Chalking is the weathered powder found on exterior painted surfaces and is a normal way for paint to weather away. However, premature chalking can be caused by inadequate priming or thin paint. Homeowners should be aware that chalking on siding located above masonry will run during rainy weather causing the masonry to stain. Once a chalked surfaced is pressured washed clean and prepared for painting, one coat of a top quality alkyd primer and one coat of a top quality acrylic latex finish paint is highly recommended for the prevention of future excess chalking.