Replies

1. 
   Guest_ | Feb 15, 1999 10:03am | #1

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   Chlorine bleach will soften portland-based grout. Give it some dwell time of 20-40 minutes before scrapping. Still requires elbow grease, just less than before.

   The only downside is that you will be harming the grout you want to keep in place.

   If you don't want to go this route, I suggest keep doing what you are doing...again and again and again, until you are either satisfied or worn out. Be sure to agitate the acid to get maximum effect. And keep the grout wet. Persevere.

1. 
   Guest_ | Feb 15, 1999 11:28pm | #2

   *You may want to seal the "good" grout prior to using solutions to strip the bad grout. It may help reduce the amount of damage caused to the grout you want to keep in place.

1. 
   Guest_ | Feb 16, 1999 02:13am | #3

   *I should think sealing the grout would be a waste of time and money. To remove unwanted grout involves mechanical scraping and/or the use of harsh chemicals. The trick here is for him to selectively remove grout. If it were me, I'd flood the floor with bleach--be sure to ventilate to outside--, give it some dwell time, scrap, scrap, scrap, not worry too much about saving the grout in the joints, cleanup the floor with copious amounts of clean water, let dry, re-grout. While it is quite feasible to save the existing glazed tiles, care must be taken not to scratch the glazed face of the tile. Mostly, this means not using power equipment. I imagine a floor buffer could be used, but I'm not sure what good this would do as it would tend to ride up and over the unwanted grout. Perhaps a low RPM setting would be more effective. Perhaps a call to a janitorial service would be in order here.

2. 
   Andy_Campbell | Feb 16, 1999 07:55am | #4

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   From experience I would say to use Muratic acid. Sparingly!Wear goggles and gloves!Knee pads will make this often long process bearable.Use a small stiff brush and keep away from the grout lines. If you have a small area or have alot smeared around then remove as suggested above.

3. 
   Guest_ | Feb 16, 1999 09:10pm | #5

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   And a respirator with acid approved filters.

4. 
   tedd | Feb 17, 1999 12:04am | #6

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   Did you try the coarse grade of grout cleaning scrubbie. Its tough and works when most other abrasives won't and it won't damage the tile.

   I don't know if you can get this material the sized and shape you need for a rotary floor scrubber.

5. 
   Peter_Kemp | Feb 17, 1999 12:04am | #7

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   I grouted (Custom sanded grout) a week ago, and ran 0ut of time before wiping down excess.

   Disastrous!!! Today I tried a rotary floor scrubber with heavy duty pads, and full strength (from bottle, anyway) phosphoric acid, and 16 oz. of sulfamic acid in 1 gal. of water.

   Got some off, but the streaks of crud are unbelievably hard, even to scrape with a drywall knife.

   Does Anyone know of a solvent that will loosen this crud??? The tile is glazed, with a slight texture.