We have a winner! I’ve been experimenting with different mediums to thin my gesso through an airbrush and I think I’ve got something that works.
I’m running this using Golden Artist Colors (Golden) black gesso. Airbrush tip is .3. 40 PSI/2.75 bar. I’d also let these dry at least 6 hours unless specified otherwise.
When I looked up the Golden Airbrush Medium to find out more about it, I noticed it talks about safe ratios to mix it with gesso! So apparently I didn’t think this up first (duh) and someone from Golden had figured out the ratios their products can handle each other. And that ratio is 2:1 medium to gesso.
Now that’s a much, much higher ratio than I had been doing, and explains why I was having issues with sputtering and clogging through my airbrush using gesso.
I must state: water is possible, but the risk of over-thinning your gesso to uselessness is too high. Golden gesso is only rated to 20% water-to-gesso, and that’s too low to get it through an airbrush. Higher than that and you’re going to wipe out the durability and it’s going to come off no matter how much you hope it won’t. So stick to mediums here. I’m going to review water anyway as a baseline.
I’m going to note, too, I haven’t been using these for very long as I just discovered how to do this. I can’t attest to long-term performance. But considering all of these are acrylic mediums on an acrylic gesso, I’d imagine it’d hold up like an acrylic paint.
I’ll be giving these a rating based on flow, durability, sheen, paintability, and “primes the airbrush.” The last one is how hard the gesso tries to prime the inside of your airbrush, which is bad for cleaning but I’ve found to be somewhat indicative of durability.
Water
I’m doing this one as a baseline for airbrush priming with gesso since it’s what I started with and shows the worst option. You can’t add enough to get flow and it results in a lower overall durability. Painting surface looks nice but isn’t really usable. Just sad.
I suspect, even at 20% water, the durability is also lost because of the aerosolization properties of going through an airbrush. The paint isn’t sticking together in the globs it needs when running as normal brushed-on gesso because it’s been thinned out so much. You’re basically spraying on pigment that’s lost much of its priming properties.
And even after all that it still clogs and refuses to come out of the brush. So good luck cleaning that.
Rating: Rating (out of 5, 5 highest): Flow: 1; Durability: 1; Sheen: 3; Paintability: 1; Primes the airbrush: 5.
Vallejo Airbrush Thinner
The Vallejo Airbrush Thinner is something most miniature painters are familiar with and will have access to. This stuff is great because it thins without fundamentally changing the gesso itself, and I found once you added in the appropriate 2:1 thinner-to-gesso ratio, the end result was a very nice and very thin primer that flowed very well.
I found though this stuff wasn’t priming the inside of the airbrush at all. This made me a little concerned as the goal of using mediums was to prevent over-thinning, and it wasn’t acting quite right. Gesso will stick anywhere, no matter what, and this change indicated it would lose durability.
The gesso/Vallejo mix came out of the airbrush as easily as any thinned paint though and stuck to the model fine. My initial impressions were this was the best option, as it just plain cleaned up well, stayed on and (once dry) looked almost exactly like regular dried gesso, with an almost unbelievably matte finish.
But after a bit I found it could come off easier than the other two main options. It had lost durability somewhere that was disappointing. This affected the paintability score, since it was a little too soft. I don’t think though that it affects the paintability that much, but I consider durability to be important to how secure I feel blending on the model. If it’s too soft, I get nervous.
Rating (out of 5, 5 highest): Flow: 5; Durability: 2; Sheen: 5; Paintability: 3; Primes the airbrush: 1.
Golden Airbrush Medium
Golden Airbrush Medium is Golden’s answer to airbrush thinner. It has many, many more properties related to being a medium than just thinner, and I think this makes it a powerful, powerful option for anyone looking for a magic mixture without wishing to gather all the pieces of Vince Vinturella’s special blend. (I can’t find the link to this at the moment.)
This stuff’s product page talks about the ability to thin certain paints, and when I saw the entry for gesso I got the idea to use it.
Overall the result is pretty durable and quite attractive. It flows great and sprays very well. I really liked it, but I found that for some reason it had a few spots that the paint just wouldn’t adhere. This may be particular to plastics, but there’s something there that limits the durability and it’s only in particular locations. I may have touched it while it was drying and messed something up or something, but this was a downer.
Additionally, it takes a VERY long time to dry. I’d give it at least 12 hours and be very careful not to touch it. I don’t see any retarding properties in the medium’s description, so I don’t know why that is. Until it dries all the way it is extremely sensitive.
Once dry though, and if it adheres right, it’s quite awesome. Thin, beautiful on its own and both satin and matte somehow. An absolutely perfect primer if you don’t get any of those soft spots.
Rating (out of 5, 5 highest): Flow: 5; Durability: 3; Sheen: 5; Paintability: 4; Primes the airbrush: 4.
Golden High Flow Medium
Golden High Flow paints are their almost-inks that work especially well in airbrushes and have the best fluorescents on the market.
Perhaps then as a result, Golden High Flow Medium is my winner. Despite the name, this stuff is a great airbrush thinner. It’s designed to bring heavy body paints down to high flow properties for airbrushing, and it excels in that in every way. It only makes sense that it would be able to handle gesso, too, which is highly pigmented and viscous. I use this stuff as a general medium as well because it can be so useful as an alternative to water or thicker paint mediums.
Additionally, High Flow Medium contains durability enhancers. So you’re also basically enhancing the strength of the paint by using it. This solves the main problem I’ve found with airbrushing gesso entirely, and probably the reason it wins out so well.
The main drawback is it can be quite glossy before it dries completely. But because gesso is so matte by nature, these can balance out and produce a satin surface that still paints quite well with good tooth. The real question is if the satin surface really bothers you. I’ve found it has no effect on my painting and the extreme quality of the prime makes it worth it.
I’d rate this primer as better than polyurethane in all areas and, thanks to its less finicky nature, even better than rattlecans. The only real downside is it has to be manually mixed as no one’s figured out miniature painters might want this stuff for themselves.
If I were Monument Hobbies, Reaper or Army Painter, I’d call up Golden and contract getting this put together in a stable solution for resale. It is, in my opinion, quite magical. And since it’s still acrylic, it’s less toxic and can be removed with normal acrylic stripping methods. What’s not to love?
Rating (out of 5, 5 highest): Flow: 5; Durability: 5; Sheen: 4; Paintability: 5; Primes the airbrush: 4.