A fine powder can occur on the surface of the paint film during weathering, which can cause color fading.
What Causes It?
Although some degree of chalking is a normal, desirable way for a paint film to wear, excessive film erosion can result in heavy chalking.
The use of a lower-quality, highly pigmented paint or an interior paint can cause the paint to erode prematurely and cause chalking.
How to Solve It
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 oil-based or acrylic latex primer (or comparable sealer for masonry).
Repaint with a quality exterior coating. If little or no chalk remains and the old paint is sound, no priming is necessary.
Note: Images provided by The Rohm & Hass Paint Quality Institute.