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Experts Blame Salt for Powder on Stucco Coats

September 14, 1986

A white substance has appeared at construction sites all over San Diego, resulting in experts rushing to their laboratories to develop a defense against the powdery, crystalline material.

Despite its superficial similarity to a well-known illicit drug, the problem isn't a police matter: It's the presence of "efflorescence" on the sides of stucco and masonry buildings, according to Jan C. Winn, stucco products division manager for Expo Industries, San Diego.

"Stucco is not the problem," he explained. "Efflorescence is a predominantly winter season phenomenon that occurs when dissolved salts in plaster are leached out to the surface. The salts show as a white deposit after the water which carried them to the surface evaporates. Efflorescence is dependent upon water moving through the wall to reside on the surface."

Expo Industries, along with other firms, is researching ways to prevent efflorescence. Meanwhile, ways of reducing it is to always use clean, well-washed sand, use only clean mix water and use a low water-to-cement ratio to prevent the formation of salt deposits. Existing efflorescence may be removed by dry brushing and flushing with water.

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