All natural stone tiles are porous, meaning they can absorb grout, dirt, spills and debris, causing them to discolour over time. To prevent this from happening, a sealant should be applied to the stone before the tiles are grouted, and repeated as needed.
Different stones have different needs. Soft stones like limestone and travertine need a heavy-duty sealer, while granite or marble can use a lighter sealer. Slate tiles and tumbled marble tiles may also benefit from a sealer that a has a colour enhancing agent in it to deepen the colour of the stone.
Pour the liquid sealant from the container into a dish or tray wide enough for you to dip in a foam paintbrush or foam roller. Dip the brush or roller and fully saturate it with sealer.
Brush or roll the sealer onto the stone tiles starting at the back or top of the installation and working down. The sealant will go on wet, allowing you to see the amount of coverage and avoid leaving uncovered spots. Allow the sealer to sit on the stone for at least 10 minutes, but no longer than 20, as it will begin to dry out.
Use an absorbent cloth to buff the stone dry, removing any sealer that has not been absorbed into the pores of the stone. Keep rubbing until the tiles are completely dry to the touch, with no sticky or slick residue left, before grouting, walking on or using the tiles.
Well-sealed stone will bead water up off of its surface like a waxed car. When your stone ceases to bead the water placed on it, it is time to reseal. The time frame for this will vary by stone, use and application.