When inexperienced painters try to add latex and acrylic finishes over the top of existing oil-based paint, peeling often results. Oil-based finishes are not compatible with latex and acrylic paint because the latter has a water base. Most everyone knows that water and oil don't mix. To add latex or acrylic paint to a surface already finished with oil paint, apply a special type of undercoating formulated for compatibility with both oil- and water-based paints.
Instructions
1. Wear a dust mask. Lightly scour the existing oil-based finish to enhance its adhesive qualities. Use fine 150-grit sandpaper that won't carve noticeable flaws into the finish. Stop sanding once the existing finish feels slightly roughened.
2. Wipe down the existing oil-based finish using a rag dampened with mineral spirits. Let the solvent dry for 20 minutes.
3. Coat the oil-based finish with a shellac primer, using a 2-to-4-inch natural-bristled paintbrush. Apply gentle pressure as you brush to encourage attractive results. Carefully survey the primer undercoat and smooth any noticeable flaws before they begin to dry. Let the shellac base dry for two hours.
4. Wash the brush's bristles using alcohol.
5. Paint the existing oil-based finish as you primed it. Add a water-based latex or acrylic paint, using a 2-to-4-inch polyester paintbrush.
