Surface Smoothness and its Influence on Paint Appearance. How to Measure and Control it?

Abstract

This chapter discusses the different parameters of gloss and their effects on the paint appearance. The measurement and control of color and gloss parameters is critical because of esthetic reasons and provides an indirect measure to control process parameters. The impression gloss consists of several appearance phenomena—specular gloss, haze, distinctness of image (DOI), and surface smoothness. It is a combination of focusing on the reflected image of a light source and focusing on the surface, evaluating the contrast between highlighted and non-highlighted areas. The evaluation of surface smoothness has major influence on the total appearance and is currently only evaluated visually. In a case study, the influence of substrate roughness, baking position, and clear coat layer on the surface appearance are evaluated by using a new objective instrumental method for measuring orange peel. To evaluate the appearance phenomena, orange peel, the instrument simulates the human eye by focusing on the surface and measuring the contrast between the dark and light areas. The measurement results are divided into long-term and short-term waviness, which have a direct correlation to different process parameters such as substrate roughness, baking position and with or without clear coat.