Download this Compressor Buyer’s Guide (PDF) (New! 2014 Edition)
by Pete Johnson
Looking at a matrix of compressors and their attributes on a printed page can be challenging. When I bought my first compressor, I had read a zillion articles (this was pre-Internet) but ended up calling a knowledgeable retailer and saying, “Help!” My needs were easy to diagnose and I got a compressor. A few years later, I bought another.
With special gear, you tend to trade up as you know more, or because your business grows, or both. You musicians reading this know what I’m talking about.
I’m not here to push one product or another, but rather, present experienced viewpoints that touch on compressors in general as well as some specific models. You may like others; write or email us and tell us why.
Also, some disclosure here. I own a Silentaire TC-30. It’s a portable (well, luggable) oil-and-piston compressor that fills a small reservoir tank and has an auto shut-off valve. I had a Silentaire 20 that was a little smaller. I used the daylights out of it, never had a lick of problems, and gave it to my brother, who happily uses it to paint woodcraft items like duck decoys. He’s pushing thinned oil paints with it, I might add. But my TC-30 is perfect to take with me to do detail work on
everything from leather to metal or the occasional small mural. In my book, the money you pay for a quiet compressor with a reservoir, filter, and automatic shutoff is worth the investment if you’re doing any kind of professional paint work, or want to. But if your needs are smaller, your compressor can be, too.
New gear has come out in the 10-odd years since I bought a compressor. The usual beginning is, “I want a compressor. Where do I start?” How do I choose?
There are some first-order questions and answers.
First question in choosing a compressor: What price do you want to pay, and how many cubic feet per minute (CFM) of air are you looking to move?
CFM is important if you intend to also power a spray gun from a compressor. If that’s the case, then a small studio compressor just won’t do. Especially if you’re using an HVLP gun, which might have a low nozzle pressure of 10 pounds-per-square-inch (psi), but eats up three times the volume of air that a conventional spray gun uses.
General note also here from your writer: A lot of us have a homeimprovement-store compressor in the garage to fill the Harley’s tires and blow the dust off of stuff. It probably has a 30- or 80-gallon tank.
The thing raises pure noise hell when it runs, and gets hot. These kinds of compressors are generally unsuitable for powering your high-end paint projects, because of well, the ruckus, but more importantly, the heat from the simple diaphragm motor. Moisture condenses in the tank and the lines. Then, if you use an HVLP gun, these compressors usually run constantly, compounding your problems. So think about not using one as your home spraybooth air source, even with moisture traps and line filters. I know we’ll get a million emails from people who do, but just use your head, and it might be better to use your utility compressor for blowing primer on drywall and so on.
Second question for compressor shoppers: What kind of paint do you spray, and on what surface?
If you’re doing two kinds of work, say T-shirts and automotive, get a compressor for the heaviest load, which is fabric paint. As a rough estimate, you’ll probably need a compressor that handles a steady
30- to 35-psi for automotive work, and 50- to 60-psi for textile paints if you do T-shirts.
And the third question: What’s the difference in compressors?
Compressors are basically just refrigerant motors that have been tuned and improved. But each is a little different. Let’s talk about the major kinds.
Small diaphragm (hobbyist) models
Diaphragm compressors are inexpensive, but don’t let that fool you. The manufacturer might say it produces air at, say, 45 psi, but when you press the trigger, the pressure drops significantly. So if you’re just doing small hobby jobs, it might be OK. Some of them pulse and deliver surges of air that make paint flow unpredictably.
One problem is that some manufacturers and retailers sell these small diaphragm compressors for ‘beginners.’ Unfortunately, these models might not be up-to-speed for a beginner who, say, is starting to do T-shirts or auto work. Any time your airbrushing requires a constant flow of air, with the trigger down, you need a larger compressor with a reservoir. And that description fits a whole lot of artists buying a new compressor.
Here’s a familiar scenario: A new artist buys one of these small, diaphragm compressors because it says ‘beginner.” Then the artist starts having problems. Paint won’t flow. There’s moisture coming out of the airbrush and ruining the job. Then the newbie, because he or she doesn’t know any better, blames the airbrush, the paint, or both.
Sometimes people get frustrated and give up hen in reality, a better compressor for a few more dollars would provide steady air pressure, filter out a lot of the moisture (or never produce it to begin with), and in the bargain run a whole lot quieter.
In the small compressor category, the Iwata Smart Jet develops around 35-psi. It’s simple and could be a good choice for a hobbyist, nail artist, or other light work. It even has a moisture trap and is headand-shoulders ahead of some of the cheaper models. But automotive work and T-shirts need more air pressure from a larger compressor.
Comparison and Price Charts
(click on the thumbnails to enlarge the charts)
Compressors from Iwata-Medea
Compressors from SilentAire
Compressors from KopyKake and Aztek
“Silent,” automatic shut-off compressors
Silent compressors come with an auto shut-off switch, so when the compressor fills to a certain capacity, the motor shuts off. This is good for motor life, and keeps the compressor from getting hot. Heat can create problems with moisture cycling through and into the air line.
The two basic types are those using oil for piston pressure, and oilless. There are a number of different ways that a compressor regulates pressure and lets the air flow. Some models come with a diaphragm regulator, versus a spring-loaded bleeder. Also, there are single-piston models, and twin-piston. The twin-pistons build up pressure faster, for
Basic physics says that the temperature of a gas has a direct relationship with pressure when volume is constant. If temperature increases, then pressure increases, and vice versa, when volume is constant. But as we’ve mentioned, it’s usually direct motor heat, generated by the friction of moving parts, that has to be dealt with. Interestingly, the Power Jet Pro is larger but runs a little warmer filling the larger air tank which can attract moisture that must be filtered out, so
the advantage in capacity can be cancelled out by the moisture issue.
Wet, Soggy Stuff In The Middle of the Night
On that note, let’s really get to moisture traps. They’re critical if you’re serious about airbrushing. Use your imagination; it’s 2:00 am and you’re finishing a tricky, beautiful job, and your airbrush blasts a spurt of water along with your paint and ruins everything. It’s a mural of ‘Mom’ (isn’t all popular art a variation on tattoos?), on a big-twin motorcycle that belongs to the Prez of the local chapter of the Death Dudes motorcycle club. He’s picking it up when your shop opens at 8. A good moisture trap might have come in handy. Iwata, anyway has a coiled hose underneath some of its Studio compressor bodies (the Smart Jet Pro and Power Jet models come to mind), which then feeds into the moisture trap. This is great, because it allows the air to cool, then the remaining moisture is removed more efficiently in the moisture trap. This means very little water getting into your final air line and onto your work.
Other Common Malfunctions and Troubleshooting
This isn’t that last word, because compressors have many moving parts and a number of stress points. But here are some common sense ideas from the Airbrush Action brain trust. power. Check that the compressor is plugged in. (Not kidding here. You’d be surprised, or you wouldn’t.)
Compressor motors, and compressor electrical cords, draw lots of amps. They could overheat and cause mayhem. 110-volt compressors can quickly max out a home or light-duty electrical system. Try not to use extension cords; plug the compressor in close to a power source that’s built to code. If you must use an extension, make it as short as possible, and use a heavy-duty cord.
Of course, if your compressor is some big suckah putting out shop air, you already had a qualified electrician run 220-volts to the thing. But most of you reading this guide are shopping for a smaller machine.
Air Leaks. Make sure that if the compressor has a moisture trap, the airtight drain is closed and locked against air leaks. All air connections should be tight. Check the intake filter. Then try to run the compressor and put your finger over the intake (minus the filter). There should be a steady suction. If there isn’t, it’s possible that there is a leak in the tank connections, or a faulty valve is routing air back around the jacket of the tank or elsewhere.
Dirt. This seems simple, but keep the outside of your compressor clean. Dirt, oil, and other foreign substances can seem benign, but can keep heat inside your compressor instead of it transferring though the outer metal to the air, cooling the components.
Oil. If you’re using your oil compressor off and on, 9-5, every day, professionally, change the oil every six months. For heavy use—such as shirts in a mall, running day in, day out, change the oil every three months. But for average studio or home use, one change per year is usually sufficient.
If you find any discoloration, or especially a burnt smell in the oil, it is breaking down and needs to be changed to ensure the full future life of your compressor. And use the oil that the manufacturer recommends, not the stuff you pour into your powerboat or ATV engine.
Dealing with thornier compressor problems might tax your ability, tool set, or both. When in doubt, contact a warranty repair facility.
Burnt or corroded valve plate. If a silent compressor keeps running, or has other flow problems that aren’t obvious, it’s possible that you have a burnt or corroded valve plate, and air could be leaking out into the motor housing instead of remaining sealed. Take the intake off and put your finger on the intake tube while the compressor is running. Make sure there’s suction coming in. If not, it’s repair time.
Ball Chuck or one-way valve. This valve can get dirty or overheated. In the latter case, the valve components can actually swell and stick, keeping the valve in the open position. This can be a source of your airflow or motor malfunctions.
SeIzed motor. The piston can stick in its cylinder if an oil compressor runs low, or runs out of oil. This can be tricky to fix, but sometimes not impossible. When the components cool, the piston may respond to progressive traction or pressure, depending on where in the cylinder the piston is stuck.
Heavier electrical problems. On a bigger motor, a starter relay or capacitor can fail, and the motor won’t start or run. Some compressors also have circuit breakers in the form of a thermal switch, which heats while under excess load, then resets. If the element or metal inside corrodes or breaks, the compressor doesn’t start. A lot of motorcycles have a main breaker up under the seat or elsewhere that functions the same way, if that helps you visualize this. The main
breaker is usually the first place you start with electrical problems, besides making sure there’s electricity.
Naturally, there are entire programs in compressor maintenance taught at community colleges across our land, and so it’s hard to squeeze the topic into a buyer’s guide introduction. But we’ve presented a new buyer some ideas, and experienced artists are encouraged to look at some of the new compressor models. You might be surprised at the
range of innovations.
Download this Compressor Buyer’s Guide (PDF)