Here’s a really complete article on ceramic floors and grouts.
Among other things it discusses the permeability ratings for the ceramic floor itself and the process of glazing.
More to the point, grout can be the bane of our existence, and they recommend a couple of restorative interim maintenance procedures (pressure washing and rotary brush cleaning specifically).
The “aha moment” for me was that while we tend of wait till the grout shows dirt, instead putting a grouted ceramic floor on an interim scrubbing program (as we would do with carpet or finished vinyl tile) would prevent or limit the soiling we so often see.
I do take exception to their statement that micro fiber is inferior to string mops in that it accelerates the darkening of grouted floors.
First, the statement that it leaves more chemical on the floor to settle into the lowest points – the grout lines – isn’t true in our experience.
With proper dilution and proper wetting microfiber leaves less not more fluid on the floors. Further, the proper dilution for microfiber uses significantly less detergent that the proper dilution for string mops, so even with comparable amounts of residual mopping fluid there should be less detergent deposited.
Finally, since much of the soil actually adheres to the microfibers rather than being suspended in the mopping fluid, any minimal remaining fluid should contain less dirt with microfiber mops.