Guide To Painting Plastic
Plastic can be much more difficult to paint than wood, concrete, or other surfaces. Plastic is a smooth and non-porous surface, while substances such as wood and concrete have natural pores which effectively absorb paint. This means that paint often sticks poorly to plastic, as none of it is absorbed by the plastic, leaving it with a weak grip on the surface.
This is why painted plastic objects often flake, leaving unsightly, patchy finishes. With appropriate preparation, however, it is possible to paint plastic more successfully, and here at Best of Machinery we’ve put together some helpful tips on how to paint plastic to help you get the best and strongest coverage you possibly can when painting plastic.
Which Plastic Items Can I Paint?
There are many different types of plastic, and all of them will hold the paint to different extents. If you prepare your plastic surface appropriately and use the right type of paint, you can significantly improve the chances of getting paint to stick to most plastic surfaces, but there are a few types of plastic that are not appropriate for painting.
These include baths and shower stalls, kitchen countertops, and plastic floors. None of these will hold paint well, and several pose health risks if coated with flaky paint. Most other types of plastic should be appropriate for painting, however.
Preparing the Plastic Surface for Paint
Begin by cleaning the plastic surface you’re trying to paint. Use dish soap and warm water for this, removing any traces of dirt or grease from the item’s surface. Rinse any traces of soap from the surface with fresh water, and then carefully dry it off, ensuring that it’s completely dry before you continue.
Then, sand the surface lightly with fine sandpaper of 220 to 300 grit level. This adds a little texture to the smooth surface, enabling paint to stick to the plastic far better. It’s an important step and can make an enormous amount of difference.
As a final step, wipe the plastic down with a soft cloth dipped in rubbing alcohol.
This will remove any remaining traces of oil from the surface, helping to give the paint the best chance of sticking. Do this stage and all subsequent ones while wearing gloves, if possible, as oils from your skin can prevent paint from sticking properly to plastic surfaces.
Most types of paint won’t stick to plastic on their own and will require a coat of primer to be applied first in order to create a surface that the paint can stick to properly. Spray on primers are generally the easiest to use and provide the smoothest, strongest priming surface, but brush on primers also work well.
Whichever you choose, make sure you let the primer dry completely before you begin painting. Priming is an important part of painting plastic or other non-porous surfaces, as it makes a significant difference to the ability of paint to stick to smooth and non-absorbent surfaces.
Preparing the Paint
Before you start painting, make sure that the paint you’ve chosen is appropriate. Spray paints usually stick relatively well to plastic, with enamel and acrylic model paints coming in a close second. If the label states that it’s appropriate for plastic, you’re good to go!
If you’re using spray paint, shake the can for a full two minutes before you begin to spray. This may seem like a long time, but it’s a worthwhile step, as it ensures that the paint is fully mixed, giving you a smoother and more adhesive paint. Acrylic paints are safe to apply straight out of the tin, but if you’re looking to get a smooth surface, it’s worth thinning the paint with a little water.
This reduces the appearance of brush strokes, giving a smoother and cleaner final surface. Enamels may also require thinning, but cannot be thinned with water. For these, you should use a specialist enamel paint thinner.
Painting Plastic Surfaces
Some aspects of painting plastic are shared between different types of paint, while others are specific to each painting. We’ll cover the general rules first. Apply a thin coat first. Don’t worry if it doesn’t seem to be covering particularly well; you’re going to be following it up with more layers later no matter what type of paint you’re using. Once this coat is finished, leave it to dry fully before applying the next coat.
Brush or spray in the opposite direction for the second coat; if you’ve applied the first coat with vertical movements, switch to horizontal movements for this one. If, after the second coat is dry, you feel that the coating is not smooth or covering enough, apply a third and final coat. This one will need longer to dry. Leave it a full 24 hours before applying any kind of sealant!
If you’re spraying your coats on, hold the spray can 12 to 18 inches from the surface of the plastic and apply the paint in a smooth, sweeping motion. If you’re using a brush, make sure it’s a soft brush and apply the paint with care in long motions.
Sealing Painted Plastic
As a final step, a coat of polyurethane sealant varnish is a worthwhile feature. A few light coats of spray on polyurethane varnish, if allowed to dry for 30 minutes in between applications, will give a durable surface that’s resistant to the cracking and damage that plagues painted plastic surfaces.
If you follow our tips above, you’ll get the best and most durable finish possible on your painted plastic. Depending on the type of plastic you’re painting, it may still flake to some extent, but this is unavoidable. The tips above will help you to cover a plastic object to the maximum level possible for that particular type of plastic, giving the strongest surface possible. No plastic painting method is perfect, but these tips will help.