*2.3. Reflectance Spectrophotometry (RS)*

Reflectance spectra were taken using the X-rite eXact spectrophotometer in the range of 400–700 nm with a 10 nm resolution and a 4 mm diameter spot size. The purpose of these measurements was to identify colors with the same signature spectra across multiple plates and not for pigment identification. It was thus deemed acceptable to perform the measurement through a clear mylar (PET) film (3.8 microns) to avoid direct contact with the surface (preliminary test indicated a 90% reduction in the reflectance).
