What is a penetrating sealer and why are they all the rage of late? A penetrating sealer, usually a silicate, is a sealer that is able to penetrate into the concrete and chemically react while leaving the surface with a completely natural finish as if it had not been sealed. Penetrating sealers are usually densifiers that seep into the pores and capillary tracts of the concrete, reacting, forming additional calcium silicate hydrate, thus strengthening and hardening the concrete. By filling in all of the pores and veins, mold, mildew, efflorescence and radon are reduced and prevented.

Silicates are available in a few different types of carriers, most popular being sodium and lithium. Sodium silicates are an older technology that provide excellent results for sealing and hardening concrete. Lithium silicate on the other hand are excellent choices for polishing floors and warehouses. If you notice the floors the next time you visit a big box retailer, you will see the shiny, smooth polished floors that used a lithium silicate sealer.

The only downside to penetrating silicate sealers is their inability to waterproof concrete. Although many companies out there claim that their silicates will waterproof because they are penetrating sealers is a false claim. In order to guarantee water protection the sealer needs to be a blend of a silicate and siliconate. While the silicate penetrates and densifys the siliconate is also chemically reactive, reacting with the carbon dioxide in the air to form an invisible hydrophobic barrier that is unable to peel, flake or bubble still keeping the concrete looking natural.

Our Take: Excellent silicate densifiers include Ashford Formula and Diamond Hard and for waterproofing we recommend Lithi-Tek LS 9500.