Modelling the orange-peel texture for chromatic and achromatic samples

Abstract

The aim of this study was to quantify orange-peel texture with an instrumentally based single-number index highly correlated with equivalent visual assessments. We prepared 3 achromatic (black, grey, and white) and 4 chromatic (red, green, blue, and yellow) scales, each with 8 different levels of orange-peel texture. Each scale had a sample with a minimum degree of orange peel, which was considered to be the standard sample. The visual differences between the standard sample and the remaining ones with progressively increasing degrees of orange peel in each scale were assessed by a panel of 28 observers using a prepared one dimensional lightness scale based on CIELAB. The usual parameters for surface texture provided by the BYK instrument were measured for each of the 56 paint samples and used to develop different models under the assumption of the additivity principle. The coefficients of these models and their performance with respect to visually assessed equivalent differences in orange peel were determined. Ridge regression was used to address multicollinearity between parameters. The validity of the models derived as well as other indices were further tested using the ACT (Advanced Coating Technologies) standard panels. ANOVA analyses indicate that chromatic samples have no adverse significant effects on the orange peel. Predictions of visual orange peel texture results by one of our models are considerably good [R2 = 0.98; STRESS (Standardized Residual Sum of Squares) = 6.3] and therefore, this index is recommended as an index of orange peel.