What are some good tile grout sealers?

The North American Tile Cleaning Organization recommends the Stonetech Bulletproof Sealer and the Drytreat Stainproof Sealer as tile grout sealers. The difference between the two, according to their comprehensive evaluation, is in price and the volume of volatile organic compounds found in the sealer.

The Stonetech product, a significantly cheaper low-VOC compound, is useful only in ceramic and porcelain tile applications; in contrast, Drytreat is a high-VOC substance, useful to seal dense stone tile grout. The volatile organic compounds are a toxic byproduct of the sealer manufacturing process; it is recommended to use the lowest VOC sealer necessary to seal the grout material effectively.