How Do You Seal Slate Tile & Grout?
Slate tile is a natural stone product, which means it’s more porous and absorbent than clay-based products like ceramic. Unsealed slate will absorb grout and could end up permanently stained from it, which means you have to seal the tiles before grouting. However, if sealant gathers in the grout lines, the grout may not set properly. The solution is a careful two-step sealing process that starts after you install the tiles but before you grout. Start with fully set tiles with about 1/8 inch of space between them. Run a wood shim along each joint between the slate tiles to loosen any residual mortar or other obstructions. Use a vacuum hose to vacuum out the lines. Brush tile sealer onto the surface of the slate, using a paintbrush. Make it a thin, even layer, with the brush strokes all going in the same direction. Seal only the face of the slate tiles, not the sides. Avoid getting the sealant in the spaces between the tiles. Allow the sealer to dry for two to three hours. Apply a second
