This is one of the most common questions we are asked about Travertine Tiles. We recommend that all natural stone is sealed using an appropriate impregnator. We sell and recommend the Stonefix range of products that are specifically made for natural stone installation and maintenance. See Stonefix Impregnator. You should never use bleach on any natural stone, especially Marble Tiles and Limestone Tiles. Flash isn’t that great either. The best cleaner to use is a specially formulated natural stone tile cleaner. You can get this from us or buy locally from your local hardware superstore.