Paint Changes Color on Stucco. Chemical Reaction is Occurring, but What is Reacting?
PROBLEM: When I apply paint to my home’s exterior stucco(currently white), the paint changes color. The grays change to purple. The whites change to yellow. Greenish-beige becomes orange. I have purchased many samples of paint, and a color change is apparent for all but the darkest colors. The change in color starts happening immediately when I apply the paint, and it becomes more intense over subsequent days. 542
After a few days, there is a radical difference between the paint’s intended color and the new color.
Apparently a chemical reaction is occurring between the paint and a substance in/on the wall, but I don't know what it is, or how to remedy it.
SURFACE FACTORS: 1-The house is stucco, so perhaps the surface is very alkaline. The house was built in 1971, and several coats of paint have been applied by the previous owners since then, so I would think the alkalinity would no longer be a factor, but perhaps it is. (Would it even be possible for improperly cured stucco to remain highly alkaline for 44 years?)
2-The previous owner told me that, around fifteen years ago, he painted the house with "pool paint." (Unfortunately, I don’t know what type of “pool paint” was applied, or why it was applied.) My guess is that this was in response to the color-changing problem rather than the cause of the problem, but I don’t know for certain. (It is interesting that the pool paint has remained white all this time, while I’m unable to get a true white.)
PERCEPTION: In case you’re wondering whether it’s simply a matter of perception, I have painted the wood that is immediately next to the stucco, and the paint on the wood appears exactly as it should and it remains constant in color over time (aside from becoming just slightly lighter as it dries). In other words, the paint only changes color on the stucco. Since the wood was never painted with pool paint, and since the wood is obviously not stucco, I still don’t know which factor (pool paint, stucco, or something else) is causing the color change. However, this does show me that it’s not an issue of perception, lighting or viewing angle. The paint color is truly changing on the stucco.
I have some chemistry in my own background, but I am really stumped by this problem.
Any help in figuring-out what’s going on would be very much appreciated. 414