to 72 hours to cure completely. It should not be walked on for eight hours after sealing. Slate floors should be re-sealed every few years, as recommended by the sealant manufacturer. It is best to stick with the same sealant when re-sealing; different products can react badly to each other and damage your tiles.