I need to repair peeling flaking exterior paint on my stone window sill, so looking to find a suitable matching paint but I'm puzzled on what this stuff is.
Looking at the back of the paint, it looks like what feels like some sort of substrate is attached... feels like construction paper but if you look closely it is actually made of sand-like masonry. Does that mean there is some sort of masonry primer I should use when I'm painting this sill?
Or should I just scrape all the old paint and substrate off and just paint with a regular exterior paint?
What's the best way to remove this kind of stuff, I can scrape the flat surface with a putty knife to remove, but the vertical side has an irregular rough stone pattern - should I just sand it off there?
Wide-angle shot of the outdoor sills when they were just renovated in 2015