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The desired appearance of powder coated ®lm depends upon the speci®c industrial application. While a glossy, mirror-like ®nish with a high distinctiveness of image (DOI) is required for automotive clear coat applications, much outdoor equipment and many household appliances require smoothly textured ®nishes that hide surface irregularities, ®ngerprints, and surface markings. This textured ®nish of powder coated ®lm, often termed orange peel appearance, can be controlled by adjusting the chemical formulation and the physical properties of the powder and by optimizing the electrostatic application process. These adjustments allow a wide-ranging control of gloss and orange peel texture. The chemical formulation of the powder is often determined by the functional needs of the coatings: providing protection against corrosion, heat, UV radiation, and physical impact. In many cases where the formulation cannot be changed, the electrostatic spraying process for the powder can be adjusted to achieve the desired gloss and texture.In electrostatic powder coating, back corona on the deposited powder layer often causes defects in the ®lm. However, if the electrical ®eld intensity inside the powder layer is below the breakdown level, the adverse effect of back corona can be avoided, thus improving the uniformity of the deposited powder layer. In the absence of back corona, increasing the high voltage applied to the corona gun improves both the smoothness and the glossiness of cured ®lms. Back corona can be reduced by increasing the surface conductivity of the powder. Increasing the relative humidity during spraying also decreases the roughness, since the augmented surface conductivity allows the powder layer charge to decay faster. The optimal relative humidity value for applying powder for uniform ®lm thickness was found to be 60%; increasing humidity beyond that point led to surface degradation, possibly due to excess moisture trapped in the powder layer. While the surface smoothness increased, the glossiness did not vary signi®cantly with the change in relative humidity. Another factor for ®lm surface properties is the``hiding power'' of the unevenness of the substrate surface. A rough substrate can be responsible for a rough ®lm surface when ®lm thickness is less than 25 mm. It was found that ®lms 40 to 50 mm thick can successfully cover scratches of about 20 mm depth on the substrate. Typical values of ®lm waviness varied from 1.5 to 3 mm, and ®lm roughness varied from 0.2 to 0.4mm for epoxy ®lm with 60 to 65 mm thickness.