If you want to refinish your kitchen cabinets with a stain and clear finish, you have to strip them first, but you can paint over any type of finish without stripping, and sometimes that's your only option. Painting doesn't have to be a worse option; you can use glaze to turn painted cabinets into virtual works of art. Prepare the cabinets before painting by cleaning and etching the old finish with detergent and scuffing with sandpaper.
Get the Cabinets Ready
It's best to clean out the cabinets before painting, because paint has a way of splattering, even when you're careful. Doors should be taken down and all hardware should be removed; this may seem like an extra task, but you'll more than make up the time you spend doing it by avoiding the necessity to mask it or paint around it. You may not want to turn your kitchen into a workshop for the duration of the project, so bring the doors to a separate room and lay them out along the walls.
Cleaning and Scuffing
Cabinets will need to be cleaned with a detergent strong enough to remove grease and grime as well as etch the finish to provide a "tooth" for the new finish. Mix 1/2 cup of trisodium phosphate in a gallon of warm water and wash the areas you plan to paint thoroughly; then rinse with clear water and let the surfaces dry. Fill nicks and gouges with epoxy wood filler and sand the filler flat with 120-grit sandpaper. After that, scuff the cabinets lightly with 220-grit sandpaper. You're not sanding the wood; instead, you are merely roughing up the old finish to increase its tooth and ensure adhesion of the finish. Wipe the cabinets with a damp cloth to remove dust before painting.
Painting the Base Coat
If the cabinets have an existing oil-based finish, and you want to paint with latex paint, you need to prime first with an alkyd or 100 percent latex primer. Use a shellac-based stain-blocking primer if the cabinets are heavily stained or smoke-damaged. Apply at least two top coats, using latex enamel and a synthetic-bristle brush. You'll probably want to avoid oil-based enamels; they have higher levels of VOCs and are illegal in some states, such as California. Paint with even strokes, beginning at the top of each surface and working your way down. Finish each stroke on fresh paint -- a procedure known as painting toward the wet edge.
Glazing and Clear-Coating
After the base coat has cured for two or three days, you can add effects by glazing, which means to apply a thin coat of a paint of another color and wipe strategically to create shading effects. Gel stain can be used for this; it is easy to use and produces wood-tone effects that add antique nuances. Whether or not you glaze, the finish should be protected by applying at least one coat of water-based polyurethane. If you apply two coats, scuff the first one with 220-grit sandpaper before you apply the next coat to ensure the smoothest topcoat.