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amyminge71

Chemical Reaction: Paint Changes Color on Stucco: Please help!

amyminge71
8 years ago

This is really bizarre, but when I apply paint to my home’s
exterior (currently white), it radically changes color. I have purchased over
40 samples. The grays change to bright purple. The whites change to almost neon
yellow-greenish white. Beige becomes orange. Multiple coats do not fix the
problem. Whatever substance is reacting with the first coat must go right
through to the 2nd, 3rd, 4th coats, etc. However, very dark colors do not seem to
change (or if they do, I can’t see the change).

(In case you’re wondering whether it’s simply a matter of perception, I have painted the wood next to the stucco, and the paint on the wood appears exactly as it should. The paint only changes color on the stucco.)

Apparently a chemical
reaction is occurring, but I don't know what it is, or how to remedy it.

Possible 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 not be a factor, but perhaps it is.

2-The previous owner told me that, around fifteen years ago,
he painted the house with "pool paint." (Yes, I know it’s bizarre.
Unfortunately, I don’t know what type of “pool paint” was applied, or why it
was applied.) In any case, this would be the most recent coat, which happens to
be white.

Chemistry Issues:

In the case of the grays, I don't know whether the grays
that turn bright purple already have some purple in them, & the reaction
with the existing wall is simply making the purple more intense,

OR

perhaps some gray pigments are reacting to actually become
purple.

OR

perhaps some pigments are being subdued or becoming
transparent.

The same questions apply for each of the samples. I just
used the grays as an example. I have some chemistry in my own background, but I am really
stumped by this problem.

Any help you give me would be very much appreciated! Thank you!

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