Measuring the Glossiness of Effect Coatings

ABSTRACT Gloss is an important feature of the visual appearance of materials. Industrial gloss meters are based on the assumption that gloss perception is determined by the amount of specularly reflected light. Past studies identified many factors that determine the correlation between gloss perception and instrumental gloss characterization for a range of materials. In this article, we extend this research by investigating factors that influence instrumental gloss characterization, focusing on materials that so far were hardly investigated in this respect. To investigate the effect of coatings such as metallic paints, we use a dedicated set of paint samples. Since various effect coatings differently influence the angular distribution of reflected light, instrumental gloss characterization is more complicated than for conventional solid coatings. We show that when using conventional gloss meters on effect coatings, the measurements systematically deviate from gloss values measured on corresponding non‐effect coatings. At a 60° detection angle, gloss measurements on metallic coatings are 3.8–6.2 Gloss Units higher than for conventional coatings, but only if the glossiness at 60° is higher than 35 Gloss Units. The largest deviations occur for bright metallic colors. We present a model to correct for bright near‐specular reflectance. By applying this correction, the average gloss deviation for metallic colors reduces from 5.7 to 2.8 Gloss Units. Measurements of gloss values for metallic coatings are strongly improved by using the proposed correction.