Because vinyl has a slick, smooth texture, there are certain preparation techniques that must be performed before it can be painted. Many do-it-yourselfers skip these critical steps either because of impatience or ignorance. Often, this results in a finish that chips and peels over time. If you plan to paint vinyl signs, you need to pay special attention to preparation, or you're likely to end up with disappointing results.
Use soap and water to clean the surface of the vinyl signs. Rinse the vinyl signs thoroughly before you continue.
Remove the glossy surface layer with TSP(trisodium phosphate)-water mixture. Read the label, and follow the manufacturer's application instructions exactly. Allow the vinyl signs to dry completely before continuing.
Score the surface of the vinyl signs with 80- to 120-grit sandpaper to promote adhesion. Sand in a circular, counter-clockwise motion.
Apply blue painter's tape to any areas you do not want painted.
Fill the painter's pail or 5-gallon bucket about halfway with latex primer.
Use the 3- to 4-inch paintbrush to apply primer to the vinyl signs. Be especially careful to smooth any runs or drips as you apply the primer.
Wash the 3- to 4-inch paintbrush and painter's pail or 5-gallon bucket with water. Use your fingers to work the water into the bristles of the paintbrush. Shake the brush vigorously to remove excess water.
Repeat Steps 5 and 6, except use exterior acrylic latex paint instead of latex primer.
If the vinyl signs have mould on them, use a mixture with a ratio of one part bleach-to-16 parts water to kill it before you apply primer. Otherwise, the mould will bleed through. Choose an exterior acrylic latex paint containing urethane, to ensure good adhesion and durability.
Never attempt to paint vinyl signs without scoring them with sandpaper first to promote adhesion. Never attempt to paint vinyl signs without priming them first, or you will end up with chipping and peeling.