Replies

1. 
   FNbenthayer | Apr 21, 2005 02:01am | #1

   If the slate is flat and smooth a 5- in one scraper and a brass brush will work. If the surface is very irregular you can try the brush,  but, the slate may flake- be careful.

   The best defense is always choosing a grout that is as close as possible to the color of the slate.

   Jim

    

    

    

    

   The awful thing is that beauty is mysterious as well as terrible. God and the devil are fighting there, and the battlefield is the heart of man.
   - Fyodor Dostoyevski

1. 
   sharpblade | Apr 21, 2005 03:09am | #3

   How about using those specially formulated acids, Works on the grout, and if used sparingly isn't supposed to damage the stone.  I've only used it on small areas/applications, would appreciate comments from folks with more experience. thanks.

   charles a.

2. 
   COremodeler | Apr 21, 2005 03:06am | #2

   "Miracle" Makes a haze remover, I've never tried it and I would be careful using on slate. How bad is it? Good luck

   http://www.miraclesealants.com/

3. 
   woodguy99 | Apr 21, 2005 04:13am | #4

   TSP or Phosporic acid might work if the scraping and scrubbing method doesn't.  As a last resort you could use muriatic acid (aka hydrochloric acid) but be very careful as it's a dangerous chemical.  Plus I'm not sure what it would do to the slate; you'd have to test it first.

    

   Mike

4. 
   coonass | Apr 21, 2005 04:19am | #5

   Murfed,
   Ask here.
   http://www.johnbridge.com/vbulletin/index.php?

   KK

5. 
   neilpuck | Apr 22, 2005 07:26pm | #6

   I'm guessing perhaps that your sub did not seal the tile properly before grouting.   Also best practice is to use a grout bag, similar to a cake decorators icing bag.  I am in the process of tiling a slate bathroom.  Unfortunately, the only solution is elbow grease.  scrub scrub scrub. The only forgiving part is that any scratches in the slate are easily rubbed out.  Don't forget to seal when youre through, and once a year at least.

    

    

6. 
   EdJW | Apr 22, 2005 08:20pm | #7

   Murfed,  Try straight vinegar with one of those sponge/scothbright pads.  I did a lot of slate and that seemed to work fairly well.  It will take a lot of scrubing so have a few packs of the sponges on hand.  When you're done, seal it.  -Ed

7. 
   Karrl | Apr 23, 2005 08:42pm | #8

   I have been in a similar situation and would not encourage anyone else in using this technique.

   I have washed slate and other tile floors with a very high concentration of muriatic acid. I don't remember if I even diluted it with water. You have to wear a respirator or you will trash your lungs and windpipe. The acid will eat your clothes, skin, etc so dress accordingly.

   I used a stiff plastic bristled brush and the acid and any surface grout came off very quickly. I immediately followed up with copious amounts of fresh water and finally sprinkled several pounds of baking soda (big box from costco) over the floor to neutralize any residual acid.

   The fumes will eat the silvering off mirrors in the room, it will tarnish plumbing fixtures, and corrode any exposed metal.

   Additionally the acid compromises the strength of the grout remaining in the joints.

   With all these warnings and disclaimers, I will say the slate floor cleaned up beautifully and the remaining grout joints have held up great. It is indian multi color slate and the acid wash and vigorous cleaning with the brush really intensified the colors. It has been ten years so I don't recall if some of the color variety was lost but the slate still gets a lot of compliments.

   I have used muriatic acid to clean up other tile surfaces over the years and it definitely weakens the grout joints so there is a definite compromise involved. For me the key is cleaning aggressively and quickly and then immediately neutralizing the acid.

   Just remember MURIATIC ACID IS EXTREMELY DANGEROUS. I would not let my wife or kids near the stuff. I have ruined many metal surfaces with its fumes alone and trashed alot of clothing. I advise handling it with the same precautions you would use for a vessel of molten metal.

   If anyone asks I don't advise using this technique. I am just adding it to the mix as something that does work.