Monday, December 9, 2013

A Matter of Opinion: How To Thin Paints

Considering my most recent experiments with painting the Tohaa figure from the Infinity range, I thought it appropriate to bring up a topic that has been debated in the past. Specifically, what to use when thinning out your paints.

I've heard many different options, from Flow Aid to dish soap, acrylic thinner to the official Lahmian Medium now put out by GW. I also don't want to forget the tried and true water option as well, though people differ on whether or not tap water is good enough, or is distilled water the way to go.

But what should we use? Does it even matter?

What I won't be debating is whether or not we should be thinning our paints. This is already widely accepted as a need. For those of you who think dipping straight from the pot is acceptable, I would simply ask that you read on with an open mind.

Why don't we list out the options, and see where that takes us. I've got my own opinion, but I'll save that for later.

Liquitex Flow Aid

This is a paint additive that many like to use. It's touted to improve the flow, absorption and blending of any water-soluble paint. My main problem with Flow Aid is that it specifically says in it's own description, that it contains no binding agent, and applying to to a non-absorbent surface may result in poor adhesion. A bonus though, is that it has a slight drying-retardant effect. I've known folks who love this stuff though, so I can't knock it completely, I just hesitate to use it because of it's own disclaimer.

Acrylic Thinner

Testors, Tamiya, and other companies all make acrylic thinners, or mediums, that you can use to thin your paints. The benefit to using these, is that they formulated the same way our paints are, and bond/mix extremely well with the paints. Many folks will use them to thin out hobby paints for use in an airbrush, and for that purpose, I would highly reccomend them. Tamiya and Vallejo both put out thinners that work well for airbrush use.

Dish Soap

Yup, you heard me. There are a ton of folks out there who swear by the use of a bit of water, with a drop of Dish Soap added in to thin their paints with. The reason why I separated this from the water options is specifically because of the soap additive. Honestly, I've never had luck with this. Too many soap choices, all formulated slightly differently, will give too many random results. This is me being picky, maybe, but I like consistency in my paint, and I like my dish soap reserved for scrubbing resin.

Lahmian Medium by GW

Please see the above entry for Acrylic Thinner. Do not buy this horribly over-priced little pot of acrylic medium. It won't work better with GW paint, or any other paint than the Tamiya brand will, and you'll get more for your money with any of the others than with GW.

Tap Water

Very doable, and I've used it many times in the past. You, or your parents, are paying for it anyway in your water bill, so why not use it for your hobby? The main downside with Tap Water is that some folks have a high calcium concentration in their tap water, and if you like to use a wet palette when painting, that can actually do bad things to your paint if you let it sit to try and use it again later.

Distilled Water

Notice I said "Distilled", and not "Bottled". There is a difference. I've had to use distilled water ever since I bought my house, because the water in the town where I live has a notoriously high calcium content. Yes, I spoke from experience in the above statement. Distilled water is a pure water that is perfect for thinning paints. A gallon of it typically costs under 2 dollars, and can last a long time.

The one thing that water doesn't do, is add anything to your paint. everything else added something in it's make-up to the paint to thin it, without losing part of the make up of the paint itself. Water, however, adds nothing. That leads me to my final entry:


Be they GW washes, or Secret Weapon (the only two I've tried this with), washes are an excellent way to thin your paints. Just don't ever use an ink to thin with. it won't work because it has a different make-up than acrylic paints and washes do. See, while every option above does indeed thin your paint, it doesn't add to the pigment ratio while it thins. Using an acrylic-based wash, though, does add pigment, so your ratio of pigment to liquid make-up doesn't decrease!! The only kicker here, is that you will change the base color of the paint you start out with when doing it, as you're basically mixing colors here. Just keep that in mind.

In the Tohaa Infinity figure I just finished, I used Washes exclusively to thin my paints with, and I couldn't be happier with the results.

So what would I choose out of the options I listed? Depends on what I was doing. For airbrushing, I would invest in some Acrylic Thinner, but for painting, I will stick with either Distilled Water, if I don't want my base color to change, OR a Wash if it called for it.

In the end, it's all just A Matter of Opinion anyway. What's yours?

- TIm



  1. I have just started to use a wet palette and found that I don't need to thin my colours as the paint on the palette starts to thin pretty much straight away (so technically I use water to thin my paints :) ). I have never thought about adding washes to colours but am concerned about colour matching if this is done numerous times. For metallic paints I tend to use an acrylic thinner as they do not work too well when mixed with water, due to the pigments in them.

    1. The point about acrylic thinner for metallics is a perfect idea! I will agree that while color matching could be an issue with using washes, it's no different that mixing paints.

  2. I know a lot of people who use windex. I use water for bristles and am now exploring various types of thinners for very fine AB work at lower PSI.

  3. I've tried all the various methods and my favorites are either water (in either form) or acrylic thinner.

    The issue I have with water is the surface tension. It easily pools up which can lead to paint accumulating at the edges of the pools. The acrylic thinner actually lowers the surface tension and, while the paint can still pool, it happens on a smaller scale and with less frequency.

    As for Liquitex. It works. I know the disclaimer on it says it shouldn't, but it does. I have a couple miniatures I've painted using Liquitex to thin my paints and the paint job is just as durable as any other medium.

    Quick note to everyone. If you are someone that likes to stick your paintbrush in your mouth... Stick to water. On the other hand, if you are trying to break yourself of that habit... changing your thinning medium is a pretty good way to do it.

    1. ...does the other thinning mediums just taste bad, or are we talking toxic? Cause if it's just taste, washes and metallics taste pretty nasty as it is.

  4. Acrylic thinner for my airbrush and water for my standard brush. Never thought of using washes. I'll have to try that! Thanks!

    1. You and I see eye to eye on these then, but definitely check out the washes :). Especially if you're used to and comfortable with mixing paints.

  5. The wet palette keeps things about right for my purposes, though I'll usually go with a reasonably wet brush as well to help it flow even more. Lot of drybrushing to my technique though too, and that's the antithesis of thinning. Heh.

    Good article, man - hadn't even thought/heard of several of the options you mentioned!

    1. I would actually argue that drybrushing has nearly as much in common with thinning your paints for painting as anything else does.

  6. outstanding Article, I thin most my paints, and washes with water. However there are some colors that I specifically use a thinner for in my airbrush because it just creates a better final result.. I am lazy though and try to get by with just water because it's easy lol. =P

  7. I attended an airbrushing seminar run by Mr.Justin of Secret Weapon Miniatures at Nova this past year. He recommended thinning your paint with alchohol. I've been using it for several months now and have noticed a night and day difference in my airbrushing. . . I'm no longer spending more time cleaning the airbrush than I do painting!

    1. this was the old rationale behind using car screen wash to airbrush with (which i have done) ultimately tho i returned to acrylic medium for the improved adhesion and the fact of retaining the binder meant that the paint was thicker, (closer to milk) - with the alcohol it was a wee bit too thin for my taste.

  8. I'll throw my hat in the ring here and offer the differing opinion, in that I use Flow Aid (for brushwork)

    I've used a lot of the above, windex, car screenwash, water, acrylci medium etc etc, and I do sometimes use washes, but my go-to is a dropper bottle of dilute flow aid.

    I do use a beastly primer (halfords car - grey) so that might affect my adhesion, but ive never had a problem, except maybe once or twice where i had a flawed batch of resin or was remiss de-vaselining a Greenstuff sculpt.

    I do find that as I use a lot of vallejo paints, flow aid helps prevent the seperation of pigment a lot of people worry about with that brand of paint, and moreover I found it helps me get a good break of surface tension and consistency for layering and blending and making washes.

    Ultimately though it's all about what works for you, and to further add I dont think we can underestimate the variance that temperature and humidity can have on these conversations, I'm in the UK so compared with someone in say, New Mexico, we will have very different conditions under which to be comparing these products.

    Good post tho - this is the stuff we dont often talk about.

  9. Hate to be having to support GW but I have to disagree with your point about their medium... Despite my initial qualms (about the stuff being super overpriced etc) I've found it to be pretty fantastic at thinning out washes and other paints to a wash consistency... I just results in a much smoother finish without any tide marks etc.

    I certainly wouldn't use it for just thinning out paint for layers/base coats however for fine glazes/washes for high level painting I've found it invaluable (particularly for beginners) as it takes a bit of the learning curve/frustration out of the juicing/glazing technique for achieving smooth gradients.

    Paint mediums are not created equal, if you want a medium that works for your paint line I'd always recommend choosing the thinner made by that company as it has been formulated to work with that paint brand.

    That being said I personally feel that a lot of mediums are overrated...

    Personally the ones I use are the Lahmian for glazes/washes and then the liquitex drying retarder for any sort of fine work or freehand.

    Just my opinion, thanks for the article, I've been following your stuff for a while but never through out my own opinion...

    Here's a link to my website/gallery just to add a bit of credibility to my point of view:

  10. I've also used washes to thin paints, and I think they're also a great way to deposit paints into hard-to-reach areas of the models, like nooks and crannies, when you want to deposit paint there, not just a wash. You'll end up using a slightly different color of wash vs. the paint, so by altering how much wash and paint are used, you can vary your paint job as you paint, preventing you from having a "flat" surface of paint.

  11. I found all this discussion to be highly informative and helpful. I'm starting this hobby up and got myself a set of Vallejo paints for my Descent 2e figurines. Might just grab some Vallejo thinner as was stated above, I would hope the same company for both paint and thinner will cause them to work together the best.

  12. Thank you for sharing this interesting and informative article, painting with airless spray gun will be faster and more interesting!

    Spray Machine

  13. Thanks for the explanation!
    You could use Elcometer to measure paint thickness