Alkalinity of stucco
Definition
The high pH of portland-cement stucco while it cures. Fresh stucco runs around pH 12.5 to 13 and drops as it cures over roughly 28 days.
Why It Matters
Coatings applied to stucco that is still highly alkaline can saponify, discolour or lose adhesion. This is why new stucco and fresh patches wait about four weeks, why an alkali-resistant masonry primer goes under the finish, and why a 100 percent acrylic finish is preferred over oil on stucco.
Simple Example
A new patch on a Dayton Valley house is scheduled for painting a month after the stucco contractor leaves, not the same week.