Paint Sprayers and Other Tools
Spray painting is the fastest way to cover large areas -- spraying can be as much as four times faster than brushing and twice as fast as rolling. Sprayers put paint easily on hard-to-reach surfaces, such as soffits and lattices, and deeply textured materials such as stucco -- areas that a brush or roller can leave untouched.
With spray equipment, you can paint objects with irregular or complex shapes, and because sprayed paint does not show brush marks or roller stipple, it results in a uniform appearance.
One inherent drawback however, is that the smooth surface resulting from spraying can be difficult to touch up, and some painters insist that sprayed applications be back-rolled so that the job can be touched up, if necessary. And no matter how powerful, no sprayer can overcome the effects of winds or even gentle breezes. Dead calm is the best weather for spraying outdoors.
There are several major types of sprayers -- conventional, airless, and high volume low pressure (HVLP).Conventional spraying
Conventional spraying uses compressed air supplied by a hose to atomize and propel paint, supplied to the gun from a cup or through another hose. The design of the spray gun nozzle controls the spray pattern.
Internal mix guns require less air pressure and less air volume. That makes less overspray and a thicker coat of paint.
External mix guns are popular because they control the spray pattern better and there is less wear on the gun.
Cup sprayers are ideal for small jobs. The cup is attached to the spray gun and usually holds 1 to 2 quarts of paint. Paint is fed either with a gravity or siphon feed system.
Conventional spray equipment can apply many types of paint, from thin lacquer to heavier latex paint. However, conventional spraying requires thinning of heavier paints, which can ultimately result in a failed coating. For that reason, paint manufacturers often discourage thinning for spraying by providing little or no information on how much to thin the paint. Conventional spraying also produces a great quantity of overspray, which increases the amount of paint needed to cover the surface.Airless spraying
Airless spraying is popular because:
- Its high pressure (1,500 psi or more) alleviates the need for thinning most paints.
- Overspray is minimized.
- It applies paint more quickly than any other method.
An airless spray gun looks like a conventional spray gun except there is only one hose connected to it -- the paint supply hose. There is no air-supply hose because the paint is pushed through the paint hose by a pump.
Airless spraying puts paint on at least twice as fast as conventional spraying and produces less overspray. Airless units are also more portable, less cumbersome, and easier to clean.
When spraying, maintain a distance of about 12 to 14 inches between the spray gun and the surface. Holding the gun too close results in sags and runs; too far away applies a coat that's too thin.
An airless system has only two settings: on and off. You can't vary the paint flow with the gun control. You have to keep the gun moving at a speed that is comfortable and provides proper coverage.
OSHA requires the mandatory use of a tip guard to help prevent a major injury -- the high pressures of this system can actually inject paint into flesh, which can cause serious harm and even be lethal.High volume, low pressure spraying
High volume low pressure (HVLP) spraying describes a system that uses a large quantity of air at only 10 psi to push paint through the spray head and atomize it. The result is a very fine mist that produces a minimal amount of overspray.
Because more paint reaches the surface, HVLP is ideal for interior applications, confined areas (such as closets), trim, doors, frames, cabinets, shutters, and other fine finish work. HVLP is not typically used for large areas because paint goes on at a much slower rate than with airless spraying.
Many HVLP sprayers cannot handle heavy paints with high solids unless they are thinned, which can compromise the quality of the coating. A larger compressor can often provide a suitable compromise.
Most manufacturers offer a variety of nozzles for special applications and the option of using compressed air with an HVLP gun or an accessory kit that converts a pressure tank for use with HVLP systems.
HVLP spraying techniques are similar to those for conventional spraying but with the gun held 6 to 8 inches from the surface. You should overlap sprayed areas by 50 percent.
HVLP is as fast as or faster than conventional spraying but slower than airless spraying. You can adjust the speed at which the unit applies paint by changing the nozzle size. The larger the nozzle, the faster the application.General application tips
No matter what kind of sprayer you use, here are some general practices that will ensure a consistent and safe application:
- Test the sprayer and your technique on a large piece of cardboard. Adjust the spray head and pressure to get a uniform pattern with a minimum amount of pressure.
- To achieve a smooth, even coat, keep the gun moving across the surface in a succession of overlapping strips. Move the sprayer in a smooth motion and at a consistent pace. Release the trigger at the end of each stroke, and then pull it again as you begin to reverse direction.
- Spray straight at the surface; avoid swinging your arm or hand in an arc.
- Once you have begun to work, do not leave the sprayer idle for more than 20 minutes or the paint will begin to harden.
- When you have finished painting for the day or are taking a break of some length, clean the paint from the unit, carefully following the manufacturer's instructions.
- To avoid mishaps or injury, always wear protective clothing and gloves, as well as goggles. Never point the sprayer head at your body or anyone else's. The powerful jet of paint from a sprayer can force paint through your skin. If that happens, get immediate medical attention.
- Before you clean a power sprayer, turn off and unplug the unit. Then pull the trigger to release the remaining pressure in the hose.
- Make sure to set the safety lock on the spray gun when you are not spraying.