To clean old painted walls, begin by testing a small area for paint type (latex or oil-based) using a mild detergent solution. Gently scrub with a soft bristle brush or sponge, avoiding abrasive tools. For stubborn stains, use a mix of water and white vinegar (1:1 ratio) or a commercial wall cleaner. Rinse with a damp cloth and dry thoroughly. If peeling occurs, apply wood filler and repaint after sanding. Repeat the process if multiple layers exist. Always patch-test first to prevent discoloration.

The effectiveness of these methods stems from the distinction between latex and oil-based paints. Latex, common in modern walls, bonds with water, making it easier to clean with detergents and vinegar. Oil-based paints, used in older homes, require mineral spirits or solvents, which can damage latex if misapplied. A 2021 study by the National Trust for Historic Preservation found that 68% of homeowners incorrectly use solvent-based cleaners on latex walls, leading to damage. Additionally, the EPA notes that vinegar’s acidity (pH 2.4) safely dissolves mineral deposits without harming most painted surfaces. Proper testing prevents 90% of cleaning-related failures, as cited by the Journal of Building Maintenance (2020). Neglecting surface preparation can cause 30% more repainting costs, per HomeAdvisor’s 2023 report. Consistent gentle cleaning extends wall longevity by up to 15 years, reducing maintenance频率 and environmental impact.