Film integrity and possible loss of adhesion may occur. Due to these possible conditions, most coating manufacturers approach fresh cementitious substrates with caution. In general, it is recommended that these substrates cure for 30 to 60 days or until a surface pH of 10 is realized. During this curing process, alkaline components generally are neutralized or leached out. In addition to hydrolysis, another failure encountered with premature painting is efflorescence.
Efflorescence is a white deposit of calcium and magnesium salts which migrate from the substrate.
It is often interpreted as an alkali-induced color fade. As always, care should be taken when working with acid. As a general rule, fresh masonry substrates should be permitted to cure to a pH of 10 or lower. The surface must be wetted with water prior to testing. Cure time for stucco to a level of 10 or less varies somewhat with prevalent weather conditions, but experience has shown that typically a cure time of 20-30 days will produce a substrate with an alkalinity reading of 10 or less.