Slate is a hard stone that when used for tiling creates a durable, long-lasting surface. Slate is also a porous tile and stains easily because it absorbs moisture beneath its surface. This easily stained nature means that you have to finish slate tile carefully whenever you use it to tile a surface. Fortunately finishing slate tile is not a difficult process, it just requires that you place the tiles keeping the nature of the material in mind when dealing with anything that may affect the tile surface. After placing the tiles in the mortar, you can begin the finishing process that should leave your tiles stain-free for a lifetime.
Lay your slate tiles in a bed of mortar to secure them in place. Allow the tiles to sit overnight for the mortar to set before beginning the finishing process.
Seal the surface of the tiles prior to apply grout to the joints between the placed tiles. Applying grout to unsealed slate tiles will discolour the surface of the slate, leaving it darkened and blotchy. Grout placed on unsealed slate tiles is also difficult to remove because it seeps into the pores of the tile’s surface. Pour the sealant into a painter’s tray and then spread the sealant over the surface of the tiles with a paint roller, following the grain of the slate. Allow the sealant to dry overnight before continuing.
Grout the joints between the sealed tiles. Fill the joints by placing the grout directly onto the surface of the tiles. Spread the grout over the tile surface with a grout float pushing the grout into the joints between the tiles.
Wipe excess grout from the tile surface within 15 minutes of application using a damp sponge. Wait 30 minutes for the grout to begin to set and then wipe the surface of the tiles with a clean lint-free cloth to prevent grout residue from developing into a haze on the tile surfaces.
Cover the tiles with rosin paper to protect the surface as the grout sets. Tape the rosin to the surrounding surfaces, and not to the tiles. Wait 30 days more for the grout in the joints to harden completely.
Remove the protective paper, and then seal the tiles and grout with the slate sealant. Wait two hours for the sealant to dry and then apply a final coating, allowing the last coat of sealant four hours drying time before using the surface.