The picture that most people have in their mind about a sealer and it’s expected performance is of some sort of “cocoon” that envelops the Stone and turns it into a Bulletproof material. For starters, impregnating sealers are two-part products: one is the carrier, which could be mineral solvent or just plain water while the other part is the solid that will be left behind when the carrier evaporates. The most popular sealer particals are silicone, silane, ester epoxy, fluorocarbon aliphatic (a.k.a. fluoro-chemicals).
Second and very important, is the fact that sealers for stone are not topical products like any other sealer people are familiar with. In fact, they are below-the-surface sealers. The first implication of this is the fact that a sealer for stone will not offer any protection to the surface of the stone itself from wear and tear or chemical attacks. The second implication is the fact that a sealer for stone will not alter the original finish on the stone surface produced by the factory or somehow structurally reinforce the surfaces.
The most important phase of the application of a sealer for stone is to make sure that all residue of the product is thoroughly removed from the surface of the stone before it has a chance to dry. This means that at the end of the application of the sealer, the surface of the stone will be as bare as it was before the sealer was applied to it that being said, let’s now elaborate the principle of a below-the-surface sealer. The product goes inside the stone; the carrier (water or mineral solvent) evaporates, while the solid part (the resin) will remain inside to clog the pores of the stone to an average depth of approximately 1mm. (The more porous the stone is, the deeper the impregnator will go.)
Now how does an impregnating sealer go inside the stone? Quite simply, by being absorbed into it: the product is applied on the surface of the stone, which in turn will absorb it. Now that we know what sealers do it’s important to know that not all stone is created equal. Some stones are so dense that sealant simply cannot break the surfaces tension and will not absorb into the stone. (Blue Pearl, Uba Tuba ECT…) others are so porous that multiple applications of sealer are required to properly seal the surfaces. (Ambrosia White, St Cecilia, Giallo Ornimental ECT…) For the best possible results sealer needs to dry between coats restricting applications to once a day in an environmentally controlled environment.