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Removing thinset from inside bathtub

CaseyR's picture

Just had new tile laid on the bathroom floor. The installer did a good job but his helper apparently cleaned his tools in the bathtub and left a large mass of thinset or mortar in the bathtub. Unfortunately, I did not find it until the next day. I was able to remove about 90% of the stuff, but there is a large gray spot about a foot in diameter and an area about half that size with pronounced black streaks. I think the stuff was modified thinset.

I did a web search, but got lots of sites that tell me how to remove grout from around the tub when removing the bathtub - but nothing on getting the stuff off the bathtub when it is spilled inside.

I have some Bon Ami that I am about to try, but I would assume that even Bon Ami is likely to remove the sheen from the porcelain if I scrub too long and hard. Anyone have any magic pixie dust to make this stuff go away?

The guy behind the counter at the tile shop suggested trying X-14 cleaner, which I will try and locate. I have my doubts, however, that it will do much good. Probably try some strong oxidizing cleaner to ee if that will at least lighten the dark gray areas.

(post #105780, reply #1 of 22)

C.R.L. Cleaner?  I'm surprised that the tub even drains now!

(post #105780, reply #2 of 22)  Removes all kinds of stains. It works great and won't damage your tub.


(post #105780, reply #3 of 22)

You need to break the bond that is assisted by latex first.

Look at Goof-Off products by the paint strippers and cleaners.


EDIT - Actually, you need to call numbnuts and his boss back to the house FIRST before you do anything else.  They fix it or... or they fix it.



Rebuilding my home in Cypress, CA

Also a CRX fanatic!

If your hair looks funny, it's because God likes to scratch his nuts.  You nut, you.

Edited 2/28/2008 11:39 pm by xxPaulCPxx

YAY!  I love WYSISYG editing!  And Spellcheck!


(post #105780, reply #4 of 22)

Being deaf and depending upon email for communication tends to slow response considerably. I did sent an email yesterday, so we shall see what response is forthcoming.

I will give both the Bartenders Friend (I have some stored away somewhere) and the Goof-off (I think there are supposed to be two versions of Goof-Off, but I have the most commonly available one). Not sure what order to try them. Hopefully they will not, in combination, dissolve not only the grout but my bathtub as well...

(post #105780, reply #5 of 22)

""Hopefully they will not, in combination""

BE CAREFUL and READ the ingredients.

Combining any number of household cleaners and spot removers can cause dangerous gases to be formed.

Best to use one product , rinse well, rinse again and then apply the second product if you have any doubts about interactions between products.

They can't get your Goat if you don't tell them where it is hidden.

Life is Good

(post #105780, reply #10 of 22)

   Casey try denatured alcohol to cut the latex modifier. Again use a rag to keep it wet for a while.

(post #105780, reply #11 of 22)

and air dry the rag before ya toss it...


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Forget the primal scream, just ROAR!!!

"Some days it's just not worth chewing through the restraints"

(post #105780, reply #21 of 22)

An ex of mine used to be a professional new construction cleaner.  That's the stuff she used. 

I've also had good luck with mild acids like vinegar, since it eats the sand and cement making the synthetic portion easier to remove.


Beer was created so carpenters wouldn't rule the world.

If I could edit my location it would say I'm now in Reno :-)

(post #105780, reply #6 of 22)

I would first try an acidic substance like white vinegar. Put a rag on top to hold the vinegar on and keep it wet for awhile. The acid should help break up the mortar. I've cleaned tools like this that sat too long.

If you want to kick it up a notch, there's muriatic acid, but i'm not sure what it would do to your tub.

(post #105780, reply #7 of 22)

Muriatic acid should do it. Keep it wet and let it soak in. Repeat. Scour with a plastic scouring pad.

(post #105780, reply #8 of 22)

i agree, this isn't your problem. allow them to make it right. if they refuse document. then maybe you try. if you jump gun with out allowing them to formally refusekk , you may relieve them their liablilty.

(post #105780, reply #9 of 22)

I would be careful with muriatic (hydrochloric) acid as it may etch the tub. Vinegar may work, but anything that will attack thinset will probably also attack the porcelain finish on the tub. Goof-Off sounds like a good idea too. Or alcohol. As always, start with what wil be the least harmful to the tub finish and go stronger if necessary. The solvents like Goof-Off and alcohol are the least likely to attack the tub, but even vinegar may etch the surface if left on too long.

(post #105780, reply #12 of 22)


I would agree that the tile setters are responsible for replacing your tub.

If that's not possible then I would look for a tile of tub cleaning product that has phosporic acid in it. It is mild enough that it won't eat your finish.

Phosporic acid is the ingredient in naval jelly. You can use it straight or thin it with water. Warm water makes it work better. Let it sit on the spot for a time before trying to scrub.

If you know a Conklin dealer then get some Multipurpose Surface Cleaning Gel.

Our plumbing retail outlet (Handyman) carries a similar Phosporic acid based cleaner but I don't have a bottle around right now.

If the product is made to clean toilets then it is too strong and stay away.

I don't think you mentioned if it is a cast tub or acrylic.

If it is acrylic I would be careful with the solvents. I burned a tub surround with either Goof Off or Goo Gone, can't remember which it was now. Not a pleasant experience.

Good luck.


(post #105780, reply #13 of 22)

I tried the Bartender's Friend and it worked amazingly well. I didn't even try the Goof-Off. I think the Bartender's Friend is probably even less abrasive than Bon Ami, but it works. Got it at the local Target store but the website for the stuff said it was also available at Safeway and Albertson's. I had heard good things about it, but this was the first time I ever actually put it to the test.

(post #105780, reply #14 of 22)

Barkeepers Friend is more aggressive  then Bon Ami.  Bon Ami wont scratch Stainless steel, Barkeepers friend will although very very fine scratches.  So don't use it on a Range hood,  Neither will scratch porcelain.  That is what I found when cleaning baked on stuff off my SS range. 

(post #105780, reply #17 of 22)

There is a liquid version also sold as a stainless steel sink product.  Both rock.

edit: used to be called shiny sinks plus

Edited 2/29/2008 7:36 pm ET by rasconc

For those who have fought for it Freedom has a flavor the protected will never know.

(post #105780, reply #18 of 22)

BTW, BKF has oxcialic acid in it. Great for stains.

Until you posted this I would not think that it would be that good on grout.

BTW if you have some that still can't get off, check the grout manufacture. They have a grout haze remover which is acid based. But I don't know which acid off hand.

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(post #105780, reply #19 of 22)

I had a great experience with BKF.  After flushing out the plumbing lines into the tub, little specks or stains were left from metal pieces.  BKF took them right out.

(post #105780, reply #20 of 22)

Bill -
I asked about the acid based tile cleaner at the tile shop and they said that it would take the sheen off the porcelain of the tub, so I ruled that out.

(post #105780, reply #15 of 22)

Why do people write about what other people did? Thats not your problem. I'd say the best way to get the thinset off of the tub would be withholding the check, sit back and watch the thinset disappear.


Family.....They're always there when they need you.

(post #105780, reply #16 of 22)

I'd be more worried about the thinset in the trap and drain pipes..... How do you remove that?

(post #105780, reply #22 of 22)

Vinegar.  Let it soak a long time.