Cleaning a Soot-Covered Brick Fireplace Face
Oils and soot make an otherwise handsome brick fireplace face look tired and tattered. To reduce the effect of oils and soot, regularly vacuum a brick face and hearth and periodically wipe them down with a damp sponge. Also, you can prevent smoke from staining your fireplace face by elevating the fire; simply add a layer or two of firebrick at the bottom of the firebox.
If the hearth is soiled to the extent where you can no longer determine what material it is constructed from, then it's time for a more serious cleaning.
All you need is a 10 percent solution of muriatic acid. (That's 1 part muriatic acid to 9 parts water. Add the acid to the water.) Use a bristle brush to clean the affected area and rinse with fresh water. More than one application may be required for extra dirty areas.
Working with acid is dangerous. Be sure to wear rubber gloves, safety goggles, and have plenty of ventilation.