How to Paint on Plexiglass?

If you don’t know how to paint on plexiglass, you were most likely surprised when all the paint peeled off almost immediately once dried. Plexiglass is a tricky material to work with. It needs a good amount of preparation before any kind of paint will take to it.

In this article, you will learn about the processes to make the paint adhere to plexiglass, which is one of the most difficult materials to paint.

What to Prepare:

• Medium-grit sandpaper (anything from 80- to 150-grit will do)
• A sponge
• A bucket of soapy water
• 2 x polishing cloth
• Acrylic primer
• Acrylic paint (spray-on or paint-on)
• Brushes or rollers – The size will depend on the size of the surface to be painted.
• Masking tape (optional) – Use this to prevent paint from getting on the parts you don’t want to be painted.
• Plexiglass sheet
• Waterproofing sealant (optional)

Detailed Steps:

Step 1 – Sand the plexiglass

The first and most important step in how to paint on plexiglass is sanding the surface. This will provide the primer with a rough surface to adhere to. Painting on a smooth plexiglass surface without preparation will only cause the paint, both the primer and paint, to peel off once they dry.

Take a bit of medium-grit, I suggest 100-grit, sandpaper, and scuff up the surface of the plexiglass you will be painting. If you want certain parts to remain unpainted, cover them with masking tape. Using medium pressure, sand the surface of the plexiglass until it is no longer shiny.

Step 2 – Wash the plexiglass

You cannot start painting yet because plastic dust now covers the surface of the plexiglass. Painting over this surface now will make the final paint job uneven and bumpy, which means you have to start over.

Dip the sponge into the soapy water and proceed to scrub the surface of the plastic. Rinse the plexiglass using clean water and then completely dry it using a clean rag. For better results, let the surface dry for 1 or 2 hours. Never paint over a wet surface.

Step 3 – Apply the primer

Once the surface is clean and dry, you can apply the primer. The primer will give the paint an even and rough surface to adhere to. It would be much better than painting the bare surface. First, lay down a couple of sheets of newspaper to keep the floor clean and paint-free.

It is much easier to use a spray-on primer. It also provides a more even application. Hold the spray can 8 inches away from the plexiglass and angled at roughly 45-degrees. Start spraying away from the plexiglass and then spray across the surface. Use quick strokes and do not stay too long in one place.

Step 4 – Add another layer if needed

Sometimes, the surface of the plexiglass is not that even, so adding several coats of primer may be necessary. Before you spray on the next coat, you should let the first coat dry completely.

You don’t need to sand the first coat of primer as it is rough enough already. Before the primer dries completely, remove the masking tape. You might accidentally peel off the paint if you let it dry before removing the masking tape.

Step 5 – Paint over the primer

Before you continue painting, replace the masking tape you removed earlier. You can now proceed to spray the surface with your preferred color paint. Again, hold the paint can at least 8 inches away and at a 45-degree angle.

Just like how you did with the primer, spray across the plexiglass and apply light coats. However, if you will be doing multiple coats, let the first coat dry completely.

Also, you should sandpaper the surface lightly before applying the next coat. I suggest using 140-grit sandpaper for this step. After sanding, take a damp sponge and wipe over the scuffed surface to get rid of the dust.

Apply as many coats as you see fit. Remove the masking tape once the paint gets tacky, but still not completely dry.
What kind of paint can you use on plexiglass? Ideally, you should only use acrylic paints for plexiglass. Other paints, especially latex paints, tend to react with plastic, often melting the surface.

Step 6 – Apply waterproofing sealant (optional)

If you will be placing the painted plexiglass outside and exposed to the weather, you should apply 2 or 3 coats of waterproofing sealant over the dried paint. You can use either a matte or glossy sealant depending on the look you are going after.

How to Get Paint Off Plexiglass?

If you want to start over because, for some reason, you were not happy with the color of the paint, here’s how to get paint off plexiglass.

What to Prepare:

• 1 or 2 bottles of denatured alcohol (depending on the size of the Plexi)
• A bunch of rags
• Painted plexiglass surface

Detailed Steps:

Step 1 – Apply the denatured alcohol

Grab a rag and soak it with a bit of denatured alcohol. Proceed to rub the denatured alcohol over the painted surface one small section at a time. Put a liberal amount of denatured alcohol all over the painted surface and let it soak into the paint for 2 to 5 minutes.

Step 2 – Rub off the loosened paint

Once the paint softens enough, grab another clean rag soaked in denatured alcohol and proceed to wipe away the paint. The paint should be loose enough that you can take it off completely with ease.

Step 3 – Sand off any remaining bits of paint

The denatured alcohol usually does not remove 100% of the paint from the plexiglass surface. To get rid of all the remaining paint, sand it off using medium-grit sandpaper (I suggest 80-grit).

Step 4 – Clean the surface

Once you remove all the paint, wash the surface using some soapy water before repainting. This will remove the traces of the solvents you used prior. Not doing this will ruin any paint you put on the surface.

Step 5 – Polish the plexiglass

If your original purpose was to make the plexiglass clear again by stripping off the paint, you’ll be disappointed at how cloudy it will be. The solvents that you used to strip the paint will also cause the plexiglass to get cloudy.

However, you can polish it by wet-sanding using gradually finer sandpaper (from 180-grit to 220-grit). Finish it off by using some polishing compound. It might not still be quite as clear as you wanted, but it will be a huge improvement from what it was originally.

Helpful Tips

• Use acetone – You can also use acetone (CH3COCH3) to strip the paint off a plexiglass surface. However, I suggest doing this carefully as acetone is a strong solvent. It might soften or even melt the plexiglass if it is not that thick.
• Never use latex paint on plexiglass – Latex paint contains solvents, like paint thinner, that will destroy plexiglass and other kinds of plastics.

Quick Guide to Sandpaper Grit Sizes

Conclusion

Although plexiglass and other plastics are difficult to paint, as long as you know how to paint on plexiglass properly, it will not be quite as hard. It will take a lot of preparation, and a whole bunch of effort and patience, but it will be worth it in the end.

If you follow the guide above and avoid using paints that are not compatible with plexiglass, your next project may turn out better than you first expected.