Lead marks, or pencil marks, are common after having porcelain tile installed. Sometimes the tile setter does not clean the marks off as well as he should. Other times, the marks reappear after the job is complete because the lead has seeped into the porous surface of the tile. These pencil marks can be difficult to remove, especially after the tile has been sealed or an enhancer has been used.
Fill a bucket halfway with warm water. Add some mild soap such as dish detergent. Use this and the sponge to scrub the pencil marks off the tile. A stiff-bristled brush may be used if the sponge fails to work.
A pencil eraser sometimes will get the job done. If the above step failed to remove the marks, try the eraser. When the tile is dry, simply try erasing the mark. This will sometimes do the trick. If the tile has been sealed or enhancer has been used this method will probably not work.
Use a scouring pad, like the SOS brand, if the above steps have failed to remove the marks. Steel wool may also be used. Whichever you choose, try it first in an inconspicuous place to make sure damage to the tile does not occur.
Take a can of WD 40 penetrating oil and use in combination with a rag or the scouring pad. Again, try this in a small area or on a piece of scrap tile. Don't get the penetrating oil in any grout joints. This will surely leave a stain.
Use acetone as a last resort to remove the pencil "lead" marks. This works most of the time. Apply some acetone to a rag and scrub the marks until they disappear. Even if the tile has been sealed or an enhancer has been applied, the acetone should cut through it. If you use the acetone to remove the marks on sealed or enhanced tile, you will have to apply more sealer or enhancer after the acetone has evaporated.
Use gloves when working with acetone. Use safety glasses when working with acetone. Use acetone in a well-ventilated area. Always test methods on scrap tile or in an inconspicuous area.
Obey the warning label on the acetone bottle. Don't get acetone in open cuts. It will burn. Keep acetone away from children.