Plastic is non-porous, so painting it is harder. But since chalk paint has super adhesive qualities, can you use it on plastic?
You can use chalk paint on plastic. But, you must clean and sand the surface first. Sanding will create tiny scratches that the paint can penetrate into.
However, if the plastic is already painted or sealed, you must remove the existing finish first. That’s because paint doesn’t stick over a sealed surface.
Chalk Paint Dry Time on Plastic
It takes chalk paint 15 minutes to dry to touch, 30 minutes to dry enough for a re-coat, and 24 hours to fully dry (cure) on a plastic surface. To dry, the solvent (water) must evaporate from the coating. Since water evaporates fast, the paint also dries fast.
However, the dry time depends on the humidity levels, surface type, room temperature, and thickness of the coats. For instance, if the paint is applied over a dirty surface, it will take longer to dry.
Chalk paint dries faster on plastic surfaces than on any other surface. That’s because the plastic surface is non-porous, so the paint doesn’t penetrate its surface. This means the evaporation process (of the solvent) happens faster because all the paint is over the top layer of surface.
How To Apply Chalk Paint on Plastic?
You must prep the plastic properly before applying chalk paint. Chalk paint must penetrate (soak into) a surface to stick. But, since plastic is non-porous (doesn’t allow penetration), you must sand the plastic to create scratches that the paint can soak into.
Here’s how to do it:
1. Prep The Workspace
First, prep the workspace. Remove nearby objects and cover the floor with a drop sheet to prevent paint spills. Also, wear safety goggles.
2. Clean The Surface
Before painting, clean the plastic because its surface is riddled with dirt, grime, and dust that can prevent the paint from sticking.
To clean it:
- Mix warm water with soap or detergent.
- Apply the mixture to the surface.
- Use a soft brush to scrub the dirt.
- Wait 5 minutes.
- Rinse the plastic with clean water.
If you don’t clean it, the paint won’t stick and will peel off.
3. Remove Existing Finish (Optional)
If plastic is painted or sealed, you must remove the existing finish first. That’s because a sealer forms a glossy finish that prevents liquid from penetrating its surface, including paint. Also, if the existing paint is oil-based, you must remove it because chalk paint doesn’t stick over it.
To remove an existing finish:
- Apply a paint remover compound over the surface.
- Wait a few minutes.
- Use a plastic scraper to remove the paint.
- Re-apply the paint remover compound to leftover paints.
- Use a rag to remove the leftover paint.
- Rinse the surface with clean water.
If the surface isn’t painted or sealed, skip this step.
4. Sand The Plastic
After cleaning the plastic, wet-sand it. Sanding will remove imperfections from the surface and create tiny scratches that the paint can soak into.
To sand plastic, use fine-grit sandpaper. Fine-grit sandpaper won’t damage or create noticeable scratches. Avoid using coarse-grit sandpaper as it can damage the plastic. To prevent dust, wet-sand it instead of dry-sanding it.
After sanding, clean the surface.
Related Read: Can You Sand Chalk Paint?
5. Prep The Paint
New chalk paints don’t need to be prepped before use, but old paints do. So, if you have old paint, mix it (or stir) it before using it. If you don’t, the paint won’t have a consistent flow or color. Follow the manufacturer’s instructions to know how to prep it.
Also, if the paint is too thick, you must thin it because a thick coating won’t stick to a non-porous surface. To thin chalk paint, use a ratio of 4:1 (4 parts chalk paint, 1 part water).
6. Paint The Plastic
Once the plastic surface is clean and sanded, apply chalk paint.
To apply chalk paint over plastic:
- Use a paintbrush or sprayer.
- Apply 3 coats.
- Wait until one coat dries before applying the next one.
- Sand between coats (except the last coat).
- Wait for the last coat to dry fully (cure) before using the surface.
Optionally, you can seal the finish with spar varnish, polyurethane, or wax for outdoor plastic surfaces.
Related Read: Will Chalk Paint Stick To Glass?
Sealing Chalk Paint
You must seal chalk paint on outdoor plastic surfaces because the paint doesn’t have extra additives that make it durable enough to withstand outdoor elements.
If exposed to outdoor elements (rain), unsealed chalk paint won’t last more than 6 months because it has low water-resistant qualities. However, if you seal it, the finish will last up to 5 years.
A sealer will produce a clear coat over the coating and protect it from water, moisture, scratches, handling, and other damage. You use wax, spar varnish, polyurethane, or lacquer to seal chalk paint.
Types of Plastic Surfaces
You can use chalk paint on decorative plastic furniture. However, you shouldn’t use it for high-traffic furniture surfaces as the paint isn’t durable enough to withstand constant usage.
You can use chalk paint on indoor plastic plant pots because they aren’t exposed to constant water or usage, so the finish will last longer. However, for outdoor pots, you must seal the chalk paint with an exterior sealant such as polyurethane or spar varnish.
You can paint a plastic table with chalk paint, but you must seal the finish. That’s because tables are exposed to constant usage and water that can wash off the paint.
Also, they have a flat surface, so if water is spilled over them, the water won’t slide down. Instead, the water will stay on the table and penetrate the paint. So, sealing the finish is necessary.
You can paint plastic picture frames with chalk paint because they aren’t exposed to water, usage, or moisture. You also don’t have to seal the finish.
To apply it:
- Remove the picture.
- Clean and sand the frames.
- Apply 3 coats of chalk paint.
- Wait until the final coat dries before hanging the picture frame.
However, if the picture frame is exposed to a lot of usage or handling, seal it with wax.
You can use chalk paint over plastic, but you must prep the surface properly. Plastic is non-porous, so you must clean and sand it before painting it. For outdoor plastic surfaces, you must seal the finish because chalk paint isn’t durable enough to withstand outdoor elements.
Tony is a professional painter and an author of DIY Geeks. Tony has completed over 1,000 painting projects for his clients. It's safe to say he knows what he Is talking about,