Things You'll Need
Trisodium phosphate (TSP)
White oil-based or latex paint
Wood window sills add classic style to any room, but if you want a clean, sleek, modern look, you might want to paint traditional wood window sills white. Painting wood surfaces requires a bit of sanding and some specialized primer. However, once you've done the prep-work, painting the sill white is no more difficult than painting any other home surface.
Clean the window sill with a trisodium phosphate (TSP) cleaning product and a rag. TSP-based cleaners cut through the grime and oil that accumulate near window sill surfaces.
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Sand the wooden sill with 220-grit sandpaper. This will remove any glossy finish that has been placed over the wood's surface.
Wipe away the sanding dust with a moist rag.
Use painter's tape to protect the nearby window frame. If you're planning on painting the entire window frame white, then you don't need to section off the rest of the frame from the sill.
Apply a stain-blocking primer to the wood window sill using a paintbrush. Natural wood oils and artificial wood stains can seep through normal primer, and this will be especially noticeable with a white finish. Stain-blocking primer is ideal for long-lasting results.
Paint the sill with a white oil-based or latex paint after the primer has dried.
Apply a second coat of white paint if necessary after the first coat dries.
Remove the painter's tape once the final coat has dried for 24 hours.