687 Chapter 28 Spray Technique Copyright Goodheart-Willcox Co., Inc. for the air pressure to fully atomize the paint. Spraying too far from the surface causes some of the atom- ized paint to dry before it reaches the panel, leaving a rough, textured surface. Travel Speed Consistent spray gun travel speed is just as important as maintaining proper distance. Travel speed is the rate at which the tech moves the gun across the panel. If the travel speed is too slow, too much paint will build up. If the travel speed is too fast, not enough paint will be deposited on the surface. As a rule of thumb, the travel speed for a conventional gun should be about 1′ per second. An HVLP spray gun is held closer to the panel and moved faster than a conventional spray gun. For an HVLP spray gun, the travel speed should be about 1 1/2′ per second. Practice consistent travel speed by measuring a panel and timing the travel. Practice until spray gun travel speed control becomes second nature. Distance and travel speed are the two main factors that determine the amount of paint applied to a panel. Figure 28-21 shows spray gun movement on horizontal and vertical panels. Keep the spray gun fan perpendic- ular to the panel with a uniform orientation while moving it at a consistent speed and distance. It is important to remember that distance and speed are interrelated. The distances and speeds suggested previously are starting points. You must find the technique that works best for you. Some painters like to be close in and move fast others want to be farther away and move slowly. Different brands of spray guns may require modifications to your technique. Practice distance and speed together. Fasten a stick of the proper length to the spray gun, as shown in Figure 28-22, and mark off a panel into 1′ sections. Practice holding the spray gun the proper distance from the panel and moving at the proper speed. On a curved panel, practice moving the gun so that the stick lightly contacts the panel during the entire stroke. Less paint More paint • Wrist not flexible • Arcing gun • Uneven coating • Wrist flexible • Gun travels straight • Even coating Less paint Surface to Be Sprayed Surface to Be Sprayed Uniform paint thickness Incorrect - Arcing Correct DeVilbiss Figure 28-20. Arcing causes uneven paint application. Goodheart-Willcox Publisher Figure 28-21. A—Maintain consistent spray gun distance and travel speed on horizontal panels. B—Technician keeps the fan perpendicular to the vertical panel. A B