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What is air-assisted electrostatic spraying? Air-assisted electrostatic sprayers produce electrically charged spray droplets which are carried to the target in an air stream. Electrical charges on the surface of the spray particles cause them to be attracted to the target where they are directed. Coulomb's Law says that opposites attract, or more specifically, unlike electrical charges attract to each other. Because of Coulombic forces when charged spray particles are near any object they will be attracted to that object. They will follow electric field lines and wrap around and coat all sides. ESS takes advantage of this physical principle to allow spray applicators to do a better job and to help provide less environmental impact. In addition ESS uses air-assistance to help with spray delivery. Air is necessary in electrostatic spraying to cause the charged spray to push deep into complex targets, such as tall plants. Electrostatics, with air-assist, plus the right droplet size is a good combination for the best spray job. The force of electrostatic attraction is strong if the droplets are small and the droplet charge is sufficiently high. ESS sprayers produce highly charged spray droplets using a unique "embedded" induction electrode design. The result is the droplets have a force of attraction of 75 times that of gravity. This means droplets will reverse direction and move upwards, against gravity, to coat hidden surfaces. In agricultural spraying underleaf coverage is important since insects and diseases are located almost exclusively on leaf bottom-sides and other hidden areas deep in the crop. In the photograph above electrostatically charged spray is shown coating a plant leaf. Spray droplets move along electric field lines (Coulombic Forces again) and reverse direction to coat the underside of the target. Droplet size is important. If droplets are too heavy (over 60 microns) then no matter how highly they are charged they won't reverse their direction against gravity. MaxCharge droplets are 30 to 40 microns in diameter and charging levels are normally 6 mC/liter. This size droplet with this high charge results in attraction forces over 75 times that of gravity. This photograph shows how insect populations live mostly on the leaf underside. These are whitefly infestations on cauliflower in Yuma, Arizona. In this case the grower had treated the field several times with a conventional sprayer with full chemical rates. As you can see the insects on the underside were not controlled. This is the same leaf after spraying with an ESS field sprayer. This photograph was taken 4 hours after treatment with only 50% of chemical rate.

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