Try this in your kitchen. Wet a white paper towel, wring it out, and rub it hard along a grout line for ten seconds. If it comes up brown, the dark color in your grout is dirt sitting in the pores, and it will come out. If the towel stays clean and the grout still looks dark, it's stained deeper, and a cleaning will lighten it without getting it back to new.
Most of the floors we see around Dentsville are the first kind.
Why grout gets dark in the first place
Grout is porous, a bit like a dense sponge set in cement. Every time you mop, dirty water runs off the smooth tile and settles in the lines, a bit lower than the tile itself. The water dries. The dirt stays. Do that a few hundred times and a light gray grout turns the color of wet sand. Kitchen grease adds to it. So does the sandy grit tracked in from the yard, and in a bathroom you get mildew on top.
A mop can't fix it because a mop is how it got that way.
What we do differently
Look first
Your technician checks the floor and works out what it is. Ceramic and porcelain are the common ones around here; travertine and other natural stone turn up in some kitchens and baths. Soft stone gets a softer setup and a test in a corner. We also point out cracked grout and any etching that's already on the stone, so nobody blames the cleaning for it later.
Pre-treat
A non-toxic pre-treatment goes down and sits long enough to soften whatever's caked into the tile pores and grout lines.
Run the buffer
Here's the part that matters. A machine buffer scrubs the face of the tile and works its bristles down into the grout lines, lifting out the buildup that's been sitting there for years. It does in an hour what a kneeling person with a toothbrush can't do in a weekend. The brush or pad changes with the surface, firmer on porcelain and gentler on stone.
Hit the hard spots
Stubborn grout stains, mildew in the shower, and grease near the stove get extra passes. Shower walls, tub surrounds, and backsplashes get the same treatment as floors.
Rinsing and drying the floor
A final rinse takes the loosened soil and leftover product off the floor. Very little water is used, so the floor dries quickly with no slick film. Give it a few hours before the dog goes skidding across it.
Rooms we clean
Kitchens and baths are most of it. Showers too. After that come entry halls, dining rooms, the odd tiled living room, mudrooms and laundry rooms. Tiled garage floors and covered patios are fine as well.
What we never use
Bleach and acid. They're fast, and they're hard on grout, slowly eating it away, and an acid can etch marble or travertine in seconds. You'll find both in plenty of store-bought grout cleaners. Our approach relies on the pre-treatment and the mechanical scrubbing of the buffer.
How often
For most homes, every 12 to 18 months keeps grout looking light. A busy kitchen, a mudroom by the back door, or a house with big dogs may want it once a year. In between, mop with plain warm water or a pH-neutral cleaner, change the water often, and don't let it puddle in the lines.
If you like to read up before a job, our sister site has a longer write-up on why grout darkens and how buffer cleaning pulls it back out, stone floors included.
The $45 tile coupon
It's on the coupons page. Tile gets priced by area and condition, so the real number comes once the technician has seen the floor, and the buffer doesn't start until you say go. A rough square footage and a list of rooms helps when you call 803-310-3848 or write through the contact page. Not happy afterward? Then it's free.