Things You'll Need
Children's molding dough (Silly Putty)
Coarse scrub brush
Don't let the white vinegar sit too long on the painted brick fireplace or it could damage the paint. Scrub in the vinegar for a few seconds, then rinse quickly to minimize the chance of damage.
When all else fails, a fresh coat of paint will cover up most any soot stain. However, don't just slap a coat of paint on and hope for the best. Soot stains must be primed first or they will almost always bleed through. Use a stain-blocking latex primer or a can of Kilz oil-based stain blocker to cover the soot before you paint.
Never use mineral spirits, nail polish remover, alcohol or harsh chemical cleaners to remove soot from a painted brick fireplace as these may damage the paint.
Most of the time, it's no real trouble removing soot from a brick fireplace. All you need is chemical cleanser and a coarse brush. However, when the brick fireplace is painted, you must use great care or you'll likely damage the finish, or at bare minimum, cause some discoloration. More often than not, people get too aggressive when trying to remove soot stains from a painted fireplace. This often results in the entire fireplace having to be repainted. If you need to remove soot from a white painted brick fireplace, there are a few techniques you can use that may save you from having to re-coat the entire surface with a fresh coat of primer and paint.
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Press the children's molding dough or Silly Putty against the soot stain, then pull the dough away. It should remove some of the soot. Repeat until all of the soot has been removed. If this fails, use dish soap and warm water.
Mix ordinary dish soap with warm water. Use a coarse scrub brush to apply the soapy water to the soot stain. Scrub in a circular counter-clockwise motion. Rinse the surface with a wet rag. Proceed to Step 3 if any soot remains on the painted brick fireplace.
Mix the white vinegar with water (1/3 vinegar, 2/3 water). Use a coarse scrub brush to apply the vinegar to the soot stain. Scrub in a circular counter-clockwise motion. Rinse the surface with a wet rag. Repeat until all the soot has been removed.