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Grout stained my tile

1110d's picture

We just put down a slate tile floor.  We want to use two different colored grouts.  I started with the darker color, a barn red.  I sponged off the excess and then cleaned the tiles a second time with clear water.  Even after dusting, the tiles still have very faint red hue to them.  You really can't pick out the red so much as the slate tiles have now lost their color.  The floor looks much flatter and doesn't have the natural color variations it once had.  How should I clean this extra color off?  Would a mild acid wash do the trick?  If so, should I use muriatic, viniger or the grout cleaner I saw at the home center?  Is there something else I should try first?

The next step will add the second grout color.  She has picked a natural grey.  Should I just slap the grey on over the red or should I try to mask the red grout off?


Certified boat fetish.

(post #105858, reply #1 of 14)

Did you seal the tile before grouting?  You should have.  I imagine the red pigment is iron oxide, which stains everything.

Muriatic/Hydrochloric acid might work.  The home store might have it, but a real tile store would have it for sure.  And not too mild a solution.

(post #105858, reply #2 of 14)

Yes, I applied a pre grout sealer.  I'm concerned about the acid because I've seen it change the color of mortar in the past...  Yes, the red even stained my ceramic lined sink and buckets.  A quick hit with the scrubbie would take it off (the bucket is hopeless), but if the surface wasn't flushed with water while scrubbing the color would just adhere somewhere else.  In the sink it looks just like a red soap scum ring.  For some screwy reason it changed my yellow sponge green and even changed the color of grout trowel!


Certified boat fetish.

Edited 3/12/2008 9:34 pm ET by 1110d

(post #105858, reply #3 of 14)

I'd start with the mildest remedy first.  Try vinegar and a Scotch Brite pad.  If the slate becomes dull the color of the slate can be restored with a sealer.

(post #105858, reply #4 of 14)

distilled white vinegar, scrubbie pad and elbow grease....


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(post #105858, reply #5 of 14)

it's probably not stained ...

most likely just more haze that has to be removed.



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    Buck Construction

 Artistry In Carpentry

     Pittsburgh Pa

(post #105858, reply #6 of 14)

Thinking about this a bit further (maybe thinking about it too much), the acid will be dissolving the mortar.  What if this just some of the red pigment and that pigment doesn't react to the acid?


Certified boat fetish.

(post #105858, reply #8 of 14)

The grout manufactures make a Haze remover. It is an acid, but not acetic or hydrochorlic.

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(post #105858, reply #11 of 14)

The haze remover is generally sulfamic acid (but he should use the haze remover specified by the grout manufacturer, which may or may not based on sulfamic acid).  I think they sometimes they use phosphoric acid, too, but I'm not sure.


Edited 3/14/2008 10:45 am ET by Billy

(post #105858, reply #12 of 14)

Ok, the grout mfr. suggested I start with a "Nanoscrub" product.  Apparently this product is Ph neutral but contains a fine grit which physically scrubs the color off.  It didn't work.  I then tried vinager.  Didn't work.  I went to the local big box and the guy helping (who actually seemed to have a knowledge base) suggested I skip over the grout cleaner and go to a sufanic acid.  The acid helped.  I tested on the color stain in my bucket and it zipped the color right off.  Unfortinatly, the tile is more porous than a plastic bucket so it only lighted the red.  There is no question the tile has less color, but we still have a long ways to go.

Because I have not finished grouting, I'm nervous about using muriatic acid for fear of weakening the thinset.  The water will want to run into the open grout lines and will just eat away at the mortar.  I'm also hesitant to continue grouting for fear the red will then stain the natural grout when it's cleaned.  Does the board have any other suggestions?


Certified boat fetish.

Edited 3/14/2008 9:04 am ET by 1110d

(post #105858, reply #13 of 14)

Yes, go to and ask over there.  They know tile and stone.  You may even want to ask in the Pro hangout there.

You probably should finish grouting before you try any surface treatment, as you may get some color change in the grout.  Also, you don't want the slate to be different colors in different parts of the room, beyond the natural variaitions in slate color.

It sounds like a tough problem.


(post #105858, reply #14 of 14)

Done deal.  Thanks for the tip.


Certified boat fetish.

(post #105858, reply #7 of 14)

Why two colors of grout? Please enlighten me what that will achieve. What kind of effect will the combination make?

(post #105858, reply #9 of 14)

The effect will be simular to a plad.  We used 6x6 tiles with 1/2" and 3/16" joints alternately.  The smaller joints are red and the larger ones will be grey.  Although I typically prefer a tight joint, the different sizes actually looks really good. 


Certified boat fetish.

(post #105858, reply #10 of 14)

The effect will be simular to a plad

Why didn't you say so earlier?  With the grout color bleed, now you have madras............a time honored tradition-if not a bit Indian.

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