How to Avoid “Orange Peel” When Painting Gunpla

Painting Gunpla kits with an airbrush can give them extra oomph. But for all the benefits that come with these techniques, there are downsides to watch out for, too. Join Megaplamo as he explains the how and why of avoiding the dreaded “orange peel” paint texture. 

Gunpla is freedom. You can do whatever you want. However, sometimes it is good to know the rules before you break them. We’ve all made a mistake and then called it “weathering.” By knowing the best practices, you can customize Gunpla on purpose instead of by accident. 

When you start airbrushing, one of the first challenges you will have is achieving a good finish and that means avoiding an unpleasant paint result known as “orange peel.”

What is orange peel? You know how the skin of an orange has a porous, uneven surface? Even though it’s all the same color you can see its mottled texture. It may look fine on a fruit, but it isn’t something you would want on a plastic model. Orange peel is difficult to photograph, but you can see it in the reflective areas of the painted spoon below:

The best way to avoid orange peel is to get the right airbrush setup before you start painting. That will vary based on the type of paint you are using.

The three things to keep in mind are:

• The viscosity of your paint.
• PSI (air pressure) on your compressor.
• Type of paint you are using (water or solvent-based).
• Type of paint finish (matte/flat, satin/semi-gloss, or gloss). You can learn more about the basics of paint in our Paint Types 101 article. 

For this tutorial, I’ll be using semi-gloss paint with my Badger Patriot 105 airbrush. I will show you two examples: one of water-based paint and one of solvent-based paint. 

You will also need a:

• Pressure gauge 
• Moisture trap or water-trap filter
• Vallejo airbrush paint thinner*
• Vallejo paint flow-improver*

*Or a similar product from the brand you prefer. These are the products I used. 

How to Avoid Orange Peel with Water-Based Paint

If you are using water-based paint such as Vallejo, Citadel, or Army Painter, you will need to raise the pressure to 30 PSI (around 2.06 Bar). This is because the paint has a high viscosity and in order to properly atomize it, you’ll need more pressure. Use two drops of thinner and two drops of flow improver per 10 drops of paint. This will slow the drying time and allow the pigments to settle and dry smoothly.

I used Vallejo’s thinner and flow improver for water-based paints because it works with the brands that I mentioned above. Note that some water-based paints claim you can put them directly into the airbrush cup without thinning. Although this is true, you will have a difficult time dealing with the paint clogging your brush and the result won’t be as smooth.

The best practice for a smooth, even finish is to go slow. No, even more slowly than that! In my photos, you’ll notice that my first coat barely even changes the color of the spoon.

Continue building up the layers one at a time, pausing for a few seconds in between each round. You will notice that the pigments are spraying very finely and as you build the layers the end result is a very fine satin finish. For this example, I used Vallejo Electric Blue.

Now here’s an example of what NOT to do. If you spray water-based paint at lower pressures than recommended, and without thinner and flow improver, it will cause the paint to splatter and build up a dimpled texture that you don’t want.

You can see that with low pressure the paint is coming out uneven, and you see some speckling. As you continue, it just gets worse, and then results in the orange peel texture.

Another issue to watch out for with water-based paint: it tends to dry on the tip of the needle, causing paint to spray unevenly. Check the airbrush tip often, and keep a cotton bud soaked in thinner on hand. Gently wipe the needle when it happens. You’ll find that this isn’t as much of an issue with solvent-based paint.

How to Avoid Orange Peel with Solvent-Based Paint

When using solvent-based paint such as Mr Color or Tamiya, you will want to lower the pressure to 15 psi (Around 1.03 Bar) and add a lacquer leveling thinner. Tamiya lacquer thinner works well but Mr Color Leveling Thinner is golden if you can get ahold of it.

Although Tamiya is considered to be acrylic, it is also solvent-based which causes a lot of confusion. The pigments are acrylic and the base is an alcohol solvent. That’s why Tamiya sells both acrylic and lacquer solvents for their paint, and why you can use Mr Leveling Thinner with Tamiya. Water actually breaks down Tamiya paint—making for easy clean-up, but serious issues if you use water to thin it in the airbrush.

For this example I will use Mr Color Gundam Color “Char’s Red.”

Go slow and build up your paint in multiple layers. Since lacquers have a lower viscosity than water-based paints, you won’t need as much pressure to atomize it.

Notice how fine the pigments look as I spray. Your final satin finish should look similar to the spoon in the picture on the right.

Keep in mind that too much pressure (>20psi) will cause it to come out grainy and have a sand like texture, similar to orange peel and equally undesirable!

Both of these examples use satin or semi-gloss paint. When it comes to gloss paint, you will want to do things slightly differently. You will still use thinner, but start with a mist coat—a light, airy, coat that looks misty like the name—and finish with a wet coat—a thicker coat that looks shiny and damp as it goes on, but not so thick that the paint drips and pools. For matte paint, use several mist coats, then several semi-wet coats. 

Whichever type of paint you are using, here’s some universal advice: don’t stay in one place too long and be sure to move to a different location once you see light reflecting from the surface. It’s a lot to remember, but practice makes perfect. It helps to experiment with just how much paint and pressure you will need to achieve these varying coats!

Below is an example of a gloss coat. You can actually take it even further than this using a polishing compound, but that is a subject better suited for a different tutorial.

Here is a matte-finish paint coat:

If you make a mistake, you have two options: you can either strip the paint and start over, or you can “hide your sin” (don’t feed bad; all model-makers do this) by spraying a gloss clear coat, doing all your panel lining and decal work and then spraying a matte clear coat over the poor finish. Matte is a rough finish that can hide blemishes, and it’s also a more “realistic” finish. This works more often than not and it saves you the time and headache of stripping paint. The downsides are that you lose some customization options, you will be restricted to a matte finish, and won’t be able to get a satin or gloss finish later on. If the finish is very rough like the first picture in this tutorial, you won’t be able to panel line and it may affect your decals, so use your best judgment if you find yourself in this situation. 

This is the same spoon from the beginning of the tutorial with a matte clear coat on top. As you can see, it’s not perfect but it has definitely improved and is acceptable.

All in all, the best thing you can do is go to the dollar store and buy the biggest pack of spoons you can find and get to work. It’s a little bit of a time investment and painting spoons it’s pretty boring, but it will pay off greatly. Matte finishes are usually the easiest to work with. Satin is a little more difficult and gloss is the trickiest because the sheen shows everything, but with a little practice you will be able to get what you want out of your paint job.

I tried to keep this article short and to the point but if you would like to go more in depth on the subject of airbrushing I highly recommend Airbrushing for Scale Modelers by Arron Skinner. It is one of the greatest books on model making that I have. 

As always remember to stay safe and wear an organic vapor-rated respirator and eye protection when airbrushing. Even with water-based paint. Treat your lungs with love and respect. 

If you decide to use both water and solvent-based paint in the same project, be sure to clean out your brush really well before swapping between them. I noticed while writing this tutorial that the solvent thinner causes the water-based paint to curdle. When that happens, your airbrush will get clogged or start spraying chunks.  

Keep in mind that at the end of the day, this is for fun, so don’t stress out too much if your finish isn’t perfect. My goal here is to show you how to get what you want out of your airbrush.

If you enjoyed this article please share it with a fellow Gunpla builder or leave a comment.

Megaplamo has been building plastic models since 2001. When not building he plays the guitar, bikes, and travels. He lives near the Gulf Coast of Alabama where he and his wife are teaching their two cats to become productive members of society. You can follow @megaplamo on Instagram for current projects, completed projects, and Gunpla building tips.