When you install ceramic tiles, you usually use Portland cement to attach the tiles to your floor or wall. If you apply too much cement, it seeps up in between the tiles and then overflows onto the tiles. Once cement hardens, it is very difficult to remove. If you want to take out a tile or apply new grout, a rotary tool can help you completely remove cement grout.
Fill a bucket with water. Pour a generous amount of water over the section cement grout you wish to remove.
Scrub gently but firmly over the surface of the tile with a synthetic scouring pad. Focus on the area where excess grout is sticking to the tile. Rub in a back and forth motion to loosen the grout from the surface of the tile. Continue to pour water over the tiles as you scrub them; don't let your scouring pad dry out.
Pour clean water over the tiles you have scrubbed and dry them with a paper towel. Check to see if you are actually removing the grout. If the grout is not coming off, apply more pressure on the scouring pad.
Remove the grout in between the tiles using a rotary cutting tool. Insert the rotating blade of the tool between the ceramic tiles and cut into the grout to break it up. Work carefully and try to avoid nicking the ceramic tiles with the blade of the rotary tool. You can use a Dremel grout removing tool with a 1/16 carbide bit.
Insert a thin nail in between the ceramic tiles. Rake the nail across the broken grout. Use the nail to push the grout out to the surface of the tiles. Sweep the grout off the tiles with a broom.
Apply a grout release agent after installing the tiles to make removing cement grout easier.
Think twice before you use acid to remove tile grout, since acid can change the colour of your tile.