There are different tools for working with paint. The airbrush —also incorrectly called airbrush– is a tool which works on the basis of a stream of compressed air which, due to the principle of venturi tube, atomizes the liquid contained in a tank for this purpose; thus, the liquid (which can be painting but also oil and others) is atomized and can be applied uniformly on any surface, thus achieving great neatness and finish.
Although there are paint guns that work based on other drive methods (electromechanical for example), in this note we will see the pneumatic ones, powered by compressed air.
How is a paint gun?
Is a tool that projects atomized paint, under pressure, through different interchangeable nozzles. It consists of a body -generally metallic-, a trigger, a nozzle where the mouthpiece is screwed on, a container to place the painting, and a hose for compressed air. Some advanced models include a pressure gauge to know the air pressure.
Pressing the trigger opens an internal valve that regulates the entry of the compressed air (and its flow) thus allowing to regulate the output speed of the paint, and its quantity.
What is the difference between a paint gun and an airbrush?
Although the operating principle is identical in both tools, the Paint guns They are prepared to receive a pressure greater than that required in airbrushes.
The airbrushes They are designed to carry out artistic work, so they are smaller and have an elongated shape, similar to that of a pen. The Paint guns, designed to perform more intensive work, have a pistol shape, which makes them more anatomical.
How many types are there?
There are two main types of technology to achieve paint atomization: by air current (pneumatic) and by generation of an electrostatic field. There are also other types, as we will see a little later.
Pneumatic paint guns
The paint guns pneumatics are classified according to the pressure and volume they handle, although it is very rare to find a airbrush to work in a high pressure regime, since it would waste a large amount of painting when it remains suspended in the atmosphere (something that also causes serious health problems).
Are pistols require the use of an air compressor with a reservoir in order to use them; in some cases the same tool It includes a compressor specially designed to deliver the air at the necessary working pressure, which makes the tank unnecessary.
In the classification by volume there are two main categories: HVLP and LVLP. In both cases, to qualify as such, the pressure must not exceed 690 hPa (approximately 10 psi).
Classification by volume of paint per minute
They stand for High Volume, Low Pressure. The gun, working at low pressure, allows to apply a high volume of painting, which implies a higher flow rate (around 2.9 cubic meters per minute) and, therefore, a higher consumption.
The advantage of this type of paint guns is that they allow painting a given area in less time than the use of LVLP guns would require, although the consumption will be a little higher. They are especially useful for large workshops, where production speed is more important than consumption.
In this case, the acronyms mean Low Volume, Low Pressure, and those that work with pressures no greater than 690 hPa (10 psi) and develop a flow rate no greater than 2.9 are classified as such. cubic meters per minute.
This type of spray guns They allow you to save paint by sacrificing work speed. They are indicated for home or workshop work with modest production requirements.
Classification by the position of the paint tank
Another important factor is the location of the deposit of the painting. Some models, as we saw before, work by venturi’s principle: the passage of air through a tube placed perpendicular to another causes a vacuum in the latter, thus dragging the liquid contained below, atomizing it at the nozzle outlet.
In the models whose deposit is above the nozzle, the paint descends due to the action of gravity. Are paint guns they are used when the paint is too viscous to be vacuumed.
Electrostatic paint guns
Are spray guns achieve atomization by a different principle than the venturi tube: Inside a piston, the paint drops are electrically charged, thus repelling each other. This allows them to come out evenly through the nozzle when compressed air is applied.
Some models completely dispense with pressurized air, achieving the output of the painting by means of a cylinder that offers pressure to the liquid, pushing it through the nozzle; the paint, electrically charged, causes the drops to be separated.
This type of spray guns —mainly used in heavy industry such as shipbuilding— use a piston to strongly compress the paint and force it out of the nozzles, where atomization occurs. The painting It comes out pressurized, without the need to use compressed air to propel it. This allows better adherence, especially on uneven surfaces.
They are integral systems in which the painting It is applied inside a sealed and pressurized chamber. The greatest use of this application is in the automotive industry, where it is extremely important that the finish is perfect and durable.
Although technically they are not considered as paint guns (because they take up practically the space of a small garage), we include them here for comparison.
Automated production lines
In these systems the airbrush It is operated by a fully automated system, without the need for an operator to apply the paint manually. Its use occurs exclusively in medium and high production factories, where it is extremely important to control the homogeneity and economy of the process as much as possible.
Just as important as the position of the reservoir is the shape of the nozzle used to apply the paint. In the photograph above we can see the three most common.