Also, referred to as poster color, tempera paint is a permanent, quick-drying coating, consisting of pigment and a glutinous binding agent, like egg yolk. When Tempera peels from plastic, the culprit is almost always improper surface preparation. Because plastic is nonporous, it is ill-suited for any type of paint adhesion. Plastic surfaces should be abraded with sandpaper to provide a tooth for the tempera to adhere to. Properly conditioned plastic will maintain its tempera finish. However, for extra durability, you may want to apply a paint sealer.
Things You'll Need
Heavy-duty fabric drop cloth
Acrylic latex primer
2- to 4-inch latex paintbrush
Clean the plastic surface with dish soap using a coarse sponge. Rinse the soap from the plastic with wet rags. Dry the plastic with towels.
Stimulate surface adhesion by abrading the plastic with 220-grit sandpaper. Scour the surface until it feels gritty.
Wipe down the abraded plastic with a sticky tack cloth.
Place a fabric drop cloth beneath the plastic.
Coat the abraded plastic with an acrylic latex primer, using a 2- to 4-inch paintbrush, manufactured specifically for use with water-based latex paints. Wait two hours for the primed plastic to dry.
Wash the brush with water.
Coat the primed plastic with tempera paint using the cleaned paintbrush. Wait four hours for the finished plastic to dry.
If the tempera-coated plastic is located outdoors, apply a coat of protective paint sealer, using the latex paintbrush, to provide extra durability in varying weather conditions.
Never apply primer over non-abraded plastic, or the finish will peel.
Do not apply tempura paint over unprimed plastic, or it will eventually flake off.