Black grout has turned grey [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile


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02-17-2010, 07:52 AM

I'm looking for some advice to a problem. This was the first time I've applied a colored grout, my only other experience was doing the bathroom shower tile. (Which came out great.)

Last night I tiled black granite with Polyblend #60 Charcoal Nonsanded Grout. When I woke up this morning most of the grout was a lighter grey color, but there are some patches where the grout is black (but not many.) I mixed the grout with a mortar mixer on the end of my drill so I know it was well mixed. After I applied it with the float I noticed that in many places it wasn't so smooth so I used a damp sponge and water on my finger to smooth out the grout after I filled it in. (Was this a no-no? What have I done wrong and how can I fix it?


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02-17-2010, 10:35 AM
Typically, lighter grout means too much water used during cleanup. Sounds like you've already confessed to the crime. :D

Most cases, the grout color underneath the surface is correct, so you just have to remove some of the surface material. Use vinegar and a stiff nylon brush, scrub the grout until you see a change of color, then rinse off with clean water. It may take a couple or more scrubbings to get the right color.

02-17-2010, 11:20 AM
Thanks for the reply.

Yes, guilty as charged! I'll try scrape off the surface layer.

If I scrape some off, is it ok to apply another thin layer of grout on top?

Thanks again!

02-17-2010, 11:23 AM
You won't need to do that. The amount of grout you need to remove is about 1 grain of sand thick. Maybe 2 grains. It won't be noticeable.

If you really need to re-grout, remove grout down to 1/3 of the tile thickness.

02-17-2010, 05:39 PM
Or just use a grout colorant/sealer in a black and wipe on wipe off while the grout is still unstained and porous. Might match closer then the charcoal too.