Tuesday, January 4, 2011

Mediums and Other Paint Additives

Well...not that kind of medium, but close. If you want to stick to the analogy you can imagine that medium is what bridges the gap between your GW paint pot and your model.

In this post I'm going to go over some of the different types of mediums and additives that you can find by the liquitex company. Any of these can be purchased at a craft store such as Hobby Lobby or Micheal's. If you're unable to get to one of those then you can order online from one of the largest arts suppliers, Dick Blick.

Matte Medium

Matte Medium is the staple of your mediums. If you buy one medium, this is your guy. When it comes to GW paints, they're thick. Super thick; Lexington Steele thick. You can dilute it with this stuff by 2 parts and still get good coverage. That means you can essentially run a 2 for 1 sale on GW pots when you combine them with this.

When you thin your paint with just water it breaks it up and causes the body to fall apart sooner. I wrote an article a while back about what that means but basically, it's like the pigments coagulate and your paint turns microscopically grainy.

When your body falls apart it doesn't effect the solid coating very much but when you're trying to do multiple thin layers or airbrush it will matter and end up really looking terrible.

When you are doing thin layers you really want to thin it with this stuff because if you just thin it with water it'll end up turning into a wash. Instead, if you use the medium, it'll hold together but be like a very thin filter color. When people do light sourcing and get that illuminated look, they've thinned the paints down with matte medium to make their semi-opaque paints.

Flow Aid

The other must have for painting is flow aid. The design of this is to break up surface tension. Surface tension, for those of you more than 10 years out of high school is what causes water to "bead up. It causes water to basically want to be in a ball, like when you see the space videos of astronauts sucking down floating balls of tang. Greater surface tension means the fluid wants to be a sphere; Less surface tension means the fluid just splashes out were ever it wants to be.

Paint has a greater surface tension than water so when you brush on your paint, all that medium and pigments prevents it from setting smooth and that's why you get brush strokes. Flow aid, on a basic level, prevents brush strokes.

An important thing to know about flow aid is that unlike other mediums and additives, its in a concentrated form. You'll need to read the instructions on your own bottle but it's usually a 1:10 or 1:20 mixed with water. To help you guys that failed math, that means if you have a gallon of Flow Aid, that means you need to mix that in with 10 gallons of water, making a total of 11 gallons. This means, your 8 ounce bottle of Flow Aid will mix with 80 ounces of water to make 88 ounces of flow aid ready to mix. Flow Aid should last you forever...unless you're a commission painter....

Gess0 (pronounced Jesso)

Gesso is a primer used to prep canvas for acrylic painters. It works also with GW models. They make Gesso in black, white, and clear. Gesso can be brushed on in the most aggressive of fashions. If you youtube something about Gesso priming you'll eventually find videos of people just globing this shit on and it drying thin without obscuring any detail.

Clear Gesso can be mixed with any color to make a color primer. I haven't done this yet just because I still have a ton of black and white left. Where I'd start with experimenting with this is by mixing a fresh, unadulterated pot of GW paint 4:1 and work forward or backward on the ration from there.

As for using Gesso as primer I swing back and forth daily. I love it, I hate it. I think the happy middle ground I'm going to find for this is to use it for touching up scratches or mixed areas when I use a can spray.

The problem I come across with this is that it doesn't hold nearly as well as can primer. I've peeled this stuff off models with painters tape. It helps when you mix it with matte medium to give it a little more holding power but it'll still scratch off. Another tip to make it work better is to really do a good job cleaning your models.

The positives are that its cheap, lasts forever and can be sprayed out of an airbrush. Also, its not sensitive to the environment (humidity, temp, ect.) as the can primer is.

Slow Dry (or Fluid Retarder)

Slow dry is used, as the name suggests, to make paint dry slower. GW paint, if you spread it thin really does dry quickly. Do and experiment, spread a thin streak over plastic and see how long it takes to dry. It pretty quick.

This stuff gives you the chance to work with your paint for two things. One, it'll let you actually get an even coat. GW paint can dry so fast that if you're doing something like a shield or a sword, you dip enough paint to get half of it evenly, then you stop and dip again and by the time you get back to the sword the paint on it is half dry and when you stroke over it it globs up and then leaves a dry ring at the edges and just isn't smooth.

Slow dry just needs a few drops to really open up that working window. I'll add about 10 or so drops to a 1 oz bottle of my medium added GW paint. When I want to do a wet blend I'll add a drop to about 5 or 7 drops of paint. It doesn't make the paint wet for days, but gives you an extra 15 or 30 seconds of work time that'll let you push the colors back and forth like you want.

Glazing Medium

When I describe Glazing Medium to people I say its like anti-wash. The use of this is to create even layers and keeps paint from settling into cracks and recesses the way wash does.

On side effect I really like with this medium is the texture it gives when sprayed. I'll usually mix a really thin 4:1 layer of some darker color and spray the whole model when I'm done with all my airbrush highlighting. For example: I base coat dark angels green, high light snot green and then scorpion green, wash black, then glaze medium snot green. This helps seal the model and helps prevents that Gesso primer from coming up so easily as well.

Also, if you're looking to do OSL, this is a good product to pick up as well. You can do it with matte medium, but it might look better with this stuff since that's its design (thin layers). A good sample of the use of glaze medium is in Les Bursley's video where he paints the Nurgle Greater Demon from Ultra Forge. He uses it to add a slight purple color to low lights. I use it to make veins look like they're under the skin or scars or lips.


Windex is good for cutting GW paint for airbrush use. Liquitex sells an airbrush medium but I've never used it because Windex is cheap, readily available and works.

When I was searching for something to thin paint for an airbrush my goal was to just get something thin enough to spray at 20-30 psi and not clog up constantly. Adding water to paint just causes it to dry faster so whenever I was using that it just clogged constantly.

I've heard that windex causes paint to break down so I guess I wouldn't recommend thinning and storing your paint. Whenever I spray I will just mix the paint in the cup on my airbrush, meaning I drop the GW paint I added mediums to into my cup and then add about and equal amount of windex. and go to town. When I'm done I'll then just suck whatever is left in the cup back up into my little squeezy bottle. That means I do add a little bit of windex to my paint but I figure its such a small amount it won't matter. Hasn't yet.

Iridescent Medium

I bought some of this in hopes that it would be a super fine sheen kind of like when you look at gasoline in water and it has that rainbow kind of shine to it.

Its not. Its opaque glitter flakes. So, when that said, this is more of a warning of what this product isn't. If you wanted to make a red metal or a black metal then you can if you use this, but if you want to paint it on as a clear coat to make Tyranids look different then this isn't the product for you.

Matte Varnish

This varnish is about the best matte varnish I've used. I like it because its brush on so you're not totally screwed when the humidity is just off and now your mini is covered in fuzz.

It doesn't dry completely matte, but it is relatively matte to what some other varnishes that claim to be matte do but it still adds a shine to it, sadly.

Typically though, I'm fine not even adding a varnish to my mini. I've had more mini's ruined with varnish, than I've had saved by varnish.

High Gloss Varnish

As its name suggests, this is a very very high gloss varnish. I uses this when I need something to look wet or shinny. I use it on eye balls, teeth, monstrous creatures mouths, gems, lights, ect. Its a good tool to have to help you be lazy and not have to make something look like its reflecting.

Well readers, that's about all I know about mediums in a nut shell. I hope this article helps to clear up any questions about mediums and sparks you to go out and get some mediums and start having those terrible GW pots work for you instead of you pulling your hair out when using them and destroying your brushes.

As always, questions and comments are welcome!

Oh, and here: (they won't care about the expiration date...usually)


  1. Great article, man! Let me just add that Gesso also comes in Grey/Gray (depending what side of the lake you're on) and is my default primer.

    I airbrush it on (with a touch of windex, as well!) and what I love about it is the fact that it usually dries rather quickly. You can make grey with the white gesso, of course, but I figured I'd throw it out there.


  2. Genuinely useful post. I've not really explored the world of painting chemicals and this is a great prep article. I think I'll try some of the medium as that sounds like the most useful thing for me. Thinning GW paints is a must.

  3. Tremendous post. Thanks for the top tips. I've been standing in the shallow end on this for a long time for fear and inexperience. Your post goes a long way to helping rectify that. Cheers!

  4. Fantastic. I never have used any mediums in my paint, but I am definately going to start. The P3 paints I normally use are pretty god to go, but I am starting to use more of the GW paints too, and I agree that they are really thick (especially Astronomicon Grey...)

    Do you recommend using matte medium and flow-aid together, or just one or the other?

  5. Thanks for the comments, I appreciate the feed back and knowing that the article is really helping out.

    Stormloard- my paint ends up being 1/3 GW paint, 1/3 Matte, 1/3 Flow Aid. They're a little more thin than people might want in the end but basically what I do is dump the pot in the squeeze bottle, fill it with medium, stir it up, dump the pot in the bottle, fill the pot with flow aid water, shake, dump into the bottle whatever amount of the flow aid water will fit.

  6. Old School translating for Capt. Obvious: "Good Article CV. As for the Iredesent Medium. That is used for the iridesent paints. last hobby store i was in actually had a huge liquidex poster that broke down all their mediums. It said for the iridesent medium best used with iridesent paints. so im assume the oil paints...they had some there but were like $22 a small tube."

    Remeber guys, while I might throw a curse word around every once in a while, dropping bombs just to drop them here is a little unnecessary.

  7. ... and my turn ... great article CVinton. It hits home for me as I just started weilding the paint-hose and it really is intimidating at first just because there are so few resources and "pro-tips" out there specifically for dealing with our paints and our artistic subject.

    This is a great breakdown and I will probably print this so I can ready reference it as I start getting more familiar with the air-brush.

  8. Bookmarked! And to think that I've only just stopped taking paint straight from the pot... oy. Well, if I ever have the time to brush up my skills (it's a punne, or play on words...) DFG is definitely a mine of awesome content. Thanks!

  9. Thanks for the very helpful article. Although I've used Flow Aid, I was always nervous about using Gesso and the Mediums. Indeed, until now, I didn't have a clue about what they really did. Thanks again for posting this article and helping me save some time. Very greatly appreciated!!

  10. Nice read.
    It's good to see someone taking the time to go a little in-depth with some of the lesser used things.

    I'll be honest, it's paint and water for me these days, but I'm tempted to try my hand at some of these products in the future.

    Ron, From the Warp

  11. A great read - thank you.

    I'm sure I knew most of the products and info, but it was still good to see it all in one place.


  12. Excellent article. Right now I just use matte medium for mixing washes and thin my paints with a water/flow aid mix, and I definitely notice the breaking down that you mentioned. I have to constantly re-mix the paint to get it to work right. The matte medium seems a bit viscous for thinning paints though, do I really just add some matte medium by itself to thin my paints? Should I add some flow aid as well?

    I'm a big fan of priming with gesso because I can brush it on any time of day in any weather and I don't have a garage or any good place to spray prime. Just don't get Bob Ross brand gesso, it will dry fast and hard and ruin your minis with big blobs of gunk that you need chemicals to remove.

    I am looking into buying an airbrush and would LOVE to hear the recipes/methods that people use for airbrushing on gesso. It comes out of the bottle pretty thick, so it will obviously need to be thinned. Would I just add a bunch of Windex to it or is there some other way I should go about it?

    I've been experimenting with mixing the iridescent medium with acrylic artist's ink and it creates a very pigment-rich metallic color.

    I have stayed away from the liquitex varnishes because I read somewhere that they are not true varnishes. I don't know how accurate this is, but apparently when you apply a liquitex varnish it is PERMANENT - you can't strip it off to fix mistakes or make changes one it's on there. Can anyone else verify the accuracy of this?

    Again, excellent article and thanks in advance if anyone can answer my questions.

  13. Reflection of heat protects structures from wide temperature fluctuations, thereby reducing the thermal load to the structure. As the thermal load is lowered, air conditioners run more efficiently thus lowering energy costs. Is this true to all paint additive?

  14. Have you tried Testors dullcoat? You get it at Michaels the cheapest and it's all but idiot proof. It'll cover models super quickly, can go on thick, dries thin, clear, and matte. It's a super varnish imo.

  15. Good article. Very helpful. Thanks.

    It wasn't until my second reading that I got the Lexington Steele reference.

  16. I've hand-brushed on Gesso before but would definitely be interested if anyone has a "recipe" for airbrushing it on. Is Windex the thinner of choice with Gesso also? As noted above, Gesso is very thick.

  17. I found a recipe for airbrushing gesso that has been moderately successful. I have Liquitex brand gesso and they recommend a 2:1 ratio of their airbrush thinner to gesso. It has worked at least some of the time but other times I have trouble with it gumming up my airbrush. It might be a problem with the materials or the recipe but it's just as likely that I'm doing it wrong.

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