Impregnator/Penetrating Sealer is either solvent based or water based and commonly contains silicone, flour-silicate or other silicon derivatives. It is designed to penetrate below the surface of the stone in order to occupy its pores and prevent water, dirt, and other material from entering the stone. Meanwhile, still allowing the moisture underneath of the stone to evaporate through the stone.
Most impregnators will not change the appearance of the stone and they will not make the stone more slippery. However, some impregnators are designed to enhance the color of the stone giving it a “wet” look. In some cases, the impregnator will damage the resin applied by the factory in order to give the stone a better look. Unfortunately, this can cause an uneven shade of the stones appearance. Therefore, a sample test must be conducted before applying the impregnator.
You might ask, “Does every stone need to be sealed?” Well, that depends on the individual stone you are working with. Some stones are very porous and have extremely high absorption ability. In this case, you are dealing with stones that are easily stained. These stones need a very good penetrating sealer. Other stones, which have very low absorption ability, might not need any sealer at all. In order to know if a stones absorbency high or low, we can simply perform a test with a drop of water. Firstly, drop a drop of water onto the stone, and wait to see how long it takes for the water to darken your stone and penetrate into it. If it the water only takes a few seconds or less than three to four minutes to penetrate the stone, then the stone should be sealed. On the other hand, if the water takes more than four minutes to penetrate, the stone is considered slightly porous and may not need an impregnator.
An impregnator sealed stone is not 100% waterproof and/or chemical resistant. Therefore, the word “seal” itself confuses most people. A well-sealed stone is water repellant or oil repellant, but not waterproof. Due to this fact, it is not recommended to use an impregnator/penetrating sealer on swimming pools or bathtubs, which would be subjected to a high pressure of water. Also, at this time, there are no impregnators on the market that can protect stones from acid etching.
Never apply impregnators on wet stones or on the stones with efflorescence occurring.