How to apply Lexan bodywork paint?

Here is a complete and detailed tutorial on the different steps, techniques and products used to paint a miniature bodywork with Lexan paint for RC modeling. The decoration and personalization of radio-controlled vehicle bodies is done from the inside of this very special transparent and shiny plastic called Lexan. The application of specific paints for Lexan is mainly done with an airbrush and in certain special cases with a brush. As the application is done on the inside of the Lexan, the order of the different stages of a conventional paint application is reversed. I invite you to watch a complete tutorial video at the end of this article.

Summary of steps
► Step 1: preparing the Lexan before painting
► Step 2: masking before painting
► Step 3: creating the decor
► Step 4: cutting
► Step 5: Airbrush Painting on the Lexan
► Step 6: final painting

How to Paint Lexan and bodywork Miniature Cars

Step 1 / Preparing the Lexan before painting

The first step in preparation before painting is to prepare the Lexan. The purpose of preparing the surface is to guarantee good performance of the Lexan paints. In the field of radio modeling, the bodies and their paints are subjected to severe tests, with tensions, shocks, or even high temperatures. It is therefore an essential step to which I always take maximum care.

I always start by sanding the interior of the Lexan bodywork. Like all plastics, it is not recommended to use sandpaper, but rather abrasive sponges. Among the different grains of abrasive sponges, I recommend the gray color which corresponds to a fine sanding grain. It is also possible to use the higher sanding grain with the green abrasive sponge. The abrasive sponge has the advantage of creating adhesion through micro-scratches, very easily even when the interior of the bodywork has complicated angles and reliefs.

Then, always to guarantee my client a maximum level of adhesion of the paint that I am going to apply, I practice meticulous degreasing of the surface. This removes all invisible contamination, for example fingerprints, traces of glue or plasticizers, silicones and other types of grease. I use heavy solvents like Gasoline C or Bodywork Paint Degreaser because I know they are very effective against silicones and glues and do not affect the transparency and strength of the Lexan. There are also very effective Hydro degreasers. In my experience, some painters even use lye and it gives very reliable results.

Step 2 / Masking before painting

In general, in the field of paint for radio modeling, it is not common to use adhesives, as is the case in the field of customization in motorcycle painting or on helmets. On Lexan, I don't use adhesive thin lines or tape, but rather liquid mask. Very clearly, I find that the liquid mask has the great advantage of being applicable very quickly and whatever the shape and angles of the bodywork.

For this, I use Liquid Mask Hikari: it is a slightly thick product, which must be applied in a thick layer, so for this I use a paint gun with a 1.4 mm nozzle. This liquid masking product can be perfectly applied with a small gun or even with an airbrush, as long as it is diluted to 10 or 20% with water. The liquid mask can be whitish, pinkish or even bluish, but it becomes transparent after drying. The liquid mask dries quite quickly and at a cool temperature of 20°C. I can start my drawings after about an hour.

I advise you, for this particular product, to apply a layer with sufficient thickness, because if the thickness is too thin, the dry film will break when you try to pull it. I use a pressure of around 3 to 3.5 bars and apply 2 or 3 even coats.

Step 3 / Creating the decor

For this step, there are no particular instructions, other than to let your creativity speak. I will still give you some tips, starting by using a marker with a fine tip. Plan to create colored lines with a thickness of 3 to 6 millimeters to demarcate the different color areas. For my part, I always try to visualize completely and in detail all the stages of the succession of colors. To do this, I take colors into account by applying (except of course lines) light or transparent colors first rather than dark colors. Once my action plan is verified and validated, I move on to the layout of the decor.

Concerning the symmetry of the design, I always start by making a line in the center of the Lexan bodywork and I create my decoration on one of the sides. I then trace with paper masking tape, which I transfer to the opposite side to the exterior of the bodywork. All I have to do is follow and draw the decoration with my fine tip marker inside on my dry liquid masking. I thus obtain a perfectly symmetrical decor.

Step 4 / Cutting

For this step I use a scalpel. I advise you to always use a new cutting scalpel. This way, you will have no problem when you remove the masking areas and a single pass of the scalpel will ensure you cut perfectly and without forcing. Be careful never to force it, because if you cut too deeply, you can weaken the bodywork. This is why I advise you to use a new blade before each cut.

Step 5 / Airbrush Painting on the Lexan

There are several ways to airbrush: I sometimes prefer to create a thin layer of adhesion, before applying one or two thicker layers. When I'm in a hurry, I apply the paint directly in 2 coats.

I usually use a hair dryer to speed up drying and to avoid runs. It is even possible and this is a tip that I really recommend, to blow dry the plastic or the liquid mask, or even any paint, just before applying a new coat of color, because it improves the adhesion and grip of the paint. Attention ! Don't overdo it with hot air, as it can crack the paint if you blow too close or too long to the paint.

For most radio model scenery, you start by painting the lines, which can be black, red, white or any other color depending on your project. This is the color that will appear first on the bodywork.

After each color, I successively and methodically remove the masking areas one by one while applying the colors.

Important ! I do not recommend letting the paints dry and harden for more than 12 hours before removing the masking, because if the paint film hardens, then you risk having problems with peeling. Generally, I remove the masking between when the paint has started to dry slightly but before it is completely dry, i.e. when it is "tacky".

The different CUSTOM effects with airbrush or others

There are many techniques for creating cool graphic effects on radio model racing bodies, I know some of them but not all!

For example, there are paint splashes with a brush, or even rapid brush strokes directly on the surface, which gives a “racing” style.

There are also many “flying stencil”* techniques or even marbling effects: I often use tow to spray through with my airbrush. For example, I apply black contrast color, first, through the threads and I move or strip my fiber to vary the patterns. Then, at the back, once the marbled decoration has been created, I usually apply an aluminum paint which gives maximum contrast with the black patterns.

Shading: this is a very well-known technique which consists of following the edge of the masking with a thin layer of black sprayed with the airbrush. In the case of a Lexan bodywork, the shading is done first, then followed by the color. This creates a sort of 3D depth or trompe-l'oeil effect that is very, very appreciable!

There is also the drop technique: I spray a few drops of water on the surface and I roll these drops by spraying a thin layer of black paint on the side with the airbrush. Here too, I then cover with aluminum paint and this gives a really very interesting drop effect.

There are many effects like this and we can always invent new ones! They allow you to vary with the monotony of paints or sprayed and too perfect gradients!

*A flying stencil is a stencil that is non-adhesive and is held manually on the surface. It can be moved or removed at any time.

How to follow the colors?

Some colors may migrate. This is the case with Candy paints, because they are not made of pigments, but rather of dyes and these products have the unfortunate tendency to migrate, that is to say to cross the layers, to reveal themselves even after drying . This manifests itself as a Candy color which bleeds a lighter color.

There is a product that exists to remedy this and which is called BLOCKER: it is a kind of varnish that is impermeable to Candy and which effectively prevents color migration.

In the reverse process of applying layers of color to a LEXAN bodywork, I also pay close attention to the covering power and natural transparency of certain shades. Some colors, like white or black, are perfectly opaque. However, there are semi-opaque or less covering colors! This is the case, for example, of certain yellows or certain reds.

As in the video shown below, it is prudent to apply a thin layer of white to ensure that other colors applied later will not alter the color in the foreground. I call this “backing”.

Advice: I advise you to avoid the accumulation of layers with the creation of large thicknesses above the liquid masking, because there comes a time when the superpositions of thickness and the hardening of the color become too great for the film of the Liquid mask can be removed easily, with a clean cut. However, this is logical and should be thought about at the painting planning stage.

Step 6 / The final painting

Once all areas are painted and all masking is removed, I usually apply a clear, opaque color coat to the entire bodywork. This color applied to the rear can be visible on certain areas of the bodywork seen from above, but its usefulness is more to create a homogeneous and opaque background which will allow all the colors to show their optimal appearance.

Of course, this white background is obligatory if I have previously used fluorescent paints or even very light pearlescent paints. It is always important to use the recommended background color for certain special effects (and in many cases, for example for chameleon paintings, it is necessary to use a black background).

Since the painted bodies are intended to be used in radio-controlled vehicle races using thermal engines, the colors are subject to exhaust fumes, sometimes significant heat and even gasoline splashes. To protect all my decor, I therefore use a layer of NITROBLOCK which is a product that is supposed to resist all types of fuel.

It is a white, opaque and thick product, which has an ammonia-like smell and which I apply with a spray gun. As the product can be diluted with water, it can be applied with an airbrush. However, to obtain a thick, protective layer, it is quicker to use a paint gun.

Last note: Lexan paints are products that ensure maximum flexibility even after drying and curing for several weeks or months. This prevents the paintwork from breaking when the bodywork is twisted. Flexibility does not mean fragility, because Lexan paints are very resistant.

One of the things I demand from my paints is, above all, impeccable adhesion to Lexan. The decorations that I create for clients are often the result of several hours or days of work and the paintings must be guaranteed. For this, I only use specific paints for Lexan!