It is commonly believed that masonry surfaces such as concrete, stucco, common brick and concrete blocks are painted only for decorative purposes. These surfaces, because they are somewhat porous, are painted or finished many times for protective purposes to keep out moisture and to prevent dusting and spalling.

Concrete and Concrete Masonry: Unpainted concrete surfaces must be properly prepared in order to prevent poor adhesion of primers. Form oils and releasing agents need to be removed from the surface. Usually, a good washing with a detergent will remove the oils, releasing agents, dust and dirt.

Concrete sets in a short time, but the hardening or curing process continues for up to 96 days. When concrete is completely cured there is no longer active alkali on the surface which will cause paint to discolour, crack, peel and generally deteriorate.

Efflorescence is a white deposit which frequently appears in masonry surfaces. These deposits are soluble salts present in almost all masonry which have been leached out of the concrete by moisture. Primers will not adhere properly over efflorescence.

Efflorescence can be removed by washing concrete with a commercial solution of muriatic (hydrochloric) acid. The normal cleaning strength is achieved by taking 3 or 4 quarts of water and adding a quart of muriatic acid to the water (CAUTION: Always add the acid to the water - NEVER the reverse!!!). Follow the acid wash with a clear water rinse.

CAUTION: Muriatic Acid (Hydrochloric Acid) will cause severe eye and skin burns. Use in well ventilated areas. Wear appropriate protective equipment leg. safety goggles, neoprene rubber gloves and boots). Consult supplier's material safety data sheet.

Concrete Floors: Concrete that is hard and smooth should be etched so that paint can "grip" the surface. The etching may be done by using a solution of one part muriatic acid to eight parts water. Use a wooden or plastic bucket and apply with a stiff fibre brush. Allow solution to remain on the surface until bubbling stops. Then rinse with ammonia water followed by clear water. New floors should age at least three months before painting. Use Pratt & Lambert's Withstand Latex Floor Paint for basements or other concrete floors subject to contact with wet earth.

Sandblasting: On masonry surfaces where the cracking and scaling is extensive and adhesion of the paint to the surface is poor, sandblasting is often the only proper way to prepare the surface for the new paint.