We thought that our grout was dirty, but what we found out was that our entire floor needed to be honed, not just cleaned. Adam took the time to explain the process and what we could expect.  The process took several days.  They have the best equipment for this type of job.  It is a wet and messy process, but they do an excellent job keeping the area outside of the area they are honing as dry and clean as possible. The transformation is remarkable and well worth the expense and time.  I highly recommend Bio Tile.