Penetrating Sealers are water based sealers that use siliconates, fluoro-polymers and siloxanes that repel liquids.
These sealer actually form a permanent chemical bond with the stone surface by penetrating the surface of the stone enough to anchor the material to the surface. This means they last for many many years without much of maintenance.
Penetrating Sealers are also called as densifiers as they fill the pores on concrete thus making it denser. This increased density blocks out moisture and other damaging chemicals/agents like salt, oil, grease, etc. Penetrating Sealer are great for protecting the concrete from physical damage like frosting-defrosting, salt, cracking and other damages.
In Comparison with Topical Sealer
Penetrating Sealer last longer than topical sealers and also do not majorly alter the appearance of the stone. But I can still change the slip characteristic of the surface and wear off quickly.
Penetrating sealers are usually clear, but you also have tinted sealer available with only few brands. These sealers are breathable to certain degree but do not penetrate deep enough (less than 1 mm) to be effective against salt attack such as efflorescence and spilling.
Penetrating Sealers usually require use of special cleaners that cleans and also tops up the repellent ingredient left on the stone surface.
Penetrating sealer cost around Rs.30 – Rs.35 per square feet. Unlike Topical Sealer, penetrating sealer can be used for both dado i.e. external use and for floorings too.