efflorescence

Efflorescence is a white, powdery deposit of salts that can appear on the surface of masonry, concrete, brick, or plaster. It occurs when water within or behind the material dissolves natural salts, then moves to the surface and evaporates, leaving the salts behind.

In the context of painting and construction in Australia, efflorescence is a common issue, especially in areas with high moisture or poor drainage. It can affect the adhesion and appearance of paint and coatings, so it's important to address the underlying moisture problem before painting over affected surfaces.

Key points:

• Caused by moisture movement through porous materials.
• Appears as white or greyish powdery stains.
• Indicates potential moisture issues.
• Must be removed and the source of moisture fixed before painting.

Efflorescence is not harmful in itself but is a sign of moisture problems that can lead to more serious structural or aesthetic issues if not treated properly.