How to Thin Hobby Paints for Miniatures (10 Useful Ways)

Water is abundant, non-toxic, and free. You can thin all the model paints you want with the water from a faucet tap.

Quick tip: For best results, you can filter your water to remove hard mineral contaminants that may interfere with your paint’s chemistry. You can read more about hard versus soft water in this article.

The limitation of water as a thinner comes from the need to know how much to use. How much water should you use to thin your acrylic paints? The answer depends on many factors, including how thick your paint already is, how pigment rich is your paint, and what you plan to use your thinned paint for, e.g., glazing, washes, or layering. All these factors and more will determine how much water you’ll need to thin your model paint.

In general, you should use the least amount of water as possible to achieve the effect you’re looking to create whilst maintaining good control over your paint flow (a key point as you’ll see below). For example, in normal painting as a default, add just enough water so your thinned paint flows well off your brush as you use it. Note some paints, e.g., Vallejo Model Air, may not require any thinning at all. You can use these airbrush-ready paints straight from the bottle with your regular brush.

Too much water will overly thin your acrylic paints, which does two bad things. First, if you thin your paint with too much water, you will lose the binding property of your paint. This leads to a loss of paint control as you apply it. Your paint will be too runny and won’t go where you need it to go. Paint will drip.

Second, when you use too much water to thin paint, you may end up with a splotchy finish, e.g., coffee stains on your model. This is because the pigment in your acrylic paint will follow the surface tension of the water (pooling at the edges of your brushstroke) instead of spreading evenly through the medium as it dries. In other words, too much water leads to a bad paint finish.

Overall, when in doubt about using water as a thinner, you can follow this rule: the paint should slide from your brush, not drip or clump.

2. Inks and Shades

Did you know that you can use inks to thin your acrylic model paints? Inks are different than regular acrylic paints in several ways. For example, inks (and even the hobby grade inks, like Scalecolor’s Inktense or P3 inks) use a liquid pigment or dye for color, instead of the solid ground pigment in normal acrylic paint. Because of this, inks have a much lower viscosity than any regular acrylic paint, yet maintain their color richness.

The advantage of thinning miniature paints with inks is that you increase paint flow off your brush without messing with the ability of the paint to cover your models. Additionally, the low viscosity and high color saturation of inks make them a great choice for thinning other acrylic mediums without losing color vibrancy and coverage, which may happen if you thin with simple water (e.g., your paints become too transparent).

RELATED: BEST 15 INKS FOR PAINTING MINIATURES AND MODELS

Of course, a notable limitation of thinning your paints with inks is that you will distort and change the hue and value of your colors. Also note that ink-thinned paints will usually be darker than the original color. This isn’t a bad thing, instead it’s merely a side-effect you will need to account for when you thin paints with inks that have their own color depth.

Depending on the type of ink, the final color and “thinness” of your ink-paint mixture will vary. So you’ll need to experiment with your ink-paint combo for your particular application. Quick tip: Because inks have high color saturation, you can thin inks alone with water and create wonderful glazes that keep their transparency and help you create smooth color blends on model surfaces.

I also find that ink-paint mixing work great for weathering terrain or vehicles. You can create streaky grime, alien blood splatter, or splotches of interesting color on craggy rock faces, e.g., mold and the odd growth, or simply add a bit of interest to a bare warehouse building. Because inks will generally darken a paint color, you can also use inks for shading mid tone base paint colors, which allows you to create natural, more realistic-looking shadows. Give inks a try!

3. Glazing Mediums

The use of glazing medium for thinning paint is very popular for different reasons. Although, I’ll note here that some glazing mediums actually have more viscosity (e.g., they are thicker) than most hobby paints. For this reason, you’ll want to continue using water along with glazing mediums if you’re looking for a more “thinner” painting experience. Obviously, glazing mediums are perfect for creating glazes with hobby acrylic paints.

When using glazing mediums, less is more. Here’s what I mean: If you add too much glazing medium, you may have paint layers that hide and fill-in small details on your miniature’s surface. So, instead of using pure glazing medium, you’ll want to mix your acrylic paints with just a tiny bit of glazing medium along with water until your paint mixture flows easily from your brush on your model’s surface (not runny or drippy!).

The exact ratio of this glazing medium/water/paint mixture will depend on the type of paint you’re using, the glazing medium thickness, and what you need to do.

As starting point for mixing glazing medium, start with a 1:5 ratio of glazing medium to paint, and thin to taste with water. The great thing about glazing mediums is that mixing it with acrylic paint does not disrupt or dilute the natural binding properties of the paint. You won’t get a splotchy finish and the paint will coat your surfaces smoothly.

Glazing mediums will make your dried paint finish glossy. For most model painting, a matte or satin finish is preferred for an overall complete and professional appearance. A nice matte finish will also make good photography easier, preventing the harsh reflections that can make your models look unfinished or messy. Here’s my favorite matte varnish sealant for miniatures and models.

4. Flow Aids or Improvers

Flow aid is a surfactant (or a soapy substance) that breaks up surface tension. For thinning hobby paints, there are a few flow aid brands I’ve tried and recommend. Here are 3 that work great with acrylic model paint: Winsor & Newton Flow Improver, Liquitex Flow Aid, and Golden Acrylic Flow Release. For all of these flow improver additives, you’ll need to dilute them with water (usually in a 1:10 flow aid to water ratio).

The great thing about flow aids is that they can help you in a variety of miniature painting techniques. You can create your own acrylic washes, glazes, or even help you with wet blending in certain situations. Because flow aids are potent, even after you dilute them with water, they will continue to exert a powerful effect on your paints. Use a tiny amount with your paint mixture at a time.

A word of warning when using flow aid in your acrylic paints. Flow aids and improvers are usually toxic and harmful when ingested or inhaled. While licking your paint brush to keep a sharp point is a popular practice, this poses a personal risk when painting with flow aids and improvers. Moverover, although some may suggest using flow aid to thin paints for airbrushing, I do not recommend it. Inhaling aerosolized flow aid can be dangerous. Use an airbrush spray booth to reduce your risk if you must continue, or use a dedicated airbrush thinner medium (see below).

Here are some other practical considerations: flow aids will speed up paint drying. This isn’t really because of the medium itself, but rather that your paint “spreads out” and is exposed to more ambient air. If you’re using flow aids, just remember that you may have to work faster than you usually would.

Finally, using too much flow aid will make your paint much harder, if not impossible, to control. If in doubt, use water first to thin your paints, and a itty bitty dab of flow aid (less than a drop) to get your paints real thin.

5. Varnish (Water Soluble)

The conventional purpose of thinners is to improve paint flow and help you create smooth layers, reducing the appearance of brush strokes and retraining surface detail on your model. If paint goes on too thick, you will have a messy, amateur paint finish. The best thinners should also allow you to control where paint goes, too.

Using a varnish to thin your paint has two advantages: First, a varnish mixed with your paint will maintain the acrylic polymer property of the paint, so you don’t lose surface adherence to the model, e.g., paint sticks. Second, a varnish improves the surface reflectivity of your dried model paint. That is, you can mix in a water-soluble matte varnish and create a less glossy paint surface. This really helps for blending different colors through layering and glazing.

Whether you mix a gloss, matte, or satin varnish into your paint, another effect is that varnishes will make your paint colors translucent. This is really helpful for making glazes. In fact, mixing varnishes into your paint is similar in principle to adding a dedicated glazing medium. Both will do similar things, except with a matte varnish, you will have a less glossy surface when dry. Taken together, a varnish can add tons of versatility to your painting toolbox and workflow. You can be more creative.

I use Reaper Miniatures Sealer to help me glaze model paint colors on large or small models, and especially when I want the layers to retain a matte finish as I work. The Reaper Miniatures Sealer is one of my favorite mediums for acrylic glazing and I have a fairly large stockpile of unopened bottles. They are that good!

Of course, make sure you consider adding some additional water to your varnish and paint mixture to reduce your viscosity and improve paint handling off your brush and on your model. As with glazing mediums, don’t use too much as your paint may become too transparent to your liking, and will severely reduce color coverage, which can reduce texture detail on your miniatures.

6. Airbrush Thinner

Of all the acrylic hobby paint thinners (other than water), I prefer using airbrush thinners even with regular brush work. Airbrush thinners are similar to flow aids and improvers in that they break up surface tension and greatly improve paint flow. This, of course, helps model paints flow better through an airbrush.

RELATED: AIRBRUSH VERSUS BRUSH: WHAT IS BETTER FOR PAINTING MINIATURES?

The best feature about airbrush thinners, however, as compared with flow aids, is that they slow paint drying. This helps prevent paint from clogging your airbrush. And, it also happens to serve double duty when you’re painting with normal brush on a dry palette or using a variety of wet-blending techniques.

Additionally, airbrush thinners don’t disrupt the natural acrylic binding properties that water will if you add too much. This means that using an airbrush thinner will give you more consistent results in your paint finish. You’ll have an easier time avoiding the “too runny” paint dilemma you may encounter with using water. The exception is that if you understand the correct ratio for using water as a thinner, you’ll be able to do the same thing without the cost of another art medium.

You don’t need much airbrush thinner for most model paints. For example, I use much less airbrush thinner than I would normal water to achieve the same paint thinning effect. This is great because I can maintain color coverage while increasing paint flow, which is something that other thinners can’t achieve.

You’ll want to play around with the best ratio for your application. But, to start, I like using a 1:5-10 ratio of airbrush thinner to paint. If I need to thin the paint further, I’ll either add water or more airbrush thinner. For those wondering what the best airbrush thinner is, I highly recommend Vallejo Airbrush Thinner or Liquitex Airbrush medium. Both work great for model paints, while I’ll note the Liquitex Airbrush medium does add a bit of a glossy finish when the paint has dried.

7. Hobby Mixing Mediums

There are a number of specialized mixing mediums that will help you thin your acrylic paints. Some are hobby-branded, others are typical artist grade acrylic mediums (e.g., clear acrylic polymers or binders). Popular and useful mixing mediums that I’ve tried include Citadel Lahmian Medium, Golden Open Acrylic Thinner, Vallejo Thinner Medium, and Liquitex Professional Fluid Medium (matte).

If I had to choose between these acrylic mixing mediums for painting miniatures, I would prefer artist grade mediums for day to day casual miniature painting work. Hobby grade mixing mediums are very effective for thinning and mixing paints, but they are expensive. But, there’s a reason why!

Hobby mixing mediums make up for their expense by being convenient and easy-to-use. Just add a few drops to your model paints and you’re ready to go. The exact ratio you need to mix for your particular hobby paint has already been worked out and there’s no need to make your own recipe. There’s no guesswork involved.

On the other hand, artist mixing mediums require a bit of technical know-how since you may need to additional water and consider that some art mediums will have undesired glossy finishes (even the matte mediums don’t dry very matte when mixed with model paints). You have to experiment for yourself to see what works for your needs.

In either case, whether you use hobby mixing mediums or artist grade acrylic polymer, your paint colors will become more translucent, e.g., less coverage. This is fantastic for glazing and layering approaches for color blending, as well as smoothing out the rough edges on your base coats (with thinned layers of color).

Quick tip: Don’t use mixing mediums for thinning your paints for your first base coat layers. It’s unnecessary. Use water instead, since you’ll be covering up these early layers of color anyway.

For most hobbyists, I would say that hobby mixing mediums are worth the cost as an alternative to simple water for thinning your paints when you want absolute control over your paint thinning and application. Just note that this will eventually become the most expensive consumable in your hobby if you use hobby mixing mediums regularly.

8. Windex or Other Glass Cleaners

Glass window cleaners like Windex are both useful and effective model paint thinners. They are the “poor man’s” flow improver, meaning you can find these anywhere, e.g., hardware stores, at the local bodega, and in huge quantities for much less money than the artist grade flow aids. These work fantastic for thinning acrylic paints for airbrushing or regular brush work.

Glass cleaners work well as hobby paint thinners because they break up the surface tension in water-based solutions. This increases paint flow and reduces viscosity in a predictable manner.

Ever have trouble with your paint puddling, pooling, or clumping on you model’s surface? Household glass cleaners are great at breaking down any oils or contaminants on your model’s surface, which may interfere with the ability of the paint to stick.

I suggest using glass cleaners for thinning paints that don’t have added fragrances, e.g., lime, pine, and other smells. These tend to be very pungent, and annoying float around you for a very long time. Also be aware that almost all glass cleaners have an ammonia active ingredient. Ammonia is toxic and should not be inhaled or ingested. Avoid licking your brushes when using glass cleaners as a thinner and take safety precautions if you’re going to airbrush.

Note that Windex and other similar glass cleaners will also speed up your paint dry time. (The evaporation temperature of windex is lower than water). This works great for cleaning things around your home, but will make some miniature painting techniques nearly impossible, e.g., wet-blending.

Overall, if you want or need to use a flow aid surfecant, but want to save a bit of money, glass cleaners are a useful and effective alternative.

9. Rubbing Alcohol (Isopropyl, Isopropanol, or 2-propanol)

Isopropyl, Isopropanol, or 2-propanol (aka “Rubbing Alcohol”) is a less common water soluble thinner for model paint. Interestingly, some hobby metallic paints and inks use alcohol as their solvent/diluent. Can you use rubbing alcohol to thin acrylic paints? Certainly! But for the most part, a reason you may consider rubbing alcohol is because it is easy to find and inexpensive. You may already have a bottle stashed somewhere in your medicine cabinet.

The typical 70% concentration of rubbing alcohol you find at your favorite drug store will easily mix and thin acrylic hobby paints. And, higher concentrations (>90%) of isopropyl alcohol may be strong enough to strip miniature paints from your models. In either case, you won’t need much alcohol for thinning acrylic paints that you want to airbrush or use with a bristle brush. Start with 1-2 drops of alcohol in your paint (1-2 parts alcohol to 5-10 parts paint) and see how it thins your colors.

A limitation of using rubbing alcohol as a model paint thinner, however, is that it will significantly speed up your paint dry time. Alcohol evaporates fast at normal room temperature, and as it does, the alcohol will leach the remaining moisture from your hobby paint. This means you should only use rubbing alcohol as a thinner if you already know how and when you will use your paints.

Alcohol is also an irritant to skin, and should not be inhaled if you’re spraying thinned acrylic paint. It is also flammable, so if you’re using a hair dryer in your miniature painting workflow be careful! It doesn’t take much to ignite alcohol fumes. And, when alcohol burns, the flame is invisible (you won’t see the flame melting and setting your hobby stuff on fire, trust me, I know….).

You likely won’t be able to do any wet-blending applications with paints thinned with alcohol. On the other hand, because alcohol speeds up paint dry, you may find it useful for thinning paint for airbrushing. A problem some miniature painters have with airbrushing is having paint that runs too quickly on the sprayed model surface. Alcohol will thin the paint sufficiently to create a nice mist (e.g., improve atomization) and allow you to layer up colors on your model quickly without the runny, spiderly effects.

READ MORE: FREE COMPLETE GUIDE TO AIRBRUSHING MINIATURES AND MODELS

In general, I don’t recommend using rubbing alcohol for day-to-day brush work because of the faster paint dry speed. But, here’s where you may find rubbing alcohol useful with a brush: if you’re looking to dry brush your models, a drop of alcohol in your model paint and a few seconds of airtime will help remove the moisture from your brush (e.g., use a crappy old brush for this application). Then, apply your pigments with the dry brushing technique. Works great!

10. Slow Drying Mediums

Slow drying mediums are exactly as the name implies; they keep paint wet longer. Slow drying mediums come in many types, from thick gels to thinned clear liquids. In general, if you’re going to use a slow drying medium, you may still need to add water to lower the viscosity of your hobby paint for painting minis.

As with any art mediums, such as Winsor & Newton Slow Drying Medium or Vallejo Retarder Medium, you should start with a small amount and see how it affects your paint. Although slow drying mediums don’t affect acrylic polymer binding to your model surfaces, it will reduce your color saturation through dilution.

My suggestion is to add a drop (or two) and see if that slow down your paint drying enough for your application. Adding water may be helpful as mentioned to lower your paint viscosity further.

The great thing about using slow drying mediums for your hobby acrylic paints is that you can perform more advanced paint blending techniques, such as wet-blending, without rushing as quickly to apply your paint. Of course, on the flip side, slowing down your paint dry speed will slow down your productivity overall. You won’t finish painting your models as quickly if your paint dries slowly after applying each layer.

READ MORE: HOW TO SPEED PAINT MINIATURE AND MODELS

For those looking for an alternative to slow drying medium, you may find a wet-palette useful. Wet-palettes are a hobby device that uses a water-porous film placed over a water-dampened sponge. You place your acrylic paint on the film surface (the palette). As the paint dries, water from the sponge underneath the film seeps upwards, keeping your paint wet for long periods of time.

You can make your own DIY wet palette, or buy affordable wet palettes. There are limitations to a wet palette, and I have generally avoided using one for most of my miniature painting work. I tend to prefer using a glazed ceramic watercolor palette for all my miniature painting work. For this reason, I sometimes use slow drying mediums when I paint.

When using slow drying mediums in any setting, you will need to experiment with the exact amount to use. For a start, I suggest using a single drop for every 5-10 drops of acrylic paint (or, 1 drying retarder to 1-5 paint). Mix in some water to reduce the viscosity of the mixture until you’re satisfied. I’ve found that slow drying mediums will increase the time acrylic paints stay wet for up to 30-60 minutes (depending on the ambient temperature and humidity).

Read on for more tips, tricks, and a quick guide about how the process of thinning your hobby paints for miniatures!

Why thin paints for PAINTING MINIATURES?