Pompano Beach, Fla. - ASTM D 523 describes three measurement angles to measure gloss across all surfaces. Gloss is measured in gloss units (GU) and is traceable to reference standards held at BAM (Germany), NRC (Canada) or NPL (UK).
Universal Measurement Angle: 60°: All gloss levels can be measured using the standard measurement angle of 60°. This is used as the reference angle with the complimentary angles of 75° and 20° often used for low and high gloss levels respectively.
Low Gloss: 75°: For improved resolution of low gloss a grazing angle of 75° is used to measure the gloss of paper. This angle also has a larger measurement spot which will average out differences in the gloss of textured or slightly uneven surfaces.
High Gloss: 20°: The acute measurement angle of 20° gives improved resolution for high gloss surfaces. Surfaces that measure 70GU and above at the standard angle of 60° are often measured with this geometry. The 20° angle is more sensitive to haze effects that affect the appearance of a surface.
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