Wipe down your marble tile. Get rid of all surface dirt and crumbs that might make cleaning your grout more tedious by wiping down your trend rustic tile before getting to the grout cleaning. Follow your regular cleaning regimen by sweeping and mopping floors or using a spray cleaner to wipe down countertops.
Create your solution. Oxygen bleach is a safe bleach compound, which works to dissolve bacteria and grime while whitening grout. Mix equal parts of oxygen bleach with warm water and allow the mixture to dissolve.
Apply your cleaner. Choose your starting area, no larger than 1-2 square feet at a time, and pour on your bleach. Make sure the grout is thoroughly coated with the liquid; you can use a spray bottle if it makes it easier to do so. Leave the solution to work on the grout for 15-20 minutes.
Begin scrubbing. When the bleach has had time to set, you can begin scrubbing at the grout to work out the dirt and stains. Use a small brush, like a toothbrush, to rub the grout. You can add more bleach as you scrub to keep the area moist and expedite the cleaning process.
Mop up the excess liquid. Grab a dry towel and mop up the dirty bleach-water that pools on the tile when you finish scrubbing. If you get enough, wring the towel out between uses. Doing this, will make it easier to finish cleaning in the end.
Continue washing your grout. Repeat the process of applying bleach to the grout and scrubbing it out until you have finished all your kitchen tile area. For particularly tough stains in the grout, you can apply the bleach for an hour or longer. The longer you let it soak, the easier it will be to scrub out the stain. Finish cleaning your tile. Do a final mop-up of your bathroom tile before cleaning it again as you usually would. A final wipe-down will remove any remaining bleach and dirt, and leave your grout shiny and good-as-new.