Chalking

Formation of a fine powder on the surface of the paint film during weathering, which can cause colour fading. Although some degree of chalking is a normal, desirable way for a paint film to wear, excessive film erosion can result in heavy chalking.

Possible Cause

• Use of a low-grade, highly pigmented paint.
• Use of an interior paint for an outdoor application.

Solution

First, remove as much of the chalk residue as possible, using a stiff bristle brush (or wire brush on masonry) and then rinse thoroughly with a garden hose; or use any power washing equipment. Check for any remaining chalk by running a hand over the surface after it dries. If noticeable chalk is still present, apply a quality solvent-based or water-based primer (or comparable sealer for masonry), then repaint with a quality exterior coating. If little or no chalk remains and the old paint is sound, no priming is necessary and the surface can be repainted with a quality exterior paint.

Images courtesy of the Paint Quality Institute from Dow Coating Materials

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