How to Paint Exterior Windows

Clean the windows to remove grime, dust and cobwebs. Use a mild detergent and a scrub brush, and rinse them well with a hose. Use a mixture of one part bleach to three parts water to remove mildew by spraying or brushing it on and waiting about five minutes before rinsing. Allow the wood to dry.

Scrape all loose paint with a chisel-edged paint scraper. When you can't remove any more paint, sand the window down with 80- or 100-grit sandpaper. A handheld electric palm sander will speed up the process on flat areas.

Remove old, loose caulking and glazing compound. Brush the dust and loose wood fibers out of the cracks and around the edge of the wood sash.

Prime all exposed wood with either acrylic or alkyd primer. Use alkyd primer over old oil-based paint or if the wood is very soft and punky. Allow the primer to dry as directed on the label.

Caulk or fill cracks, gaps and holes. Use paintable silicone caulking for gaps and cracks in the wood; exterior spackle for smaller holes; and wood putty or automotive body filler for large holes or damaged wood. Prime over spackle, putty or filler. Caulking does not need to be primed.

Glaze the window sash if you are painting older wood windows. Use a glazing tool or flexible one-inch putty knife to lay the glazing smoothly along the window glass. Purchase modern glazing compound that can be painted within a day or so; some of the old-style glazing compounds have to cure for about 30 days before being painted.

Paint the windows with two coats of acrylic latex paint. Paint from the inside out: first, the window sash, then the frames and finally the sill. For the most professional look, paint the returns, which are the edges of the trim to where it meets the siding.

Open and close the windows periodically for about 24 hours to make sure the paint doesn't stick. Do this whether you have double-hung sliding windows or cranking casement windows.