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Paint on exterior masonry window sill blackening

Postby humble_prophet » Mon Apr 26, 2021 8:55 pm

Hi. The outside of my property was painted fairly recently; everything was OK except that a few days later, the white paint on the masonry windowsills started to blacken and darken, and gradually the paint started peeling. I'm wondering if anyone has experienced a similar issue and knows what causes it or has any solutions to suggest? Thanks.
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Postby stoneyboy » Tue Apr 27, 2021 9:36 pm

Hi humble-prophet
Most likely cause is that the sill has been painted with black bitumastic paint in the past. It is doubtful you will ever get rid of the BP but scrape back and see if you find a black layer of paint.
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