Frosting

Possible Causes

• Forms mostly in protected areas (such as under eaves and on porch ceilings) that do not receive the cleansing action of rain, dew and other moisture.
• Use of dark-colored paints that have been formulated with calcium carbonate extender.
  Application of a dark-colored paint over a paint or primer containing calcium carbonate extender.

Solution

• Frosting can be a stubborn problem. It often cannot be washed off readily. Moreover, the condition can recur even as a bleed-through when a new top coat is applied. In extreme cases, it can interfere with adhesion. The best remedy is to remove the frosting by wirebrushing masonry or sanding wood surfaces; rinse, then apply an alkyd-based primer before adding a coat of high quality exterior paint.