Soot leaves greasy residue that can prove difficult to remove from stucco surfaces. Whether caused by small fires or stovepipe emissions, soot stains cannot be cleaned from porous stucco walls with ordinary soap and water. Chlorine bleaching agents can damage the cement composition and alter the color of stucco. The best solution is an oxygen bleach cleaner, which will remove the stain and leave the stucco looking fresh and clean.
Brush the soot-covered stucco wall with a broom or cleaning brush. Wear a dust mask during this process to avoid inhaling the soot.
Mix one cup of powdered oxygen bleach cleaner with a full bucket of water. This product is available from any hardware store or home improvement center.
Apply the mixture to the soot-covered stucco using a scrub brush, then gently scrub the solution into the stucco. Allow the cleaning mixture to sit on the wall for 10 to 15 minutes.
Rinse the solution off an exterior stucco wall with a garden hose. Rinse an interior stucco wall using a rag soaked in clear water. Allow the wall an hour to air dry.