Chalking is the formation of fine powder on the surface of the paint film during weathering, which can cause the appearance of change in colour. 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 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. Dulux recommends Dulux Weathershield® for exterior surfaces. For more information, please consult our detailed Technical Advice note on the topic.


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