After cleaning:
Not cleaned yet:
Then I tried it on this table -- I had forgotten that the grout was actually white to start with:
Here is what it looked like couple years ago (after about 8 years use):
FORMULA
7 cups water
1/2 cup baking soda
1/3 cup lemon juice
1/4 c vinegar (I used white)
Shake it up in a spray bottle. Spray on grout, wait a couple minutes and scrub. This is so easy. No hard scrubbing -- just brush lightly with a scrub brush. I found that it does leave a residue so tile should be wiped with a wet cloth after cleaning grout.
I always want things to do multiple duty so I tried it on the black spots on the rubbery caulk in the shower but it didn't do the trick. Just lightened it a bit. Maybe repeated use would eventually fade it. I also tried it on a small section of vinyl floor. Again had the residue issue but it might have possibilities for older vinyl that has dirt embedded in the texture. For grout it's amazing.