Slate is a metamorphic stone made from sedimentary deposits along river beds. There are many different types of slate. Most installed slate tiles are porous in nature and have a somewhat chalky appearance. For these reasons many people choose to seal their slate tiles with a topical glossy sealer.
Glossy sealers look beautiful and also protect the porous slate from spills, dirt and contaminates. Most topical sealers for slate are water based wax sealers. While these sealers look beautiful and bring out the natural beauty of slate they do have a limited lifespan. While the sealer will continue to protect the slate, over time it will get scratches and scuffs making the sealer look dull and loose its beautiful glossy appearance. To restore the slate tiles back to their beautiful appearance the wax sealer must be stripped from the slate surface.
To remove the wax sealer you need a water base floor stripper. Water based floor strippers can be found at most janitorial supply stores. Additionally the big box stores carry water based floor strippers but generally they are not as effective as professional strippers from janitorial supply stores. Mix the stripper with water in the strongest ratio recommended on the manufactures label. As with most harmful chemicals wear rubber gloves and also a rain suit to keep the floor stripper off of your skin. Generally water based floor strippers do not have very strong fumes but you may want to consider wearing a respirator if you are sensitive to chemical odors.
Apply the stripper to the slate tiles with a scrub pad or mop and let it dwell on the tiles and grout. Do not let the stripper dry on the surface. Let it dwell there for as long as it takes to emulsify the sealer from the tiles and grout. While you are letting the floor stripper dwell on the tile and grout you can begin to scrub the sealer coating with an aggressive scrub pad. Do not use any type of steel wool or metal pad that can scratch the tile surface. Always test the surface you are about to scrub to be sure your scrub pad will not make any permanent scratches on your slate tile surface.
You will most likely notice that the sealer can be removed from the tile surface with minimal scrubbing but the grout will require some extra scrubbing to emulsify the sealer. Keep scrubbing until the sealer is completely emulsified from the grout lines. After you have emulsified all the sealer from the tiles and grout remove the emulsified sealer and excess floor stripper from the tile and grout with a shop vac. Then use a mop and water to remove all the excess stripper from the tiles and grout. After you have completed this process you may notice that there is still some sealer left on the slate tiles and especially the grout. It may be necessary to repeat the process until all the excess wax sealer is removed.