porous grout cleaning 2

https://wiki-triod.win/index.php/Why_tile_and_grout_sealing_is_essential_for_long-lasting_floors

Cleaning porous grout is tricky because it soaks up everything, so blasting it with a pressure washer or scrubbing with a stiff brush and an alkaline cleaner usually works best, then rinsing thoroughly to pull out the deep grime without damaging the surface.