YES natural stone is porous and will stain unless it is properly sealed
Aside from staining, not sealing any natural stone tile can lead to mold and mildew growth, and the porous surface will...
It depends on the type of tile you have. If the tile is unglazed and porous (as mostly all travertine is) then you will need to seal the tile before you grout it so that the grout does not soak into...
A product called enrich and seal. my husband is a tile contractor and that is what he uses. We also used it in our own home. Once a year is sufficient.
In Cabo Mexico I get $1.05 usd a sqft. It ranges from .85 to $110 usd
Gert de Herrera
Hogares Distintivos de Los Cabos S de RL de CV
Distinctive Homes of Los Cabos
Real Estate Sales, Marketing...