Painting, staining and other finishing projects can be time-consuming jobs. By the time your project is ready to paint or stain, you’ve likely already invested considerable time and resources in preparation and materials.
A spray gun, also called pneumatic spray guns or air sprayers, can help you get a job done faster — while delivering the high-quality results you’re looking for, whether you’re a DIYer or a professional.
So why should you consider a spray gun, and what type of spray gun should you look for?
Spray gun advantages
Spray guns offer several advantages over traditional painting or staining methods.
- Spray finishes are forgiving. Because a spray finish is built up in thin layers, small scratches and blemishes are not as obvious as they would be with a brush finish.
- Spraying is fast. Finish can be sprayed on pieces of any size or shape much faster than can be done with a brush or rag. In addition, atomization of paint or stain reduces drying time, so you can sand and recoat projects in less time. And because the finish dries faster, dust particles have less time to settle on the finished piece.
- Spraying is versatile. Nearly any finish that can be applied with a brush or rag can be replicated with a spray gun, but not all spray finishes can be done with a brush. Some finishes — such as lacquers and many water-based products — should only be sprayed. A spray gun also lets you use special techniques such as shading or toning that are much harder to do by hand.
- Spraying gives you greater control. You can control the rate of application and thickness of the coats much better with a spray gun compared to with a brush or rag. With an air sprayer, you can adjust air pressure, fluid flow and fan size to ensure you’re applying light and even coats over the entire surface of the workpiece. A spray gun also makes it easier to get into smaller areas or tight corners that can be difficult to reach with a brush.
- Spraying is easy. While it may seem daunting, using a spray gun is actually not hard to master. Often you can achieve proficiency with a spray gun much faster than you can with a brush.
- Spraying offers quality and consistency. Without a doubt, one of the best reasons to invest in a spray system is because of the quality of the finish. Brush or roller marks are no longer a problem. Issues with runs, drips, sags and trapped air bubbles are greatly reduced or even eliminated. When properly set up, used and maintained, a sprayer system delivers a smooth, high-quality and durable finish in a fraction of the time compared to a brush.
Choosing a pneumatic spray gun
Different spray guns are designed to suit different applications and materials being sprayed. Every setup has three essential components: a gun, which sprays the finish; a cup or pot, which holds the finish; and a power system, which moves the finish through the gun and atomizes it at the air cap.
Although there are many types of guns, their operation is basically the same. They contain inlets for air and fluid, a fluid needle, tip, and an air cap. The air from the air compressor enters through the hose and into the gun handle. Fluid enters the gun near the front, either from a cup mounted directly to the gun or from a remote pressure pot. A screw on the back of the gun adjusts the amount of fluid passing through the tip. Another screw adjusts the air passing through the air cap, controlling the fan pattern.
A spray gun must have a container for holding the spray material. These containers, ranging from an 8-ounce cup to a 10-gallon pressure pot, can be located below, above or away from the gun. The location of the container will determine how the material is fed into the gun.
Pneumatic spray guns utilize an air compressor to move and atomize the material. Depending on the spray gun selected, this compressor should deliver between 3 and 12 standard cubic feet per minute (scfm) at 40 pounds per square inch (psi). Most 5 to 6 horsepower units are adequate, and it’s recommended to use an air compressor that is 8 gallons or larger.
Most spray guns operate between 30 and 80 psi. It’s important to always be aware of the maximum air pressure. Failure to regulate the air pressure under the maximum rating can cause damage to the gun.
Spray guns come in many styles, including general purpose, pressure-feed, siphon-feed, gravity-feed and detail. The right choice depends on the type and viscosity of material you will be spraying, your range of painting tasks, your finish requirements and cost.
- General purpose spray guns are adaptable to a wide range of applications, and most can be converted from siphone-feed to pressure-feed. This allows a range of material to be sprayed — from stains to latex. They can further be converted from non-bleeder to bleeder style. Non-bleed guns shut off the airflow when the trigger is released, which is the best and most common practice.
- Pressure-feed guns use air to pressurize the material container, forcing fluid to the tip of the gun where it is atomized by air passing through the air cap. Pressure-feed systems must be tightly sealed to work properly. Pressure-feed guns offer several advantages over other designs: Material pressure can be regulated to move fluid to the gun, allowing thick or heavy materials to be sprayed, and air pressure at the tip can be adjusted independent of fluid pressure, so material can be applied at a much faster rate.
- Siphon-feed guns include a material container located below the gun. Compressed air enters the inlet and moves through the gun to create a vacuum at the air cap. The lid has a vent hole that allows air to enter the cup. The different in pressure between the air leaving the gun at the tip and air entering the vent hole creates a siphon that draws material up the fluid tube. The material is then drawn through the fluid tip, where it mixes with the air coming from the cap and is atomized. This style of gun is not as efficient when spraying heavier materials. Siphon-feed guns should be used with low to medium viscosity materials such as dyes, stains, acrylics and enamels.
- Gravity-feed guns operate similar to siphon-feed guns, except the material canister is located above the gun. This allows gravity to assist the fluid when entering the gun, creating a positive fluid pressure. This is important when using reduced gun pressures such as those in HVLP equipment, and also allows slightly heavier material to be sprayed. Better gun performance and significant material cost savings are benefits of this type of gun.
Learn more about our line of spray guns and related equipment — designed for home use, industry, professional painters, automotive refinishing and woodworking — that can be used in a wide range of applications.