It actually works!  Dried grout on tile.
I bought this in a desperate attempt to clean off over-worked grout.  Foolishly I grouted late at night  (base tile) and didn't bother cleaning it off.  Big mistake.  I was left with smeared dried grout on my tile that would not budge.  There were other projects that needed to be done, and I wanted to finish the rest of the tile - so I just left the base tile as is for several weeks, figuring I would get to it when I get to it.  I discovered that cleaning off dried grout is nearly impossible.  I tried an acid based cleaner that did very little, and even the "sugar water" trick.  Surprisingly that did help a bit, but was too much scrubbing work.  THIS product worked like a charm!  I can't believe how well it works.  I wish I had before and after photos to post.  Spray it on, leave it for 20 minutes, then use a scotch brite pad.  I also had to use a plastic scraper in certain heavy areas, but now my tile is clean!  The really bad areas like the corners needed two applications, but it worked.  I don't know how this will perform for other issues, but for dried grout - this is the one!
Rating: 5 stars