The air pressure of an airbrush plays a big role in how you paint and what final results you will get. The airbrush pressure is generally measured in pounds per square inch or PSI for short.
Understanding and using the appropriate PSI is likely going to be different from one user to the next. It can also vary from one custom paint job to another.
The pressure depends on multiple factors such as the type of airbrush, viscosity of the material you intend to spray, and the surface area on which you will apply the paint.
This article provides a detailed guide on how airbrush pressure works and how you can use it for various painting projects.
Airbrush Pressure Details
How Do Airbrushes Work?
Airbrushes work on the simple and common technique that you may have seen in any other household spray. When you press the nozzle, the spray pulls paint from the paint can and forces it out from a pinhole opening.
The pressure developed by the system forces paints to break up into many tiny droplets, uncovering a process called “atomization,” which controls the size of the paint particles.
What Does Airbrush Pressure Control?
The question is, how does airbrush pressure play a role in this?
You have probably seen something similar to an airbrush with your garden hose, when you wash your car or water the lawn. When water is supplied to the hose, the mouth opens up, and a water jet gets squeezed through the nozzle.
If you allow the hose’s mouth to open only slightly, it results in a fine mist as only a small amount of flowing water is put under a high degree of pressure.
But if you keep the water pressure at the same level but fully open the hose, it allows the water to flow freely. The high pressure propels the water to a greater distance because it is a steady stream instead of being atomized into fine droplets.
By controlling the size of the opening, you can control the size of the droplets. Controlling the water pressure to the hose means you control how far the water jet can go.
In an airbrush, air pressure is supplied to the nozzle from an attached hose. The paint and air meet right in front of a tapered point called the needle.
Needle size determines the size of the droplet. You can control the air pressure, which is measured in PSI, from a compressor. Managing this combination is the most difficult aspect of spraying and something that you will only learn with experience.
Effects of Paint Viscosity
The pressure that you can build with an airbrush is also affected by the paint viscosity. Thinner paint is easier to atomize even at a lower pressure. If the paint is thicker, it requires much greater pressure to atomize.
For most professionals, air pressure and thinned paint go hand in hand. If you thin the paint, you must lower the air pressure to get the ideal effect. Generally, it will require some experimenting to find the right concentration.
The Quality of the Airbrush
Airbrushes come in different qualities and a variety of materials. Higher quality airbrushes do a much finer job of atomizing paint even at a lower pressure compared.
A low-quality airbrush will not be sensitive or responsive enough to react to the subtleties of air pressures.
Airbrush kits are available in price points of uber-budget to professional quality
If you are looking to use an airbrush for professional jobs and need to atomize the paint at the lowest pressure possible, then you’ll need to buy a higher quality airbrush that will have this built-in.
Quality of engineering materials and manufacture really makes a difference in an airbrush! You’ll find our recommendations for the best airbrush here.
Even if you are only painting as a hobby, we advise avoiding the cheap airbrushes and buy tried and tested brands that are more expensive but deliver better results.
For an in-depth review and recommendation of airbrush kits, the best airbrush here.
Nozzle and Needle Sizes
Most of the commercial-grade airbrush nozzles and needles are made of plastic. They range between 0.2 mm and 0.5 mm, with 0.35 mm being the middle ground.
Going back to our previous water hose example, when you open the hose only slightly, even a low pressure can give you the desired jet of water. If you increase the pressure while keeping the opening small, it puts unnecessary pressure on the nozzle.
The same rule applies to airbrushes. A brush with a small nozzle and needle size can work well with lower air pressure. Airbrushes with a large needle size or nozzle will need higher air pressure to atomize paint effectively.
So if you are using a 0.2 mm nozzle, the airbrush pressure will need to be lowered substantially compared to using a 0.5 mm nozzle to raise the pressure airbrush pressure to get a similar effect.
It is worth noting here that small brush sizes of 0.2 mm will work better with thinner paints. With a nozzle of 0.5 mm, you can work with both thin and viscous paint.
If you are especially interested in airbrushing fine details, you will appreciate an airbrush for that specific purpose. You can read our examination article on airbrushes for miniature works here.
Airbrush Feed Styles
Airbrush feed style plays a role in how much pressure you need to spray. The 3 most common feed styles you can use include the following.
- Gravity Feed Airbrush
- Side Feed Airbrush
- Siphon Feed Airbrush
The feeding mechanism of your airbrush determines how much air pressure is required to get the paint into the atomization chamber of the airbrush.
Gravity airbrush feeding styles require a lower PSI to work correctly as it uses the force of gravity to push the paint into the nozzle. The siphon feeding style requires more pressure as it is working opposite to the force of gravity.
Side feed mechanisms are a mix between the two opposing styles and are less common. It places the paint cup at the side of the airbrush.
The common PSI ranges for each airbrush feed mechanism are illustrated below.
PSI for Siphon Feed Airbrush
The most commonly used air pressure (PSI) for a Siphon feed airbrush is around 25 PSI – 80 PSI based on the viscosity of the paint being sprayed.
PSI for Gravity Feed Airbrush
The most commonly used air pressure (PSI) for a Gravity feed airbrush is around 12 PSI – 45 PSI, and is affected by the viscosity of the material being used.
PSI for Side Feed Airbrush
The most commonly used air pressure (PSI) for a Side feed airbrush is around 12 PSI – 45 PSI, and depends on the viscosity of the paint being used.
Finding the Ideal Airbrush Pressure
Many new painters believe that there is an ideal airbrush pressure that you can achieve to get good results. That is not true.
Actually, there is no exact pressure in PSI for use in all situations. You will need to adjust it from time to time to get the results you want.
Think of the above example of using a water hose to wash your car. If you lower the pressure and open the nozzle only a little, you will get a very mist-like spray that will take a long time to wash your car.
Keeping the pressure low and opening the nozzle wide will get a weak water jet that may not reach the surface of your object.
If you raise the pressure high but get too close to the vehicle, the water jet will bounce from the car and back onto your clothes, making you wet.
Working with an airbrush works in a similar way.
When you hold the spray close to the surface, you will need to lower the pressure to prevent overspray. If you are standing at a distance from the surface, you will need to apply more pressure just to connect the paint to the surface of the model.
Small particles of paint do not drop like water a stream. Instead, they disperse through the air in the direction where you point your airbrush, until they land on a surface.
If the paint has to travel a good distance through the air it will dry, or partially dry, by the time it hits the models from the airbrush. Therefore, it may not give a smooth look but create more of a dimple-like effect on the paint surface.
Factors That Affect Airbrush Pressure Recap
To recap, here are the main factors that affect the airbrush pressure.
- The Overall Quality Of The Airbrush
- The Feeding Mechanism Used In The Airbrush
- Whether Your Airbrush Is An Internal Or External Mix Airbrush
- The Size Of The Airbrush Nozzle And Needle
- The Type Of Material You Will Use And Its Viscosity
- The Distance OF The Nozzle From The Surface You Are Spraying
- The Type OF Surface You Are Painting And The Project
As you can see, there are many variable factors that affect the airbrush pressure that you need for spray painting. You will need to test out the ideal pressure with different types of paints and airbrushes that you use to get the right results.
The good thing is that you only need to do it once for each paint type. You can make a note as you work to find the right pressures. Once you have them figured out, you can use the same air pressure setting for future projects.
Also, when you have figured out the best combination, it will become easier to make changes to different types of paints. You will also learn how to adjust different airbrushes to your requirements using the same type of paint viscosity as well