Painting a Lexan Body: Inside Out, and in Reverse

An RC body is clear polycarbonate — usually called Lexan, which is a brand name that stuck — and it is painted on the inside. Everything about painting one follows from that single fact, and almost every beginner mistake comes from not knowing it.

Paint on the inside means the plastic itself is the gloss coat. The finish is protected from stone chips, scrubbing and UV by a hard clear layer, and it stays glossy long after a painted-on-the-outside finish would be scratched dull. It also means you build the paint up in reverse, which is the part that catches people out.

The one rule that reorders everything

What you spray FIRST is what shows from the outside.

Think of it as looking through a window at layers stacked behind the glass. The layer closest to the plastic is the one you see. So the order is the opposite of every other kind of painting:

1. Details and small graphics first — flames, numbers, stripes, the small stuff.
2. Then the main colors.
3. Then a backing coat to make everything opaque and bright.

Get this backwards and your carefully masked racing stripe ends up buried behind the base color, invisible from outside, and there is no fixing it without stripping the whole body.

⚠️ Use polycarbonate paint. Nothing else.

Ordinary spray paint — enamel, lacquer, automotive rattle can — is the fastest way to ruin a body. Depending on the solvent it will either craze the polycarbonate into a web of fine cracks, or dry into a rigid film that flakes off in sheets the first time the body flexes.

Polycarbonate bodies flex constantly. The paint has to flex with them, and it has to use solvents that do not attack the plastic. Paint sold for polycarbonate — often labeled for "Lexan" or "R/C bodies", and commonly sold with a "PS" designation — is formulated for exactly that.

Airbrush users have their own polycarbonate-safe ranges. Same rule: check the label says polycarbonate, every time.

Safety: spray outdoors or in real ventilation, wear a respirator rated for organic vapors, and keep it away from ignition sources. There is a separate workshop fire safety guide on this site.

Preparation, which is most of the job

1. Leave the outer film ON

Bodies ship with a protective film on the outside. Leave it there for the entire process — painting, trimming, drilling, handling. It is what stops you scratching the surface you are trying to protect. It comes off at the very end, and peeling it is the best moment in the hobby.

2. Wash the inside

The inside carries mold release agent from manufacturing. Paint will not stick to it, and the failure shows up later as peeling or fisheyes.

• Warm water and ordinary dish soap.
• Work it over the whole inside surface with your fingers or a soft cloth.
• Rinse thoroughly, then dry completely — warm air, or leave it.
• ⛔ No solvents, no alcohol, no abrasives. They attack the plastic. Soap and water is the correct answer, not the lazy one.

After washing, do not touch the inside with bare fingers. Skin oil is the second most common cause of paint that will not stick.

3. Window masks

Most bodies come with pre-cut window masks. Apply them to the inside, over the window openings, before any paint goes on. Press the edges down properly.

If yours did not come with masks, cut your own from masking tape or use liquid mask. The windows are the part everyone notices, and a wobbly mask line is the difference between a body that looks made and one that looks painted.

4. Masking for multiple colors

• Burnish every tape edge down hard with a fingernail or a plastic tool. Paint creeps under any edge that is not fully stuck, and it creeps a long way.
• Work out your color order before you start — remember it is reversed.
• Liquid mask is worth learning for curved and complex shapes; it brushes on, dries to a peelable film, and follows compound curves that tape will not.

Spraying

Thin coats. More of them than you think.

• Shake the can properly — a full two minutes, not two shakes.
• Warm the can slightly if the room is cold; cold paint atomizes badly and spits.
• Hold roughly 6–8 inches away, keep the can moving, and start and stop the pass off the body.
• Several light coats, letting each flash off, beats one heavy coat every single time. Heavy coats run, pool in corners, and take days to cure.
• Work in a warm, dry space. High humidity can cause blushing — a cloudy haze in the finish.
• Between colors, let it cure properly before masking on top. Masking over soft paint lifts it.

A run on the inside cannot be sanded out, because the surface you are looking at is the plastic. This is the reason for the patience: on a Lexan body there is no polishing out a mistake.

The backing coat, and why colors look weak without it

Spray a bright color onto clear plastic and hold it up: it looks thin and washed out, because you are seeing light straight through it.

The backing coat fixes that. After all your colors are down:

• White or silver over everything — this reflects light back through the color coats and makes them look rich and solid. Silver gives a slightly metallic depth; white gives the truest color.
• Then black over the whole lot if you want to block light completely and stop the chassis and electronics showing through in bright sun.

Skipping the backing coat is the single most common reason a home-painted body looks weaker than a factory one.

Trimming and holes

• Curved lexan scissors cut the wheel arches and bottom edge cleanly. Ordinary scissors crack the plastic and leave a jagged edge that becomes a split.
• Cut slightly outside the molded line, then trim back. You can always remove more.
• A body reamer for body-post holes. It cuts a clean round hole and lets you sneak up on the size.
• ⛔ A twist drill grabs polycarbonate and can crack the body or snatch it out of your hand. If you must use one, run it in reverse to scrape rather than cut, and go slowly.
• Any sharp corner is a crack waiting to start. Round the corners of every cut-out, and if a crack does start, drill a tiny hole at the end of it to stop it traveling.

When it goes wrong

Finishing

1. Fit the body posts and check the fit before peeling anything.
2. Add decals to the outside — they are meant to go on the clear surface.
3. Peel the outer protective film last.
4. Let the paint cure fully before running. Fresh paint is soft, and the first bash will mark it.

Show it off

The Paint Shop on this site exists for exactly this — share the scheme, what you used, and what you would do differently. A finished body with the order of coats written down is worth far more to the next person than a photo on its own, because the order is the part nobody explains.

There is also a Show & Shine for finished builds, and the wider guides library if you want the mechanical side.

What this page still needs: photographs. Crazing, fisheyes and a proper backing coat are all things you recognize instantly once you have seen a picture and struggle to identify from a paragraph. If you have a body that went wrong, a clear photo of the failure would teach this better than the table above.