Chalking: Formation of 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 from heavy chalking. Possible causes: Use of a low-grade, highly pigmented paint. Use of an interior paint for an outdoor application. Remedy: First, remove as much of the chalk residue as possible, scrubbing with a stiff bristle brush (or wire brush on masonry) and then rinse thoroughly; 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 acrylic 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.