ᐅ Paint on doors and windows changing from brown to purple

We replaced the wooden windows in our house between 1971 and 1983. They were repainted or glazed every few years. The last coat of paint, applied in 2014 with a high-quality window paint RAL 8016, according to the invoice, changed its color to purple within just 2 years, more or less strongly depending on direct sunlight exposure.

What puzzles me is the fact that the previous coatings between the original condition in 1971 and 1983—so for 43 and 31 years respectively—did not show any color change, only some fading at most.

To avoid making the same mistakes again, I would like to know what the problem is—wrong type of paint?

The picture shows a door facing southeast with different colors, covered and uncovered.

pinselquäler schrieb:

We replaced the wooden windows in our house between 1971 and 1983. Every few years, they were repainted or treated with glaze.
The last coat was applied in 2014 using a high-quality window paint in RAL 8016, according to the invoice. However, after only two years, the color started to shift towards purple, more or less strongly when exposed to direct sunlight.
What puzzles me is the fact that from the original condition in 1971 and 1983, after 43 and 31 years respectively, there was no color change aside from some fading.
To avoid making the same mistake again, I would like to know what went wrong. Was it the wrong paint?

The photo shows a door facing southeast with different colors on shaded and unshaded areas.

I would like to point out once again the areas where the varnish has faded and taken on a different color compared to the part with the original color. Could it be that the paint does not have UV protection?

Brown turns purple when the pigments used in the paint were too cheap. Red is generally one of the most unstable pigments, which doesn’t necessarily mean the paint was low quality. I often saw this on timber beams. It’s also common to see red cars fade faster. Solution: use brown mineral pigments in the paint instead of mixed synthetic browns.

Best regards
Gabriele

Is it possible to test the paint after 6 years to perform an analysis?