Like marble or granite, slate is a natural stone product found in floors, counters and walls of homes to add a rustic and sophisticated look to the decor. Because natural stone is porous, it often attracts stains, and so most manufacturers recommend that you seal the slate in your home with stone sealant. If applied in the wrong place or at the wrong time, the sealant can discolour the slate and ruin the desired look. There are a number of steps you can take to remove accidentally applied sealer from slate.
Ventilate your work area by opening windows or running exhaust fans. You will use chemicals to remove the sealer from the slate, and these chemicals can produce strong fumes.
Pour more sealant over the incorrect area, allow it to set for one to two minutes and then blot up the excess sealer with cloths or towels. Adding more sealer to the surface will draw out some of the sealer already in place and will either lighten or remove the sealant from the slate. Repeat this as often as needed until the sealer is removed or the method stops working.
Clean the slate surface with a sealant stripper, available from natural stone speciality retailers. Be sure to follow all instructions on this product carefully, as some such products are caustic and can damage the stone or your skin if applied incorrectly. The stripper will break the bond between the sealant and the slate surface.
Repeat application of sealant stripper as necessary until the sealant is removed. Wash the slate in a stone cleaner to remove residual stripper, which will interfere with future sealing or cleaning if allowed to stay on the surface. Follow specific product instructions regarding application.
Make sure that the products you use to clean the slate are approved for use on slate. Slate is a relatively soft stone compared to marble or granite, so products designed for those harder stones could damage a slate surface.
Never use an acid-based cleaner on slate, as it will eat away at the slate surface.