Paint Chalking

The chalking of paint results when a paint film gradually weathers or deteriorates, releasing individual particles of resin and pigment which leave a fine powder on the paint surface. Most paints chalk to some extent, which is desirable because chalking cleans the painted surface. However, chalking is objectionable when it washes down over a surface with a different color or when it causes premature disappearance of the paint film through excessive erosion. With colored or tinted paints, chalking is a common cause of fading.

For repainting surfaces that have chalked excessively, proper preparation of the old surface is essential if the new paint coat is expected to last. Scrub the old surface thoroughly with a detergent solution to remove all old deposits and dirt. Rinse thoroughly with clean water before repainting. Discoloration or chalk that has run down on a lower surface may be removed by vigorous scrubbing with a good detergent. The discoloration will usually weather away with time if the chalking problem on the painted surface has been corrected.

Resin Exudation

The exudation of resin from knots can cause discoloration problems usually associated with painted wood and solid-color finished wood, but can also be a problem with semi-transparent stains. The knots in many softwood species, particularly pine, contain an abundance of resin. The resin can sometimes cause paint to peel or discolor.

Good painting practices can help minimize or control staining over knots. It is most important to apply a primer to the bare wood specifically recommended for the control of knot resin bleeding, and then apply two topcoats. These specialty primer paints work best under high-quality acrylic latex topcoat paints. In fact, research has shown that a poor topcoat paint will negate the effects of a good primer paint for controlling knot and other resin bleed.