Spray Gun Technique

Safety - Protect Yourself!

The absolutely first step in painting is to protect yourself. Paint is toxic and can be breathed in and absorbed through the skin. Will it kill you if you don't wear any protective gear - probably not BUT it will hurt you and create long term problems. The more exposure that you get, the more problems that will turn up later. Play it safe and wear proper protective gear - it is surprisingly inexpensive. Do it right!

A respirator protects you from air borne particles. You should be wearing one that has filters that protect specifically against paints and solvents. The filters are replaceable and some filters are just for dust. The little medical style dust mask will NOT do. A simple test after painting is to blow your nose and check your tissue, if there is paint residue then your respirator is NOT working and you are risking serious health problems.

A full face covering mask respirator is ideal except that you need fresh air fed to it from a non oil air compressor source. This mask covers your face and eyes.

This is a dust mask and is NOT acceptable to use when painting! Don't even think of using this dust mask!

This is a good paint respirator for the DIY painter

Inexpensive paint suit that is good for the DIY painter

Throw away gloves are a must. The plastic gloves on the left tend to tear easy and are difficult to use. The latex ones on the right are preferred.

Setting Up the Spray Gun

Once your ride is ready to be painted, you have a spray booth setup, you have your protective gear on and the paint mixed to the manufacturer's specs then you are ready to setup your spray gun. There are four settings that affect your spray gun:

  1. Air pressure
  2. Material adjustment
  3. Pattern Control
  4. Air cap rotation

This video discusses the four settings and how to adjust them. It gives some good tips:

Adjustments

There's three adjustments that you can adjust on the touch-up gun: pressure, material and pattern:

Pressure

The first control is the air pressure which I set at the gun. The paint instructions will state what the paint pressure should be at the gun handle. HVLP gun instructions will state something like it requires 45 psi at the gun to shoot 10 psi from the tip. While the 45 psi is the same pressure as the older high pressure guns, the actual pressure at the tip is only 10 psi. The air pressure is critical for correct atomization of the paint. You want fine even droplets at the edge of the spray pattern. You should have a regulator at the gun to control the air pressure.

Material Knob

The second control to set is the material knob. The material knob sets how much paint is sprayed. The rule of thumb is to screw the knob all the way in and then out by 2 1/2 turns. his is the initial starting point that manufacturers recommend. The next time, I spray, I'm going to try adjusting it this way and the method shown in the above video to see which is better. I check it by test spraying a piece of masking paper so that the paint didn't run after spraying and holding for 2 seconds. You shoot about 8"-9" from the surface. Naturally, all three adjustments interact with each other - so you may have to run through the steps several times to get the right combination!

Fan Pattern

The fan control which sets the shape of the spray pattern. It should look like a "cigar" and be even spray throughout. I set it for about 6" to 8" wide depending if I was painting tight small areas like the dash or larger areas like a body panel.

Fan out of spray pattern

Interestingly, the gun tip is at 90 degrees from what the spray will be. The gun tip can be rotated to any position and tightened.

Poor Pattern

This pattern has very poor atomization as can be seen from the large droplets. It may not have enough air pressure or there is too much material being shot. Usually if there is too much material, then the paint will run with the 2 second test. It also looks like the gun was tilted towards the top when held as the top is thicker and has more paint.

The most important step is to test your settings by spraying on a piece of cardboard or flat surface. You should be able to spray for 2 seconds without running with a fine even atomization. This should be done every time you use the gun and in between coats. There are a lot of factors that come into account when you are setting up your spray gun: paint viscosity, air temperature, air humidity, paint tip, type of paint, etc... Only adjusting the gun and testing it will let you shoot a perfect coat.

Always use a paint strainer when filling your spray gun paint pot!

This is a very good video from SATA (a leading paint equipment supplier) that discusses many important techniques in laying down paint.

This is a very good video where an experienced painter talks about the art of painting while he paints a car. There are a lot of extremely good tips as he lays down a custom candy apple red coat.

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Copyright December 2011 Eugene Blanchard