Black specks in grout

[diamond brian]

I have a question for you experts.

I do all of our tile and grout cleaning. Occasionally, light-colored grout won't clean up as well as I like. It's as though there are tiny black specks remaining in some of the grout lines. Enough of these specks and it'll still appear "dirty" in spots.

Had one like it today. It's almost as though something has scratched the grout in spots, revealing a darker pigment.

Any ideas?

 

[Mikey P]

Dark sand?

 

[safeclean]

Yes it could be contaminated sand or some tilers do not clean there mixing buckets but usually it is the tiler who mixed his grout and did not let it slack for 10 minutes after mixing these black spots are sometimes tiny wholes if you look closely you can see.

When we mix grout and let it slack you will notice all these tiny air pockets coming up thru the grout sitting on top thats what you want than a quick mix and start grouting if they do not do this than tiny wholes will show when the grout cures. Hope that makes sense. The other main reason is the tiler did not clean the joints out first before grout gets installed which will contaminate the grout.

Craig

 

[Gary T]

Yes it is likely they didn't let the grout slake. I have found countless times where the specks are plastic shavings from the bucket. They mix with a drill attachment tearing up the bucket not even thinking the shavings are going into the grout.

 

[Mikey P]

5$ worth of great tips right there.

 

[SJA]

If the black specs are dirt that did not clean up - all I can think of is to try some acid cleaner or colorseal the floor