One sure way to ruin a tile job and make it look unprofessional is to have dried grout all over the top of the tiles. However, just because the grout is dried, doesn't mean you can't fix the problem. No special chemicals or solutions are required. By applying water to the surface, it will soften the grout and make it easy to scrape and wash off of the tile. The amount of time to complete the job varies depending on how big and how severe the problem is.
Fill a bucket with warm or cold water. Pour some water over the tile containing the dried grout. The water will help prevent tiny scratches on the surface of the tile.
Rub the tile with the tip of the wood paint mixing stick to dislodge the dried grout. Only a small amount of pressure is required.
Rinse the tile and wipe it clean with a rag to remove the grout particles from the surface.
Dip the nylon scouring pad in the water, then pour some clean water over the tile where you just scraped off the grout using the stick.
Scrub the tile with the nylon scouring pad. Apply clean water while you scrub to prevent scratching the tile surface. Rinse the tile with clean water and dry the surface with a towel. If there is still a film of grout on the surface of the tile, apply more water and continue scrubbing with the nylon pad until you are satisfied with the result.
If the grout is epoxy based, removal of excess grout is virtually impossible. Most grouts are not epoxy based and are instead made out of Portland cement, so this removal technique is effective most of the time. If you are unsure of what kind of grout you have, consult the grout mix packaging if you still have it. While wood paint mixing sticks work well for scraping off the dried grout and can be had for free in the paint departments of home improvement stores, any flat-tipped piece of wood will do.
Do not use any metal tools to scrape excess grout off of tile because they will scratch and damage the tile.