Frosting: A white, salt-like substance on the paint
surface. Frosting can occur on any paint color, but it is
less noticeable on white paint or light tints. On masonry,
it can be mistaken for efflorescence see Efflorescence and
Forms mostly in protected areas (such as under eaves and
on open 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.
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