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Spray painting provides a much more controlled and uniform finish on your paint job than any hand-applied roller/ brush job. However, investing in the best spray gun and air compressor for car painting doesn’t guarantee you’ll get optimal results immediately.
At least not until you learn how to set up the perfect pressure for your spray gun.
Generally speaking, running a spray gun off a compressor gives you an infinite range of pressure to use. Unfortunately, if you apply too little pressure, you’ll not get the best atomization, causing the orange peel effect on your car paint.
On the other hand, if you apply too much pressure, you’ll end up wasting material due to excessive bounce-back/ overspray.
Don’t worry though! In this article, I’ll walk you through everything you need to know about setting up the right spray gun pressure for your project. This will help you produce less overspray and allow a quick clean-up, saving you both time and money.
Why Spray Gun Pressure is Important
First of all, the air pressure of a spray gun affects how the coating is atomized and propelled out of the device onto the target surface. In short, this is what makes the spray gun deliver a flawless finish at a fast speed compared to traditional brushes and rollers.
Most types of spray guns, whether pneumatic, airless or turbine, are equipped with an air pressure regulator. This allows you to increase or reduce the pressure of the spray gun depending on the type of coating you’re spraying and the size of your painting project.
In that regard, thicker coatings and large surfaces require a higher spray gun pressure. While spraying thinner material like applying a stain to a small object will need less pressure.
What’s the best pressure for spray painting?
Different types of spray guns use slightly different technology to create pressure for atomizing the material you’re spraying and propelling it out of the device. Therefore, the ideal pressure for spray painting tends to vary from one type of spray gun to another.
In this section, we’ll look at the best pressure for each type of spray gun one by one!
Pneumatic Spray Guns
Sometimes referred to as conventional paint sprayers, pneumatic sprayers are powered by an external air compressor and can be classified into 2 categories, LVLP and HVLP. HVLP is an acronym for High Volume Low Pressure, while LVLP stands for Low Volume Low Pressure spray guns.
To be precise, here’s how pneumatic spray guns work:
An air compressor takes ambient air, pressurizes it and then forces the pressurized air into a tank to allow the pressure to build up. This air is then fed to an HVLP or LVLP spray gun through a regulator, adjusting the final pressure output at the fluid tip/ nozzle.
However, despite being driven by the same method, both systems have very different applications, and therefore, require different pressure inputs to deliver the desired finish.
LVLP (Low Volume Low Pressure) Spray Gun
Most professionals recommend setting an LVLP spray gun at a pressure of about 10 – 15 PSI when you pull the trigger to apply a base coat and 20 – 25 PSI for the clear coat. In addition, most LVLP sprayers have a CFM consumption of about 5 to 7 Cubic Feet per Minute (CFM) at 40 Psi.
HVLP (High Volume Low Pressure) Spray guns
As the name implies, HVLP sprays use a high volume of air at low air pressure. This pressure is usually 25% or less than that of traditional methods to atomize the paint coatings. As a result, the sprayed material has less velocity.
Thus reducing its chances to ‘bounce back’ and increasing the paint’s transfer efficiency. In addition, this method reduces material waste as it delivers a much softer spray.
However, HVLP spray guns demand a higher air volume than conventional spray guns, so you’ll need a bigger air compressor.
HVLP spray guns require a pressure of about 25 – 30 PSI when spraying two-stage (base coat clear coat) paint finish systems. To measure this pressure, pull the trigger and let air flow through the sprayer nozzle tip until the digital readout or dial reads 25 – 30 PSI.
However, sometimes you can increase the pressure of the spray gun to 40 PSI when higher atomization is needed.
Turbine Spray Guns
A turbine spray gun is a form of High-Volume Low Pressure (HVLP) device. They’re quite popular for most home-improvement coatings since they operate at relatively low pressure, reducing the amount of bounce-back.
However, unlike pneumatic sprayers, these spray guns are equipped with a stand-alone or integrated fan and motor system. Thus eliminating the need for an external air compressor.
The motor drives the small compression fans (otherwise referred to as stages) at high speed. In that regard, a spray gun with 2-stage turbine shows that it has 2 compressor fans.
The number of stages or fans in a turbine spray gun directly correlates to its overall airflow and pressure output. Therefore, 3-stage turbines are ideal for handling most water-based coatings, while single-stage models are suitable for applying less viscous coatings.
Regarding pressure, most turbine sprayers operate at a maximum pressure output of about 5 – 10 PSI, making them ideal for DIYers who have a wide range of painting tasks.
Airless Spray Guns
Airless paint spray guns are powered by a hydraulic pump and can generate an impressive pressure of over 3000 PSI. A motor drives the hydraulic pump, allowing it to atomize the paint internally.
More importantly, this allows the coating to hold the pressure before it’s forced through the fluid nozzle. In return, this creates an extremely high-pressure range that is completely adjustable.
Moreover, this allows airless spray guns to handle high-density coatings at a rapid pace, making them a popular choice for contractors with many commercial, industrial, and residential projects lined up.
That said, here are a few ideal pressure ranges for certain airless spray gun applications;
- Over 2000 PSI for latex paints
- 1200 – 1800 PSI for low-viscosity stains
- 800 – 1100 PSI for lacquer coatings
How to determine the ideal pressure for a spray gun
Some spray gun and car paint finish manufacturers recommend an ideal air pressure for spray painting. Although this may work just fine for you, there are several factors manufacturers can’t take into consideration.
This includes; the length of the air hose, the actual finish/stain you are spraying, temperature variations, and the amount of thinner you have added to the paint.
Moreover, they don’t specify whether the pressure is measured at the spray gun’s inlet, air cap, or at the compressor’s regulator. Yet you need an air gauge that attaches to the air cap or inlet if you want to adjust the pressure at these locations.
For instance, if the recommended pressure is measured at the air cap, you’ll need a special cap attachment with a gauge, costing you an extra amount of money.
On the bright side, you don’t have to rely on the manufacturer’s recommendations or on these gauges. Instead, you can easily find the ideal pressure for your spray gun using the following simple test!
Finding the optimum air pressure for your pressure gun
First, open all the spray gun controls to the maximum and turn the air pressure at the regulator to where you think it should be, such as to 20 PSI. Next, spray a short burst of paint onto cardboard or brown paper.
In most cases, this produces a relatively narrow-width pattern with large dots around the edges.
Now, increase the pressure by 5/10 PSI and spray another burst of paint onto the brown paper. Here, you’ll notice that the paint is a little wider, while the dots are a little smaller.
Continue raising the air pressure in 5/ 10 PSI increments and spraying short bursts. As you increase the pressure, the pattern gets wider while the dots at the edges become smaller. Make sure you hold the sprayer at the same distance (about 8”) from the brown paper/ cardboard for each burst.
Optimum air pressure
Once you reach a pressure that doesn’t produce a wider pattern or make the dots at the edges smaller, you’ve achieved the best atomization but you’re wasting material.
So, minimize the pressure to the previous setting since that’s the optimum pressure setting for the viscosity of the paint you’re spraying in the existing weather conditions.
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Interestingly, you don’t have to test the air pressure each time you spray, provided the weather conditions and viscosity remain the same. Instead, you can simply set the pressure at the regulator and you’re good to go.
However, if the temperature changes, use a different finish material or thin it differently, you will need to find the optimum pressure again! More importantly, this test will not work with turbine-air-supplied spray guns since you don’t have the same air pressure control.
Knowing how to set up the pressure for your spray gun will give you more flexibility depending on the project size and density of the coatings you’re spraying.
For that reason, it’s important to determine if the pressure output is appropriate for your project size, regardless of the type of spray gun you’re using.
More importantly, you should set up the gun every time you use it depending on factors like temperature and humidity as this will affect how you spray paint that day!
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