The formation of fine, white powder on the surface of exterior paint film due to weathering.

The chalky residue can make your paint appear faded, but it's actually an ideal way for paint to weather because it's easy to remove (see steps below.) However, excessive paint film erosion may result in heavy chalking.

Paint chalking can be the result of a number of causes including:

• Paint composition. Oil-based paints tend to chalk more than latex formulations.
• Use of a low-grade, highly pigmented paint.Use of an interior paint for an outdoor application.
• Use of factory-finished siding. It can develop an excessively thick chalk layer and may require power washing to ensure complete chalk removal.
• Not adequately sealing a porous surface.
• Over thinning a paint or stain.
• Spreading the paint too thin.

Remove chalk residue by rinsing or power washing the surface with an appropriate cleaner. If some paint chalk remains after first washing, then wash again for complete removal. Scrubbing may be necessary.

Rinse well with clear water. Allow to dry thoroughly. 

Brick areas that are stained by "chalk run-down" should be scrubbed with a stiff brush and detergent. Professional cleaning may be required to remove this staining.