Wargaming Tradecraft: Types of Thinners

Types of Thinners

When making your acrylics (normal water based GW, P3, etc paints) thin enough to airbrush, you'll have to add something to the paint. By default, most of us will just add water until it's thin enough to spray without clogging and thick enough to not be a wash and to still have some colour. Instead of water, there are other mediums you can use - each has benefits and downsides.

Any of these thinners work well, some better than others depending on the situation. It’s also helpful to mix different mediums and aids together. What’s the perfect mix? People spend a lot of time concocting potions of paint thinners - not just for airbrushing but even to mix with all their paints.

I also have an overview of using thinners with airbrushes.

A bunch of these supplies are available in my Wargaming Approved supplies list.

(Unfortunately, it's kinda hard to tell the difference in this photo, but I'll explain them below.)


The easiest, most available of thinners and free! (well, mostly) This’ll work in a pinch and really there’s nothing really wrong with using it.

Thinning with water quickly turns your airbrush paint into a wash. Great if you're washing, not if you're painting, so careful not to thin too much.

You'll also notice as you thin with water that you lose the strength of your colours. (Hence, the whole wash thing) Other mediums can actually thin your paints but preserve the strength of the colour - that's why we're here, looking at other options.

As reader Zombie Ad points out, if you live in a hard water area, you may want to use some form of bottled water with your airbrush. Having grown up in a city like this, I can only imagine the uglyness of the calcium build up you could end up with in your Airbrush. FYI - vinegar cleans calcium deposits.

Isopropanol Alcohol

I bought the 99% stuff, but it also comes in other dilutions. (such as half water, half alcohol) The more water that's mixed in, the less drastic the following would be. However, DO NOT use rubbing alcohol - this has some oils in it, which will break your paints down.

Very low surface tension and had a great covering.

Test beforehand, because alcohol reacts
poorly with some paints... breaking up
or thickening up.
I found the colour much bolder using alcohol, which was nice. This was because alcohol evaporates quickly, leaving behind the pigments. Like water, but unlike some other mediums, alcohol is a very thin liquid. (Excellent for thinning paints when mixed with thicker mediums)

The downside I found with alcohol is that since it evaporates so quick, the paint dried in my airbrush and clogged basically as soon as I stopped spraying.

Slow-Dry / Flow Aid / Fluid Retarder

These products are designed to help paints flow and mix better and/or increase the amount of time it takes before they start to dry out. (If you're working with a palette)

I tried both the types pictured to the left. Liquitex prints the properties of their mediums on the bottles, and you can see here that the only difference is the second one has a bit of a gloss finish.

The first one here, a clear liquid and finish, is probably my favourite stand-alone medium. I often use it to mix with paints, even when not airbrushing, when I don't want them to dry out too fast.

As an airbrush medium, it thinned the paints nicely and flowed cleanly. The coverage was even and didn't get runny like a wash. While not as strong as the colour using alcohol, it definitely didn't fade as much as water.

This second one didn't impress me too much.

On the up side, the colour was strong and when painted on the mini, the surface of the paint was fine.

However, it was both thicker and a realllll pain to clean. It's opaque (milky) while wet and dries clear. Unmixed, it creates a gummy / plasticy sort of feeling and I wonder if painting it on too thick would create a poor surface to paint over. I'm guessing that something in the milkyness is what's making it all gummy when you get some on you. Cleaning with water created a bit of an oily appearance and assisted in the ensuing clogging.


They come in either Matte (flat, not shiny), Gloss (shiny) or Satin. (in between) A medium will thin a paint, bonding cleanly with the colours, which keeps colours stronger and more vibrant than if you use water.

The colour was really nice using this stuff, but it was about as thick as the paint itself. Not useful by itself for airbrushing. (Though I imagine it'd be nice if you're just brushing the paint on) I had to really open up the pressure and spray to get this stuff to flow.

It's worth noting that when mixed, this helped the paint go further (diluted) while keeping it's colour.

"Airbrush Thinner"
example not displayed

I picked up something billed as airbrush thinner to try out. It’s hard to give suggestions on this because I’m sure you’ll find different concoctions depending on where you go. Usually, this will be a combination of multiple thinnes to get different properties in your paints. Google around and you'll find that many artists prefer to create their own thinner by mixing multiple agents, and often disagree with what's the best mix.

After experimenting with my mediums and some thought, I think the "airbrush thinner" I bought is a little heavy on the opaque slow-dry and/or matte medium.

example not displayed

A bunch of people have suggested using Windex... probably because of how quickly it evaporates. I imagine it'd act similar to alcohol, but wouldn't evaporate that fast.

I didn't test it however, because Windex contains ammonia - this can damage the metal of your airbrush.

Create Your Own Mix

Once you've bought and tried out some different thinners, you can create your own mix from the best. Here's mine.

The matte medium and slo-dri gave the best colour, so I used 1 part of each of them. To thin it out even more, I used 2 parts alcohol. This gave a mix of great flow and strong colour. After testing it out, seems it worked quite well.

1 part Matte Medium : 1 part Slo-Dri : 2 parts Alcohol
For those not familiar with the whole "part" stuff, it works like this:

  • Using the above example, I have medium [M], slo-dri [SD] and alcohol [A].
    • Say I put in 10 mL of M, 10 mL of SD and 20 mL of A.
    • This is also represented as
      • description - 1 part M, 1 part SD and 2 parts A
      • ratio - 1M : 1SD : 2A
I'm just pointing this out to avoid any confusion... The numbers can be any mix you want. I didn't use 2A because 1 + 1 = 2... I just knew that I needed more alcohol than medium and slo-dri. So, I started with 2 parts alcohol, and if it needed to be thinner, just would have added another EQUAL part of alcohol. (1:1:3)

If you think it's a little too thin or a little too thick, don't just add more of something all willy nilly. You want to be able to recreate what you're mixing so that the next time you need more airbrush thinner, you can make the same mixture as before, so it works the same. That's why you want to work with "parts" - you know how much to add in relation to everything else you're mixing in. If you start "I'll just add a couple more drops of ____" then you won't be able to keep track of measurements to recreate it.

If you hit up a drug store or a Walmart, you can buy cheap plastic syringes (without a needle) that will let you mix liquids and have a measurement on the side for keeping track of how much you're adding. Or, use a marker to draw lines on your container at the level each liquid should be poured to.

Take a look at the Wargaming Tradecraft Techniques Page for links to the entire Airbrushing series and other tips, tutorials and information.


  1. A note on water. Depending on where you live you might want to substitute with distilled or ionised, espcially if you live in a hard water area.

  2. Fow Windex, you can get non-amonia window cleaner that works pretty well for cleaning airbrushes.

    Personally, though, for thinning I use Createx Airbrush Medium. I've been using GW Foundation paints (astronomicon grey for my Space Wolves primarily) and I found that water or Windex just didn't suspend the paint all that well. It would work for a little while, but if I stopped spraying for even a little bit, then the pigment would settle and start clogging my brush. I'd have to constantly mix the paint in order for it to work. Once I got the airbrush medium, I was able to mix it about 50/50 and get a nice consistency that I was able to use for a lot longer.

  3. @Zombie: Thanks for that note... I didn't try other waters, but I wouldn't want calcium caking into my airbrush. I'll update the post and credit you.

    @rkik: Cleaning, yes.. but people talk about using Windex to thin your paints. Since the point of using it is for the evaporating of the ammonia, there's probably no benefit to using non-ammonia Windex.

  4. Thanks for the post, as an airbrush enthusiast, I appreciate the info.

    I use either alcohol, or airbrush medium.
    (I use the "golden" brand, not the createx, but I am sure they are similar) and find it works very well.

    I do have to say, that while I don't mind mixing paints, I really have found using actual air brush paints to be a million times easier, and not that much more expensive.
    (I use either vallejo model air, or golden airbrush paints or occasionally createx).

    thanks for the post.

  5. Great article! Man, are you sure about the ammonia hurting the airbrush? I've been using windshield cleaning fluid for about a year now and I haven't noticed any pitting or discoloration, but that certainly doesn't mean it won't happen, or already has. *That* would be a bummer.

    An observation about alcohol: I've noticed that when mixing GW paint and alcohol it almost seemed thicker, but lighter somehow. It's hard to describe. Less fluid but less dense? Almost foamy, but without any visible bubbles. That concerned me. And it made an odd sound while spraying, like it was forcing out air as well as paint. I'm using 70% isopropyl b/c that's all the corner drug store had, and drop of retarder as the alcohol tends to clog immediately (I suppose that combo could be the culprit).

    1. There's a lot of info out there on ammonia damaging various metals. It's probably a concentration thing. As I understand it, you'll get dulling / reduced luster before actual pitting. They usually have a protective coating, at least on the outside.

      Alcohol's a funny thing when used as a thinner. I haven't tried it with GW's newest line of paints. It will clog your airbrush quicker as it evaporates fast. You could try some more retarder. Only thing I can think of regarding the foamyness, is maybe you got some soap residue left from cleaning the airbrush?


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