Sealers are used on certain types of tiles, and many recommend using a penetrating sealant with slate. Many others insist it isn’t needed or desirable. A quick search on the Internet will have both opinions stated quite forcefully. Why is there such confusion about sealing slate?
The answer lies in the fact that slate is not manufactured. This means there will be variations in the stone based on the location of the quarry and the minerals in the slate. Slate tiles cut from some areas of the world, like China or India, tends to be softer and more porous, so sealers are often used to counteract the tendency to stain. Since grout usually will need to be sealed anyway, most people find this a non-issue. It’s just a matter of following the instructions and paying attention to the time that should be taken for drying and curing between steps.
Other areas produce slate that is harder and less porous. Vermont and Brazil will typically produce slate of this type. Proponents of the no-seal school point to these harder tiles and say, “See? It works fine without the added chemicals and mess,” and they are right. IF the slate is hard enough to hold up to the location where it will be installed, there’s no need to seal.
Even these harder slate tiles are sometimes sealed if a different look is desired. Sealants often deepen the color of the stone, as if it were wet. So the answer to the question of sealing a slate tile floor will depend on the type of slate, the desired look, and the homeowner’s preference. There is no single “right” answer for sealing slate, and that is why it can be confusing.
Fortunately, the confusion can be cleared by discussing your project with an expert who understands slate tile flooring. In Montreal, those experts can be found at the showrooms of Éco Dépôt Céramique.