
Three main aspects of the appearance of metallic coatings are color, gloss and texture (including graininess and sparkle). All three aspects can now be objectively measured using instruments according to ASTM and other international standards. However, there is no reason why these three aspects would be independent from each other. Indeed, it is known for more than a century that variations in color influence the perception of gloss. Here, we present the first systematic investigation on the influence of gloss variations on the occurrence of sparkle and graininess. We created a new, dedicated set of 462 solid and metallic paint samples, with systematic variations in color and gloss. We measured the multi-angle reflectance properties for all samples. Our results confirm that color strongly influences measured gloss values, especially for metallic coatings. We also show that there is a substantial influence from glossiness to the measured graininess and sparkle properties. For example, by applying a matte clearcoat instead of a more common high-gloss clearcoat on top of a metallic basecoat, the measured graininess reduces by 0.6±0.3 units and the sparkle grade at 15° by 3.3±1.7 units. This is in line with visual assessments on matte car paints: matte metallic paints hardly show sparkle. A physical explanation for these trends is presented.

We publish two carefully prepared and spectrally measured datasets of paint swatches. The main advantage of these datasets is that a diverse set of paint mixtures are manually prepared the way an artist may create them. The ratio of paints in each mixture is also published. The first set has 286 swatches made from 8 tubes of Old Holland oil paints in different combinations. The second set has 397 swatches made from 9 tubes of Schmincke watercolor paints. We provide exact details about the preparation of our swatches. We analyze the colorimetric and spectral properties of the two datasets in order to show the spread of the colorimetric gamut and the intrinsic, spectral dimensionality of the datasets. The dataset will be available on http://cam.mpi-inf.mpg.de/ and http://www.azadehasadi.com/.