Suggestions for cleaning grout

[blueman]

The grout on our mudroom tile floor has gotten real "dirty" looking over the years. The tile is a tumbled Carerra marble type.

I would like to clean it and then reseal (using Porous Plus).

Any suggestions on either a good commercial grout cleaner or a homebrew potion that will remove grime and dirt stains to bring back more of the original grout color?

Thanks

[Oren]

For a homebrew; formulate a wet paste with TSP, Trisodium phosphate. Apply the paste in a small area to test. Allow it to set, nearly dry and then clean with water.

Your tile is not the same as mine, but TSP is safe and has really cleaned up some tiles/ grout in the past.

[Norminn]

I've used a couple of different brands of terazzo cleaner/sealer/polish. They are three-step products and give good results. I believe it is the same product used for marble, but don't have any right now to check the label. A tile shop or HD should have something similar for marble. Most of my cleaners say "don't use on marble", o/w I would recommend Scrubbin Bubbles - great for cleaning the shower tile.