Hello all,

Would anyone happen to have an idea of a rough dilution ratio for Vallejo model air for fine details and free-hand camo? Any recommended psi?

Using a dual action AB with 0.35 mm needle.

Thanks!

I think Vallejo recommends you limit thinning to 1 drop thinner to 3 drops paint using their airbrush thinner. Hope this helps.

Paul H

Hi Paul,

Is this a regular dilution or for lower PSI? For normal painting I usually either use neat model air with a drop of flow aid or 1-2 drops thinner on 15-20 drops paint (approx). This is sprayed at 20 PSI running (25 preset).

If the constitution of the paint is supposed to be "milk-like" on average, how is it diluted for low PSI precision work?

For handbrushing use the white Vallejo thinner instead of the airbrush thinner. The airbrush thinner is a much more aggressive substance that might ruin earlier paint coats.

I use the white Vallejo thinner about 1 part thinner to 4-5 parts (drops) paint. Using retarder is not essential for camo painting.

Hi,

there's a quite simple logic behind the decisions you have to make about the air pressure and the dilution of the paint/thinner mixture.

It's obvious that fine details require much more precision and control in applying the paint. Thus, you should be able to apply very light, semi-transparent coats of paint - to control the desired effect to avoid the risk of flooding the model with excessive paint.

This leads us to 2 conclusions:

1. For semi-transparent coats you need to thin the paint significantly more than for the base coat.

How much more? As much as you can, but you have to be careful to avoid turning thinned paint into colored thinner.

For Vallejo Model Air it means at least 1:1 ratio between the paint and Vallejo Airbrush Thinner.

And then you have to check the mixture - it should have no visible "viscosity" at all, flowing as easy as water (this might be not 100% precise description terminology-wise, but I hope you' understand what I mean). And feel free to add more thinner - but, again, watch carefully not to cross that "magic border" when "thinned paint" turns into a "slightly colored thinner".

2. Pressure-wise you need to maintain the balance between creating enough air "suction" at the tip of the airbrush to have the paint pulled by the Bernoulli effect, and, at the same time, to avoid having so much pressure that you'd lose control of the painting process.

1.2-1.3 bar (17 - 19 psi) should be a good starting point. But I wouldn't go over 20 psi and lower than 15-16 psi.

The thinking ratio I gave you 1 to 3 comes from Vallejo. They believe the paint is already thinned enough for standard spraying. For people with larger tip "general modeling" airbrushes the out of bottle mix is fine. For those who have adopted airbrushes with smaller tipped "detail" brushes they will need to thin more for good performance.

A word of caution... acrylic paints start to lose adhesion when thinned too far. They cease being paint and become more like stains and tints. As long as there is a primer or a flat base coat you'll still be able to pull off whatever you need with very thin paint. If not, over-thinned paint will not adhere to the plastic well at all.

Your painting methods dictate how much pressure is right, as does the construction of your airbrush. For the most part, fixed nozzle internal mix brushes like the Iwata HP-B take less pressure to atomize paints than the self centering cone type like the Iwata Eclipse series. New detail brushes like the Badger Renegade series or the Harder Steenbeck Infinity series don't follow this example but it's still a good general rule.

The best way to determine what is the best pressure for your work is to look for the thinning ratio and pressure that give good atomization and the smallest amount of overspray (the paint that is outside the intended pattern) while producing a wet coat of paint.

Just a word of caution - DO NOT attempt to paint with water-based acrylics (Vallejo Model Air, AMMO of Mig, AK Interactive, etc.) in the way you would have applied a traditional solvent-based paint (lacquer or enamel).

The core problem is that with water-based acrylics each subsequent layer does not partially dissolve the previous layer (thus leveling the whole combined set of layers).

Thus, water-based acrylics need to be applied in very thin, semi-transparent, nearly dry layers + the next layer can be applied only when the previous one is dry. Otherwise there's a HUGE risk of getting very undesired side effects.

The guys at AMMO of Mig even did a video on this: https://www.youtube.com/watch?v=yZHAqxSHHvc (start watching at 2:07).

There is a balance to thinning, lowering the pressure and distance to the surface you are trying to apply the paint. This balance depends on a few things as well....environmental conditions, AB used (tip and needle included) and individual applying the coverage.

With that said, a base line for thinning Vallejo's Model Air is 1 drop for every 4 to 5 drop of paint. I recommend a pressure of between 12 to 15 psi. The more detailed you want to get, you will want to get closer meaning you will need to lower the pressure, thus wanting to thin the paint more.

You mentioned having a 3.5 needle on your AB. There are some limitations to details with a tip this size, however, you should be able to handle any camo job and singling out minor details as needed.

For starters, I would give 2 drps of thinner to 5 drops of paint. Lower the pressure to between 10 and 12 psi. and test. If he paint comes out fine without spitting, lower the pressure slowly until you experience spitting. This will give you a good reference of where this mix can shoot too. I have been successful in taking a thinned mix down to between 6 and 8 psi and still have coverage. The mix is thiner and will need another one or two coats, but will apply and once cured, will not come off. Most instances of Vallejo paint coming off is from not allowing for a full cure of the paint...12 to 24 hours...or from to heavy of an application, which subsequently results in longer cure times.

The application will always work better building up your application in lighter coats until your are happy with the finish. With Model Air, typically you do not need to do this as the paint is proportioned to shoot right out of the bottle. But when thinning, this is the best practice.

Best of luck!!

This limit can be stretched by adding an extender. Liquitex airbrush medium works for me, and extends the limit where thinning will break the paint film. I've read that other have thinned with Future as well, which probably would have the same effect.
What it does is adding binder to the paint, without adding any pigment.

Gentlemen, thank you for the replies!

Phil, you said that acrylics will tend to pile on top of one another rather than partially dissolve into the underlying layer. It makes sense. I painted my model with vallejo model air over vallejo primer. Each later was allowed to dry in excess of 4-6 days.

Do you thnk it would be safe to mask with tamiya tape and then spray very thin layers of model air, allowing them to partially dry before making the colors opaque?

Thanks!

I think this is exactly how Model Air is meant to be used Please check this video - https://www.youtube.com/watch?v=yZHAqxSHHvc (start watching at 2:07) - I am sure you will find it very useful.