Have you noticed white, powdery stains forming along the bottom of your interior walls or basement? That’s most likely efflorescence, commonly referred to as white mold or saltpetre. While it’s not toxic, it’s a sign of serious moisture issues in your walls. The good news?
Efflorescence is a crystalline deposit of mineral salts (mostly potassium nitrate) that forms when water rises through the walls from the ground (called rising damp). As the moisture evaporates, it leaves behind white powdery traces on the surface.
White or grayish powdery stains on interior walls
Paint or plaster that flakes or bubbles
Persistent musty odor
Cold, damp-feeling walls
Scrub the area with a stiff brush or metal scraper
Vacuum the debris to avoid breathing in the dust
Apply a homemade cleaner:
🧴 Mix white vinegar with warm water, or baking soda with water
Let it sit for 10 minutes, then scrub again and rinse
These specialized products break down and stabilize the salts inside the wall.
✅ Apply to clean, dry walls
✅ Use gloves and ventilate the space
✅ Follow product instructions carefully
Improve air circulation (open vents, install extractor fans, or use a VMC system)
Check for leaks or poor drainage outside and inside
Consider a dehumidifier for persistent humidity
For older homes: consult a professional for anti-rising damp treatment
✔️ Don’t place furniture directly against damp-prone walls
✔️ Avoid using waterproof paint — it traps moisture inside
✔️ Use breathable paints or lime-based plasters
✔️ Air out your kitchen and bathroom daily
In short, efflorescence isn’t dangerous, but it’s a red flag. It means your wall is “sweating” minerals due to hidden dampness. By tackling both the symptom and the source, you’ll protect your home’s structure and air quality — without expensive renovations.
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