Quality Finish? Speed and Distance Are Critical

By Bernie Bottens | Posted: 07/11/2013 10:33AM

 

Bernie Bottens how to finish wood Speed and distance are your friends (SADAYF) when it comes to getting the best finish on a project. The distance that the spray gun tip is from the object being sprayed is important as is the speed with which you move the gun over the surface being sprayed. SADAYF if they are used correctly. They are your enemy if they are not.

Speed controls the amount of coating that is applied per pass to any given square inch of surface. The faster that the spray tip travels over the object, the less that you apply. That could be really important if you are shading something and the shader is really strong or the need for intensity change is minimal.It could also be critical if you are applying a coating of very low viscosity. Going too slowly will create runs.

Not moving across the surface at a consistent speed means that the coating will not be applied evenly.

The distance that the tip is above the surface being sprayed also affects the amount of coating applied per square inch. The farther you are away from the surface, the bigger the fan pattern is and the more disbursed the coating will land. At the same time, not being able to maintain a consistent distance even when gun speed is perfect will mean that the coating will be applied unevenly. There will be heavy areas and light areas.

Discipline yourself to find and maintain the “sweet spots” of distance and a constant speed. These sweet spots are at the core of good gun technique.

Having said that, here’s another way to discipline yourself. I see a lot of people who use their forearm incorrectly when spraying. Most of the time I see them use their wrist (forearm rotation) at the beginning and end of a pass to make up for not using their wrist, arm, and body to keep the gun moving precisely. Instead of using their arm and their body, they use their wrist. The end result of this is less coating on the leading and trailing edge of an object and more in the middle.

Let’s look at this point more closely. Once again, SADRYF. Using your wrist will increase your speed as well as increase your distance. Always, ALWAYS, ALWAYS keep the fan pointed perfectly perpendicular to the surface you are spraying. Think about that and you will realize that that involves two planes of operation. But, never, ever wave the spray fan by rotating your forearm…use your whole arm as well as your body to keep the fan perpendicular to the surface. Use your wrist only to keep the fan pattern perpendicular to the line of travel all the way through the pass. That is essential to consistent millage on the surface.

Now, let’s look at that from another direction. Let’s say that you don’t use your wrist and arm to keep the fan pattern perpendicular to the line of travel all the way through the pass. What will be the result? The first answer that comes to mind would be that you will be spraying in an arc instead of a straight line. The second possibility would be that your pattern will be narrower at the start and the finish and wider in the middle because of spray head rotation.

Again, this doesn’t mean that your wrist doesn’t move freely. It just means that it moves in one plane as a result of what your whole arm and your body are doingto keep the fan perpendicular to the surface and to move the gun along at a constant speed.

It’s hard to do this well. It takes daily, thoughtful practice. It’s mentally and physically tiring to do this well and you will need to work at developing your “chops” in the same way that a trumpet player or a down lineman, or a tennis player develops their winning ways. There is more than a bit of muscle strength involved as well. That comes from constant repetition.

Your body, as a robotic machine, must be programmed to maintain a certain gun distance, a certain speed, and a specific angle of application all the way across the pass. It must have the muscle memory to do that same thing pass after pass…even when it gets fatigued. Your whole upper body gets a workout. But the key to practicing good habits is that, like the robotic machine with its computer, your brain must be actively involved to make the arm move correctly or nothing outstanding will come of it.


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About the Author

Bernie Bottens

Bernie Bottens (WoodworkingNetwork.com/blogs)writes and teaches on the subject of wood and wood finishing in industrial woodworking. He and his wife, Carol, live in Vancouver, WA. Bernie has been teaching wood finishing to shop owners, shop foremen, spray technicians and finishers all over Oregon, southwest Washington, and northern California for the past 9 years. Prior to that, he owned his own cabinet shop. His shop credentials include apprenticing and becoming a journeyman exhibit builder. Before that he taught in the public schools for 20 years. Bernie is the owner of Kapellmeister Enterprises, Inc. and Kap Coatings Consulting. Reach him at kapenterprises@msn.com.

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Alexandra N Le    
Auckland  |  December, 16, 2013 at 12:17 AM

Sir...thank you for sharing your thoughts that might help me as a newbie to improve my work quality and quantity. Also i would like your comment on < a href="http://www.wood-x.co.nz/additional- information/finish-your-decking-with-wood-x-cedar-stain/">how to stain cedar my new wooden benches.

 

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