What is the difference between a single action and double action airbrush


When I first bought an airbrush I had my mind set on a double action airbrush just like everyone uses that I watched on YouTube and other places. I went into my local hobby store and talked to my friend behind the counter. We started to talk about the things that I wanted to paint, and what I wanted to do. It turned out that what I was trying to do would be better served by a single action airbrush. I will cover the differences and why in my particular case I chose to start with a single action airbrush instead if a double action airbrush.

The difference between a single and double action airbrush is the paint delivery mechanism. A single action airbrush delivers paint with only the press of a button. A double action airbrush only lets air pass through when you press down on the trigger. It begins to let paint through when you slide the trigger back and allows more through as you pull the trigger back further. This allows you to adjust the size of the paint stream, and amount of paint passing through your brush as you paint. The ability to do this is the primary advantage of a double action airbrush over a single action airbrush.

There are several other aspects of airbrushes that come into play as you use them. I will cover the differences in this article.

The picture above is of my Badger, single action, siphon feed, external mix, airbrush. It couldn’t be much more different from my Pache, double action, gravity feed, internal mix airbrush. I will go over the differences between them next.

Gravity feed vs Siphon feed

This describes the method of getting the paint from the paint cup to the mixing area. The two paint delivery methods make a difference when using your airbrush. Gravity feed is when you have a paint cup of some type on the top of your airbrush, The paint is pulled into the air stream of the brush primarily by gravity. In a siphon feed system, you have a paint cup that is below or to the side of the airbrush. Air passes over the tip of the paint tube and siphons the paint out of the paint pot against gravity. Many double action airbrushes are also gravity feed airbrushes, but there are single action gravity feed airbrushes available as well.

Internal Mix vs External Mix

I have personally not seen a gravity feed airbrush that is external mix. In a gravity feed airbrush, the paint is drawn down by gravity into the barrel of the airbrush. When it enters the barrel it mixes with the air passing through the airbrush while it is inside the airbrush itself. This mixture is then blown out the front of the brush onto your model.

Siphon feed airbrushes can be either internal or external mix. It is easy to tell which is which. If the siphon tube goes directly into the barrel of your airbrush then it is an internal mix airbrush. However if your airbrush is like my Badger 550 and the siphon tube goes into a needle that is held out in front of your airbrush, then it is external mix. This means that as the air passes over the tip of the needle it draws the paint up through the tube and then it is placed on the model that you are painting.

I find that I get a condition called dry tip more often with my external mix airbrush. Dry tip is when some of the paint coming out of the airbrush dries on the tip of the needle. When this happens it can block the paint as it comes out of the airbrush. This also seems to happen more when using water based paint like the acrylics that are most commonly used when painting miniatures.

Ease of Cleaning

Single action, external mix airbrushes are simple to clean. When I clean my Badger 550 there are only 6 pieces to keep track of, that is a lot simpler than my Pache Talon. When you disassemble a double action airbrush, there are many moving parts to keep track of. Don’t take this to mean that it is so difficult that it should discourage you, it just means that there are more parts. 

Adjust the amount of paint coming out

To adjust the amount of paint that is coming out of the airbrush it depends on the type of airbrush that you have. If you have a double action airbrush, then you can adjust the amount of paint by sliding back on the trigger. The further that you slide back on the trigger the more paint it allows to come out of the brush. The other aspect that is affected by  the trigger is the spray pattern. As you allow more paint to flow through the brush the spray pattern widens and the paint is disbursed over a larger area. This can be done at any time while painting.

To adjust a single action airbrush you need to turn a dial of some type in between air bursts going through the airbrush. On my Badger I need to turn the cone located at the front of the airbrush assembly that covers the needle. The more you loosen the nozzle the more it allows paint to flow through.

What is not a difference

You can get the same amount of detail from a single action airbrush as you can get from a double action airbrush. The size of dot that comes out of the brush is more of a function of the needle that you are using.

The vast majority of airbrushes can change the needle that regulates the paint and airflow. You can see the three different needles that I have for my badger airbrush. The high flow needle on the left is thicker and tapers drastically at the tip. The fine flow on the right is very gradually tapered. The differences in the needles makes the airbrush perform quite differently. large diameter needles change the flow of paint quickly coming out of the airbrush, they also let more paint come out. The fine needles change more gradually and have a smaller limit of paint that will come out when you use them.

Top airbrushes for painting miniatures

My recommendation to start with: single action Badger 350

More advanced airbrushes once you get the hang of it

Badger Patriot 105

Iwata Eclipse HP-CS

Badger Sotar 2020

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