How To Paint & Set Up Your Spray Gun
With Kevin Tetz
In September of 2013 Kevin Tetz from the Paintucation DVDs did a live stream and demonstration at Eastwood HQ in Pottstown, PA. If you missed it you can watch the whole thing on YouTube as Part 1 and Part 2, or just read our handy summary here covering all the topics he talked about including the live questions and answers.
A question that comes up a lot on the Eastwood forums and tech lines is “how big of a compressor do I need to paint a car?” Can you paint a car with a 2hp 15 gallon home compressor? Yes. Should you? No because you aren’t going to have enough air, or the clean dry air you need to atomize the paint for a proper glossy finish. A 2 stage, 60 gallon tank compressor with a 3.5hp motor should be considered a good starting point if you are planning on painting cars, preferably with a cast iron cylinder. And you need to go out of your way to be sure you have clean dry air. A larger tank and 2 stage pump means the compressor doesn’t have to run as often, and the air can cool down. Compressing air makes it hot, and the moisture gets trapped in it. Letting it sit in the tank lets it cool and the water sinks to the bottom.
Air Supply Plumbing
A lot of guys who have a good sized compressor, and an expensive high quality desiccant filtration and air drying system still complain about bad quality, moist air. One of the reasons for this is having the filter and water trap too close to the compressor. You need at least 20 feet, and preferably 50 feet so the air can cool and dry after being compressed. If you have a small shop it’s not feasible to just run 50 feet of pipe in a straight line from the compressor to the pain booth, but you can cheat.
The trick is to run 10 feet of pipe vertically, up and down, up and down, until you have 50 feet of pipe in about 5 feet of space. On this diagram A is the compressor (in the rafters), B is your desiccant filter (also up high), and C is a drain valve at the lowest point in the plumbing.
By cheating it vertically you create low spots where the water will naturally collect, and by putting the filter up high you are helping it do its job of separating it from the air. The best way to plumb the shop is with a “halo” style system. Run a loop of large diameter pipe around the perimeter of the shop, up to 2 inches, with 3/4 inch pipes dropping down to work areas where you need them. The pipe then becomes a secondary air storage tank, increasing your supply of air. Then if you slope the whole system downward, with a drain at the lowest part of the drop, and your regulator slightly above it, gravity will help you dry the air.
Fast Pipe Shop Plumbing
Modular air line systems, like the Fast Pipe system from Eastwood, make is very easy to plumb your entire shop with air. With its easy to cut tubing, easy to connect fittings, and aluminum construction is promises much cleaner air than the old black iron threaded tubing that was formerly the industry standard. Black iron and rust inside, and tiny flakes of iron or rust can find their way into the paint. These new systems use aluminum tubes, coated inside and out, to resist corrosion and deliver cleaner air. These systems were originally created for hospitals and the medical industry, so you know they provide pure air.
If you have an air aftercooler, do you still need 50 feet of air line? - No. Professional refrigeration systems typically are plumbed in right after the compressor, and before the tank. The air comes out, hot and wet, and gets super cooled before getting to the tank. A moisture separator is built into it and takes the water out as it cools. These systems are expensive though, and most home hobbyists aren’t going to have them, it’s more of a professional body shop set up. What has been done by some guys, with some degree of success, is to build your own out of an old kitchen refrigerator. Make several coils of copper tubing that fit in the freezer compartment. Make a hole in the side of the freezer for the tubing to go through, and back out. Hook the line from the compressor, to the freezer, then back to the compressor tank. Now not only do you have a way to cool the air, you can keep beer and lunch in the refrigerator part.
Because you need enough air volume, as well as pressure, it’s important to use a big enough hose. Never use an air hose smaller than 3/8 inch diameter, and 20-25 feet maximum between the hard line and the gun. With too long of a hose you are going to have a dramatic air pressure drop between the regulator at the wall and your gun. Use a good flexible air hose too, so you don’t get tangled, or end up having to move awkwardly while trying to spray.
It’s also important to use full sized 3/8 inch inside diameter air fittings on the gun and hose. Using 1/4 inch or 5/16 inch fittings or hoses can dramatically affect the spray coming out of your gun. With the same settings, same gun, same paint the fan pattern can be up to 4 inches smaller top to bottom, just with the wrong fitting.
Humidity and Time of Day
When you are painting, you often can’t plan what the weather is going to be like. Summers can be hot and humid and ruin a paint job, even with the best set up and technique. Use the time of day to your advantage. Typically mornings are the coolest, least humid, and most bug free time of day. Get all your set up done the night before and wake up with the sun to shoot first thing in the AM.
There is no need to think you have to spend a bundle to get a spray gun that will give you quality results. Learning the proper techniques and using them is more important than spending hundreds of dollars on a spray gun. Kevin Tetz’s 68 Mustang show car “Jaded” was not only painted with all Eastwood paints and primers, he shot it with the Eastwood Concours Pro and Evolution spray guns. On the floor at the SEMA car show, with other professionally built cars and even Riddler award winners, the paint on “Jaded” was just as good.
Technique Dos and Don’ts
A common mistake people make is in being lazy, or reaching too far ahead of themselves, and not keeping the spray gun perfectly perpendicular to the surface being painted.
When the spray nozzle is not held 90 degrees from the surface, the spray pattern causes one end to get too much paint, and one end to get too little.
Hold the gun just right and you get an even spray with perfect edges on your fan pattern.
A good way to practice this technique is to just tape a cheap 4” paint brush to the end of the gun. Practice keeping the brush just off the surface, and perfectly aligned.
Another mistake people make when they start painting is standing in one spot and just swinging their arm across the panel. This results in a curved arc of paint, not a straight line.
Kevin pulls an assistant out of the audience, and teaches him the correct way to work his way across the panel. Standing with your feet slightly apart, hold your arm straight, and move side to side at the hips, so the gun follows a straight line across the panel. Done correctly the gun will follow the tape on the box, or the black arrow, from one side to the other.
In order to maintain the correct straight line, you may have to bend your wrist a little at either end of your pass. But with enough practice it will become second nature, and you’ll do it instinctually. Another thing you can practice with the paint brush taped to the gun is your overlap. Proper overlap is typically about 50% from pass to pass. With the paint brush/spray gun practice tool you can move along the cardboard practice panel just like you were painting. Since the brush is about 1/2 the size of the fan pattern, you want to move the width of the brush with each pass.
On Gun Regulators
Small air pressure regulators are available and often used between the gun and the air hose. But before committing to using it like that, make sure it doesn’t cause you to hold your hand at an unnatural position.
It may seem okay now, but think about how it’s going to feel after you spray the 3 coats of base coat and 3 coats of clear all the way around the car. A better solution may be to use a regulator on the gun, and at the wall, then adjust the one on the wall until you get the pressure reading you want at the gun. Now you can take it off, and the gun is much easier to maneuver.
For the sake of practice it’s best to use something completely non-toxic, and paint something free and disposable. Today Kevin is painting a cardboard box using water based craft paint you can pick up anywhere. This makes cleanup super easy, and you don’t need to wear a respirator to spray it.
Open up the fluid control valve on the gun all the way and spray an example. If the spray pattern is not roughly football shaped, adjust the fan pattern control until it is. The dot at the top is wrong, the shape below it is correct.
A peanut shaped spray pattern usually means the air pressure is too high, and the air horns are pinching in the edges.
A banana shaped pattern typically means one of the air horns is clogged, the one the curve is bending towards.
A teardrop shaped pattern means your nozzle itself is partially clogged, or has some sort of dirt caught in it.
Cleaning a New Spray Gun
New spray guns are not ready to paint. Typically they are coated inside and out with an anti-corrosion chemical that needs to be cleaned off in order to get the best results. Since you don’t know exactly what they use, its best to just clean the gun like you would after using it. If you don’t clean it you can have problems ranging from dirt in the paint, to chemical incompatibility.
Leap Frogging a Car
You may not realize this, but it is important to start painting the car in the proper place, and work around it in the right order for best results. The order Kevin likes to use, which he calls “Leap frogging” or the push-pull method, is this: start at the edge of the roof and work toward the middle, from the other side start at the middle and work toward the edge, down the sailpanel, other sail panel, across the rear decklid and trunk, quarter panel, back to the other side quarter panel, door, other side door, fender, other side fender, hood, front of the car and done. This method means the edge of the paint is as wet as possible when you overlap it.
If you start in the middle of the roof and paint to the edge, you let that edge dry for several extra minutes before overlapping it and painting the other side of the roof. Then you have to apply the overlap extra wet to make up for the drying that has occurred. This is especially important since the roof of the car gets some of the worse that weather and nature can throw at it over the years, so you want it to be extra tough. Many pros do start in the middle and work toward the edge, but until you are a pro, Kevin suggests his method.
Finding the Wet Edge
How do you find the wet edge, when spraying the 2nd coat? Or spraying paint over a similar colored primer/sealer? Or when spraying clear? – Well, there is no trick, or easy way to do it. You just have to find the right angle, and look for the reflection of the shop lights, or sun if you are outside. You may have to move back and forth and up and down till you find it, but just keep at it until you find the light.
This is one of the reasons why you ought to be wearing eye protection when painting. With eye protection you can get your face right up close to the body as you spray and see the reflections. Even if you just wear a cheap pair of safety goggles and throw them away afterwards, they will keep the bounce back paint out of your eyes. Modern urethanes cure by the isocyanates reacting to moisture in the air. If it gets into your eyes, or other mucus membranes, it will start to harden and cure, and you don’t want that.
How is it that guys on reality TV shows can paint so fast? Is the film speeded up? – No, it’s not sped up. They are just good and have the techniques down. The first thing to consider is if you have enough air, and at the right pressure. If that checks out, then the most important aspect is having the gun in the sweet spot distance from the panel. Get the distance right and you can sweep back and forth almost unbelievably quick and get good coverage and perfect flow out. Also make sure you have a big enough tip on the gun, so you are getting good flow.
What size tip do you use for spraying primer? – It depends. Primer surfacer, which is viscous and high build is going to need a big tip – a 1.8 or 2.0. Polyester high build need a big fat tip like a 2.0 or larger. Other primers can be sprayed with anything bigger than a 1.6.
Why use a sealer? – The point of using a sealer is to have a continuous color coat to apply your top coat to. If the primer coat is already a solid color, and close to the color you are applying, you can eliminate the sealer coat. On the other hand, if you have a spotty primer coat, spraying 1 coat of sealer will mean eliminating several coats of top coat in order to get good coverage. Anytime you can eliminate a coat of paint and the solvents in it, you should.
For application over bare metal, after media blasting for instance, Kevin recommends epoxy sealer. Not only does it protect really well, and goes on easily, and can be coated over for up to a week afterwards without having to sand.
What has to be done to remove the coating left after soda blasting a car? – It is very important to use a cleaner after soda blasting to remove the thin layer of sodium left on the metal. The film will actually inhibit rust for a short period of time, but it has to be removed completely before any primer or paint goes on. Eastwood’s After Blast is a good way to clean and etch the metal between blasting and paint.
Of course do to the nature of this unscripted, live streaming demonstration, Kevin touched on a ton of topics. For more in depth explanation of paint and body matters the Paintucation DVDs are a great place to start, or the many other videos Eastwood and Kevin have done over the past few years now on YouTube.