I'm repainting an old plaster ceiling in my house. I took off the popcorn texture, scraped, and sanded everything, which exposed a large stain that looked like a water stain.
I soon discovered about 6 inches of bat poop (guano) directly above the stain in the attic by the chimney, so I removed that. So, the stain is either from the guano itself, or the chimney area happened to be conducive to both bats and water leakage.
Anyway, I painted the ceiling with water based primer, and applied a few coats to the stained area. Then I used white latex ceiling paint, and the stain still bled through.
I've read other posts that say to use oil-based primer to cover a stain, so my question now is; can I put oi-based primer over the latex primer and white latex ceiling paint? Or, do I have to sand back down to the plaster in order to apply the oil-based primer?