When is pre-sealing required? For this article I have classed marbles, limestones and travertines as a marble. The pre-sealing of honed, semi-honed, extremely porous, textured and antiqued marble with Lithofin MN Stain-Stop or Lithofin Stain-Stop >W< prevents the penetration of the moisture from grout during the grouting process. The sealer prevents the grout from absorbing into the tiles pours so it can be wiped from the surface during the grouting process and prior to the grout drying. If the tiles are not pre-sealed the grout will absorb into the open pores and also cure on the surface where it cannot be removed without the use of an acidic cleaner or a mechanical process. Once the grout has dried, the tile should already be clean and only require a wipe down with a dry towel before re-sealing. Re-sealing a tile after grouting is required to ensure the tile is sealed correctly and to seal the grout lines. Polished marbles are denser because the polishing process reduces the stones porosity and therefore the grout residues are easily wiped from the surface during the grouting process. Even on polished marble grout residues cannot be allowed to dry on the surface and must be removed during the grouting process. As granite is a hard stone and resistant to acid we can clean the tile with Lithofin MN Builders-Clean to remove grout residues and builders dirt after grouting. Bluestone and basalt with a polished or honed finish must be pre-sealed prior to grouting with Lithofin Stainstop >W< as their surface can be altered by acidic cleaners. Testing these materials’ resistance to acid etching is recommended. To successfully remove grout residues from a natural stone tile an acidic cleaner like Lithofin MN Builder-Clean must be used. No other cleaner is going to clean it better than an acid based cleaner, however, as we know we cannot use acidic cleaners on marble as it will acid etch the surface. See our acid etching blog here. Hint - applying a little Lithofin MN Easy-Care in the washing water during grouting helps clean up the grout residues. Pre-selaing porcelain and ceramic tiles is not required as these materials can be cleaned with Lithofin FZ Cement-Residue-Remover after grouting to remove grout residues and builders dirt to prepare the tile for sealing or use. Hint - Add a splash of Lithofin FZ Cement-Residue-Remover into the washing water during the grouting helps clean up the grout residues. Confirm your requirements with your tile supplier or tiler. Happy tiling.