Frosting

 

A white salt-like substance which appears on the paint surface, and is more noticeable on dark colours.

A white salt-like substance which appears on the paint surface, and is more noticeable on dark colours.

Causes

  1. Calcium carbonate-based paints/85 which are exposed to high humidity. The problem occurs mostly in humid and weatherproof areas such as porches, gutters, etc.
  2. Painting applied on a coating that has been formulated with calcium carbonate.

Solutions

  1. Also for cause 2: If the problem is minor, clean the surface and apply a new coat of paint. If the problem is serious, clean the surface and apply a solvent-based primer before adding two coats of paint.
  • On masonry, this problem can be mistaken for efflorescence: frosting appears on the coating whereas efflorescence appears under the coating.