Carolina Grout Seal offers complete tile and grout repair and restoration services for Raleigh-Cary and Durham-Chapel Hill metro areas. Our patented waterproof grout sealer penetrates the micro-spaces in your grout so mold and moisture never return! Does your shower tile look disgusting no matter what you do? That "black shower mold" that you cannot remove is really embedded dirt. When unsealed grout gets wet, it expands allowing dirt to penetrate the surface. The grout then dries and contracts (often over time), allowing the dirt to embed deeply in the grout pores.