How and Why to Thin Acrylic Paints for Models and Miniatures

Acrylic paints are often used for painting models and miniatures because they are of high quality and can provide you with great versatility.

Many of these paints are usually thick, and this isn’t always the most helpful for getting a clean result on your workpiece.

In order to achieve the best results, thinning acrylic paints can provide a smoother and more controlled finish.

How and why do you thin acrylic paints for models and miniatures? With the use of water or other paint thinning solution, you can easily thin acrylic paints. Thinned paint is used to create a cleaner finish on the model or miniature you are painting and makes it much easier to control the movements of the brush with paint that is evener.

My goal is to show you how thinning paint can produce much better outcomes for your projects and make your life easier in working with these acrylic paints.

Whether you are just getting into working with acrylic paints for models and miniatures or you want a refresher, thinning is a simple process that will make your projects simpler and more successful. 

Still in the process of gathering the basic tools and supplies? A bit confused as to what you really need?

No need to worry! I’ve been there and done that. I’ve found what’s fantastic to use and what was really a waste of money.

In my latest book, The Miniature Painting Level Up Guide, I take you through all the essential gear, explain what to do to immediately to improve, and which toys, I mean tools, you’ll want to add to your collection as you become more advanced.

If you’re serious about the hobby and plan on getting a good guidebook, this is the one. All you need to know in one convenient place. 

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Ways to Thin Acrylic Paint for Models and Miniatures 

Different types of acrylic paint will respond better to different methods for thinning.

There are multiple options you can choose from, and I’ll cover the most popular and successful ways to thin your acrylic paint.

This will include how to use them to achieve the best results on your figure. 

Just so you know, your results will depend heavily on the products and equipment you’re using. Check with my miniature painting gear page to see what I have found through personal experience to be the best.

Water: The Primary Acrylic Paint Thinner

Water has been used to thin acrylic paints for a long time because it is not only effective, but it is readily available and cheaper than other thinning solutions on the market.

Mixing water into your paint can help to achieve a smooth and consistent finish in both the texture and the color.

When mixing water and paint, you must be very cautious not to put in too much water.

Here are the steps to using water for thinning your acrylic paints. 

Evaluate the Acrylic Paint Thickness

You should open the acrylic paint you will be using and evaluate its thickness. If you can see it is quite thick and does not easily flow in the bottle, you know you will need to thin it.

Fill a Separate Cup of Water

You will want to keep the water separate and not pour it directly in the paint as the ratio is very important.

Too much water can compromise the paint and damage the results you were hoping to achieve. It is suggested that the water not comprise more than 50% of the mixture.

Put the paint into a separate cup and mix with water, so you do not pour too much into the paint container.  

Mix With a Brush

Start to mix the water and paint and apply it to a piece of paper or another surface to test before use.

You should notice that the brush glides smoothly and creates a consistent thickness and color.

You can also dip your brush into a little bit of water and paint and work with smaller amounts to start.

Apply to Model or Miniature

Once you have your desired thickness, you can apply it to your model. This should be done one layer at a time and let dry for the best results.

You can also check out the video below to see how this process of mixing paint and water is done and what a difference it makes to the way the paint spreads. 

Paint Additives 

There are other solutions you can add to your acrylic paint if you do not want to use water. The reasons to include other types of additives include: 

Worry Less About Ratios

You won’t have to worry about keeping consistent and careful ratios like you would with water. This makes it easier to use and prevents ruining any paint.

You should still be aware that more additives will still weaken the amount of pigment present.  

Unique Techniques

Different paint additives can create varying levels of thinness and different characteristics that can allow you to achieve more unique techniques than the thinning that water produces. 

Additives are used to change the properties of paint, and they are one of the main ingredients in acrylic paint.

There are a variety of separate additives (more on that here) you can put in addition to the original acrylic paint to change the consistencies and properties even further.

We will dive into these different additives, but you can also watch this video for some more demonstrations!

Thinner Medium 

Thinner medium is a solution that can be used to thin your acrylic paints by allowing the pigment to spread out.

The thinner the medium that is used, the greater the dilution of the pigment will be.

You can use these products in smaller amounts to ensure that the paint will be thinned for an easier application while making sure that the colors will not be impacted.

Thinner mediums come in multiple varieties, but I suggest using one that comes out of a dropper bottle, like the one I use.

It works perfectly every time, and it not only can thin paints and primers but can function as a flow aid too.

Dropper bottles make it easier to transfer paint to your palette, and you can gauge the amount of thinner medium you are using more easily.

You can also add it onto a brush and mix in with the paint to reach a thinner consistency that still maintains the color you desire.

Using a thinner medium can dilute the color and thickness to your desired preference. You can see this process being done here with comparisons.

The main reason that someone would use a thinner medium over water is that it will always be a consistent mixture versus water, which can vary in quality as well as its hardness.  

Thinner mediums come down to your preference, but they can be a bit more consistent and predictable than using water.

You should use small amounts of paint and thinner medium on a palette (Masterson Sta-Wet is excellent) or plate to find consistency and pigment that suits your needs for the model or miniature.

You can read more about the advantages of using a wet palette here, see what I personally use, and learn how to make a perfectly usable DIY version yourself.

This method is typically used for brush applications of acrylic paint. 

Flow Improver / Flow Aid

Flow improver and flow aid are used interchangeably, depending on the brand you are using.

They are used to improve the consistency of acrylic paint so that it can be applied more efficiently and smoothly.

Its primary purpose is to thin the paint without taking away the strength of the color and keeps your desired finish.

Flow aid is a solution that will reduce the viscosity of the paint. This helps to achieve similar paint thinning results by giving the paint and flatter and a more finished look.

With the application, you will not see the thick buildups of paint like you would with your original acrylic paint.

The appearance of the paint on your models or miniatures raises the quality of the product.

I explain more about flow aids here, including why you should use them and what the best choices are.

Personally, I use this one from Amazon. Although it can be used right out of the bottle, I like to water it down to a 5 to 1 water/flow improver ratio. I haven’t found a better product for the job yet. 

In order to use flow aid, you can follow these steps: 

1. Blot paint on the palette: You want to put the amount of paint you plan to use for your model in a specific color. This will help to ensure you create the same consistency for all the areas you plan to paint one color. 
2. Place a small amount of flow aid on the brush: You should add some flow acid to your brush, starting with a small amount so that you do not make the paint too thin. 
3. Mix solutions: Brush the flow aid into your paint to fully integrate the two. You can add more if this still appears too thick. Thicker paints will require more flow aid to reach your desired consistency and viscosity. 
4. Apply to figures: Once you are happy with your thinned paint, apply it to the figure. You should notice that this paint has a flat texture and appearance and is easier to control. 

You can watch this process being done to see the difference between the quality of a finished product when using a flow aid versus the paint itself.

You should be applying multiple coats to your models and figures to achieve both a flat texture and the vibrant coloring you desire.

Airbrush Paint Thinner

Unlike the other paint thinning solutions that are being applied more commonly with a brush, you can also use paint thinner in an airbrush application.

(Head over to this article for a more in-depth look at thinning paint for an airbrush.)

You are still thinning the paint to achieve a more consistent and smooth texture and application, and you are mixing these solutions outside of the airbrush in a similar way.  

You use different solutions to effectively thin airbrush paint: 

• Deionized water: This is the water option, but you should be using this type correctly because it will prevent rust and is one of the cleaner options to use. You can find this at a grocery store, and it is very inexpensive.  
• Airbrush thinner: This is a step above water in terms of quality and application. You can either buy a premade thinner (which is suggested since it is already a perfected recipe), or you can make your own thinner.

To make your own thinner, you will need to combine 1/3 Isopropanol, 2/3 deionized water, and two drops of retarder.

You can add these individual ingredients to your solution to change the properties of the paint.

The airbrush solution that is premade will look similar to those used for paint thinners but is typically sold in a larger bottle. 

I recommend that you mix your thinners and solution with the paint outside of the airbrush.

As this helpful video shows, you will not be getting a consistent mix of the two if you put paint or thinner into the airbrush itself and then follow with the other material.

Try mixing outside in a small dish and then transfer once you have the consistency that you desire. 

The process for creating thinned airbrush paint for your models and miniatures is very similar to the method you would use with a brush.

You are still combining these liquids to the side so that you can determine if it is smooth and thin enough.

Having thin enough airbrush paint is helpful so it can easily flow out of the airbrush during application.

If you haven’t made the leap and purchased an airbrush yet, be sure to read my “Guide to Airbrushes” for a complete breakdown of what’s what.

Then, check out my top recommendations for the best compressors to pair them with, and you’ll be all set!

Why You Should Thin Acrylic Paint for Models and Miniatures

As you can see, there are a variety of ways to thin your paint, and these lead to favorable outcomes for your models and miniatures.

We are now going to go into a bit more detail of why you should thin your paints and how these results lead to an overall more finished and high-quality appearance.

Here are some of the positive outcomes of thinning your acrylic paints. 

Consistent Coloring

When you thin your acrylic paint, you are creating a larger and smoother pool of paint color that will be applied evenly.

When the paint is not even, some of the coloring will be richer and thicker on your models and miniatures in some areas because you cannot control the levels of application.

This lack of control will make it look darker in some regions. By using thinner, the color can be applied evenly in one coat and darkened with more coats.  

Avoid Brush Marks

By thinning the paint, you avoid the varying levels in thickness and texture that can result in seeing the brush strokes you place on the models.

Visible brush strokes do not give a refined look to your finished product. Paint thinning will eliminate these differences in texture and appearance to give you a smooth and flat finish. 

Save Paint

You will also go through less paint when you thin it as you are not getting build-ups on your models and miniatures. The thinner paint can cover more surface area than the original thick acrylic paint can. 

Prevent Clogging

With thick acrylic paint, it tends to build up around the detailing on your project. It can fill cracks and details with lots of paint instead of just covering the surface of the figure.

This creates a messier look that is not as refined as a thinned paint will appear.  

Control of the Brush

With a thinner paint, you can make more precise brush strokes and achieve attractive results in detailed work than you would with a thick glob of original paint on your brush.

What brushes do you need for quality painting? Find the answer here.

With models and miniatures, the details matter, especially when using paint in small and precise spaces.  

Range of Techniques

Paint thinning allows you to make your paint applications more unique to give your models and miniatures very specific looks.

These solutions give you much more creative freedom than a thick acrylic paint will. All of these results can be achieved when you thin your paint successfully.

You should be aware of how much thinner is being added to the paint so that you can make the consistency you want while still maintaining the intended color (unless your goal is to change it).  

Thinning Acrylic Paints for Models and Miniatures 

Now that I have shown you how to thin your acrylic paints and why it is important, let’s touch upon how you can improve your skills to get the paint thinness you want consistently.

This will make it much faster to mix your paints and allow you to spend more time in the application phase. 

Be sure to explore all of my articles on miniature painting for tips, recommendations for the best products out there, and answers to your painting questions.

You can work on your acrylic thinning techniques in the following ways. 

Practice Combinations

You will need to add your thinning solution to paint over and over so you can figure out which consistency comes out with the best results.

You can try this on a piece of thick paper or unimportant surface. Mix your solutions thoroughly and then practice using your brush to draw controlled lines.

Notice differences in color as your paint becomes thinner and thinner. 

Experiment

Use different amounts of the thinning solution so you can see the impact it has on the paint from an artistic perspective.

Making it thin and opaque (also known as a ‘wash’) could look cool on some parts of your model where others would benefit from more vibrant hues.  

Use Different Thinners

Try using water, thinner mediums, and flow aids to see which works best for you. You may find working with some solutions easier than others and that they yield different results. 

Summing It Up

Thinning your acrylic paint is a relatively simple process once you get the hang of it. Practicing with small amounts of paint is the best way to achieve your desired results.

Thinning the paint is not only easy, but it leads to a significantly better outcome for your models and miniatures. These small changes in paint thickness raise the quality and appearance of your work.

With multiple solutions to choose from, with water being the most popular and thinning mediums being the most consistent and effective, you can play around with which solution works best for the paint you are working with and the type of project.

I recommend all levels of acrylic painters to thin their paints for the best results!

Remember, this is just one of the many topics I cover in The Miniature Painting Level Up Guide. Get your copy today to see how to steadily move from a beginner to a pro in no time!

Image Credit: Henti Smith