Why a mopped floor still looks dirty
Glazed ceramic and porcelain are effectively non-porous. Very little sticks to them and a damp cloth removes almost anything. The dirty appearance of a tiled floor comes from somewhere else.
It comes from the three or four millimeters of grout between every piece. Cement-based grout is porous with a rough surface, and it sits slightly below the tile so that everything drains into it: coffee, cooking grease, mud from boots, and above all the water from the mop.
Mopping is not neutral here. The mop lifts soil off the tile, suspends it in the bucket water, and then spreads that water across the floor, where it settles into the lowest point, the joint. Repeat that weekly for five years and every grout line holds a concentrated version of everything that has been on the floor.
What the clean does
Heat and pressure are applied into the joint to break the bond between the soil and the cement, and the released soil is extracted immediately so it is captured rather than running into the next joint along. A brush and a bucket cannot do the second half: brushing lifts the dirt out of the pores and the rinse water carries it two tiles over and drops it again.
Corners, edges and the line where the tile meets a cabinet kick-plate are cleaned by hand, because the machine head cannot sit flat there and that is usually where the darkest grout in the room is.
Soiled grout and stained grout
The difference is worth understanding before you decide whether the work is worth doing.
Soiled grout is clean cement with dirt in its pores. It comes back a long way, and the result surprises people who had stopped noticing how dark the floor had become.
Stained grout is cement whose color has been changed: rust from a metal table leg, red wine that sat overnight, dye from a cheap mat that got wet. The pigment is in the material now. Cleaning removes everything around it and the stain remains.
Most floors are largely soiled with a few stained patches. We point out the patches before the work begins.
The bathroom
Bathroom grout darkens for a different reason: soap scum, body oil and mold in a room that stays humid. It cleans well, and one distinction is worth knowing. Surface mold on grout comes off. Discoloration that returns in the same spot, particularly low on a shower wall or along the base of a tub, can mean water is getting behind the tile. That is a repair, and cleaning it every few months treats the symptom only.
If we see it, we tell you.
