It's one of those things that happens gradually and then suddenly. You had nice, clean grout, and now, as time goes on, darkness is creeping along the edges of your tile and your bathroom looks like it's auditioning for Swamp Thing.
What to do?
Mildew and mold, both non-edible types of fungi, tend to colonize on moist, warm surfaces. They love a good humid hangout any day of the week.
Although the sustainable person in us would love it if vinegar did the trick, this is often not the case. For a full-on, ground zero assault, you need bleach. Copious amounts of bleach.
Oxygen bleach, chlorine bleach, or even hydrogen peroxide will kill the fungal spores and eliminate the greenish brown or black stains mold leaves behind.
Our favorite product is Clorox Toilet Bowl Cleaner Clinging Bleach Gel.
Squeeze the clinging bleach gel (it's named "clinging" because it actually does) in the grooves of the grout and let sit for at least 30 minutes. Then take a toothbrush or scrub brush and assault with fervent, purposefully targeted elbow grease. The mold should lift up and bleach the grout white.
Paige Blu Industries is a commercial cleaning company headquartered in Los Angeles.