A novel combination of analytical techniques for measuring optical properties of glaze and paint as input for computer modelling is used to investigate the influence of the green glaze layer present on top of the black underpainting in the background of Girl with a Pearl Earring. The absorption spectra of paint layers from paint reconstructions and samples of the original painting were determined using micro spectrophotometry. Additionally, Bidirectional Reflectance Distribution Function (BRDF) measurements were done on paint reconstructions to determine the reflection distribution from multiple illumination and observation angles. Already existing height and layer thickness information was compiled in a digital 3D model of the painting which, in combination with the optical properties, was used as a base for rendering using the Mitsuba render engine. The experimental results clearly show that the green glaze layer under specific angles darkens the appearance of the black paint onto which it is applied. The computer simulation shows promising results for digitally recreating the painting.