QUESTION

How to Clean Grout off of Slate? - Looking for products/advise to remove dried excess grout from outdoor slate tiles.

ANSWER

ANSWER - To clean a cementitious grout off of a natural slate stone, you need to carefully chisel off any large chunks of grout.  To remove the grout haze you should use a diluted sulphamic or phosphoric acid with a bristle brush.  Make sure you wet the surface of the slate first before applying the acid.  Make sure afterwards that you flush the slate with clean water to remove any acid.  It may be best to use a wet and dry vacuum to pick up the water for control.

Follow manufacturers' directions in the use of their cleaner.  Test an out of way spot first to make sure you get satisfactory results before proceeding on the whole floor.  For a list of manufacturers with links to their website, who produce acid cleaners, visit our website at www.CTaSC.com and go to Expert Answers where you'll see Resources, then click  Cleaner and Sealers page.  Good luck.