Removing efflorescence from plaster

PART 1---GENERAL  1.01 SUMMARY       A.   This procedure includes guidance on removing           efflorescence from plaster surfaces.              1.   Efflorescence is a condition where white (salt)                deposits (in the form of a fluffy powder) form on                the plaster surface.  The formation of salts is                usually a sign of excessive amounts of moisture in                the back-up material, such as brick or concrete.              2.   Salt deposits on the surface may develop from                soluble compounds within the adjacent masonry or                in the soil.  In the presence of water, these                compounds gradually migrate to the wall surface,                where they remain when the water evaporates.            3.   These deposits are generally not harmful to the                material, just unattractive.  However, they should                be removed from the surface as soon as possible. 

PART 2---PRODUCTS  2.01 EQUIPMENT       A.   Clean sponge       B.   Stiff, fiber bristle brush   PART 3---EXECUTION  3.01 EXAMINATION       A.   Before proceeding with steps to remove efflorescence,           examine the plaster and substrate material for           potential sources of moisture and make repairs as           required:            1.   Determine the age of the structure:  Efflorescence                on older buildings is typically caused by the                presence of soluble salts in the construction                combined with moisture.            2.   Determine the location of the efflorescence:                 Examination may show where the water is entering.            3.   If possible, examine the condition of the back-up                material:                   a.   CAREFULLY EXAMINE the wall for open gaps or                     cracks in joints and around openings that                     could allow water to enter the building.                        1)   Are joints properly caulked or sealed?                        2)   Are flashings and drips in good                          condition?                      3)   Are there open or eroded mortar joints                          in copings or in sills?                 b.   Carefully note the condition and profile of                     the mortar joints.                 c.   Repair cracks in masonry and/or repoint as                     necessary before proceeding with the cleaning                     operations.            4.   Examine wall sections and details of construction:                 Carefully examine roof and wall junctures and                flashing details for possible sources of moisture                entry.            5.   Examine laboratory test reports on the materials:                 The problem may stem from the composition or                misuse of the material.  3.02 ERECTION, INSTALLATION, APPLICATION       A.   Carefully remove any surface deposits using a stiff           fiber bristle brush only.       B.   Wipe the surface with a clean, damp cloth.