Painting Water-Stained Homasote Ceiling
At some point in the past, the plaster ceilings in my 1906 bungalow were covered with what appears to be 12" Homasote tiles. A few water leaks have caused dark brown stains, which I'd like to cover. All water leaks have been stopped (new roof), and some of the older stains have been painted over once but still show through. What's the best treatment? Cover stains with Killz several times and then paint the whole ceiling? Thanks for your tips.
Re: Painting Water-Stained Homasote Ceiling
best is to seal the stains with a pigmented shellac to prevent bleed through of the water stains. you can also use clear shellac and a highly pigmented primer overtop then paint.
depending on the condition of your ceiling tiles and remembering old homasote tiles can suck up a lot of paint, would suggest you first treat the spotted areas, then give the entire ceiling a top coat with the pigmented shellac first before you paint.
you can get a spray can of highly pigmented shellac from zinser or a can of BIN and roll or brush it on.
note: you might need to lightly sand the cured glossy surface of the shellac before you prime or paint to reduce the sheen that may come through and so your paint or primer will bond.