Sep 10, 2020


  • Efflorescence consists of soluble salts formed on the surface of plaster or brickwork by the evaporation of water. They usually show as loose white powder or as feathery crystals. Occasionally they appear as a hard glossy deposit covering and penetrating the surface. Efflorescence can occur on internal as well as external surfaces and is often a mixture of different deposits.

These salts may have come from:

  • The brickwork,
  • Soil in contact with the brickwork,
  • Contamination with seawater or spray.

Efflorescence may damage plaster and paint if these are applied before the walls have dried out.

While efflorescence persists it is unwise to apply paint. Persistent efflorescence indicates abnormal water penetration of the brick and plasterwork.

Any faults in construction must be corrected, i.e. leaking water pipes, faulty damp-proof courses.


Masonry, gypsum plaster.


    • No remedy is available for Efflorescence; the only way to prevent it from occurring is to prevent damp from entering the structure that will allow efflorescence to occur. Once it has occurred, allow it to dry out (less than 15% moisture contents) and scrub the crystals off with a nylon or wire brush. Should the efflorescence reoccur, continue to brush the affected area.
    • When no more efflorescence has appeared prime the affected area with Rainbow Fresh Plaster Primer and allow drying for 24 hours.
    • Then apply the selected Rainbow Paints topcoat.