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Old 04-27-2005, 08:47 AM   #1
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Unhappy Hardened Grout on slate

I recently installed a slate floor in my basement and didn't clean up the grout in time. It has hardened over most of the tiles and is not coming off. I have tried using 50/50 vinegar solution, straight vinegar, and last night after waiting for 12 days for the grout to cure I tried sulfamic acid. Neither has been able to take the grout off. The slate was made in Inida, I bought it from Lowes. What could my next possible steps be? Can I try a stronger acid? Or, another option is that the floor doesn't look so bad when it is wet, I used a grey colored grout so when it is wet it looks like a dark grey and blends in better with the slate than when dried. If I enhance and seal it will it retain the dark color? If not, does anyone know anyone who offers Slate cleaning services in the Gaithersburg, MD area?
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Old 04-27-2005, 01:58 PM   #2
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Hi There,

What would you like for us to call you?

Anyway, this problem is going to be a tough one to fix. The hardened grout on a cleft surface is quite difficult to remove.

It involves using something like a wooden dowl or anything wood or plastic with a rigid tip that you can use to scrape the grout.

The amount of time that has elapsed means the grout is pretty solidly locked in place. You can try using a lot of water in the areas you are scraping to make matters easier but not easy.

To color enhance the material and grout is something I am not going to advocate. Yet, if it looks fine to you, this will be simplest solution. The grout may overtime abrade off with foot traffic and you will probably need to maintain the enhanced product more rigorously to maintain the look. This may mean periodic reapplication of the color enhancer, as well as washing the floor frequently.

Good luck.
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Old 04-27-2005, 02:16 PM   #3
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Thanks for the reply, My name is James. The grout is definitely locked into place. I will see if I can get some pics taken and uploaded so you can get a better idea of how much damage is done. Do you think using a stronger acid would help loosen up the grout? I am not sure what the next step up from Sulfamic is, but I am also not sure if it will make that much of a difference. I can live with a little grout in the clefts, but on some of the tiles I would say that 80% of the surface is covered. I will pick up a wooden dowl tonight and see how much a difference that makes.
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Old 04-27-2005, 02:56 PM   #4
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James --

The acid actually dissolves some of the cement in the grout. When it is first applied, you should notice bubbling as the chemical reaction proceeds. When the bubbling stops the chemical reaction that converts the alkaline cement and acid into water and salts has stopped. At that point you should clean up the liquid and re-apply. Scrubbing with a stiff brush and using a tool like Steven suggested should also help.

Try a few repeated treatment on a test area and see if that works.

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Old 04-28-2005, 11:21 AM   #5
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Hi James, Welcome!

Slate cleanup is a tough one. We just completed a large job, and had success with plastic putty knives, three in one tools, utility knives, and Prosoco's SafEtch http://www.prosoco.com/Product.asp?ID=239

Last, but not least a torch. I highly recommend testing this method outside on a sample before using indoors.
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Old 04-29-2005, 07:21 AM   #6
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Thanks for all the advice, I haven't had time the past two nights to try to clean it some more, but the weekend is completley free.

Jdm, Thanks I will try your suggestion tonight, along with some wooden dowls and plastic putty knives...

doitright, someone else had mentioned to me an etching product that was called dry etch...I tried to find it at homedepot, but they had never heard of it. I will look for safetch at this masonry place by my house. What is a 3 in one tool? and I don't think I will try this, but what did the torch do?
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