When Colour Measurements Disagree: A Protocol-Based Analysis for Cultural Heritage Diagnostics

Abstract: This preliminary feasibility study evaluates key operational choices affecting the repeatability of color measurements in cultural heritage applications. The investigation is conducted on a restricted set of representative pigments and is intended as an initial benchmark that will require further validation on a broader chromatic palette. Instrument calibration and scale adjustment followed established procedures and were not investigated. This work examines (i) the influence of the measurement area as a driver of experimental reproducibility, and (ii) the sensitivity of different illuminants in estimating variations of chromatic coordinates in terms of ΔE∗1976. Additional factors such as inclusion/exclusion of the UV-component and of the specular component are considered to contextualize uncertainty sources. The results suggest that the choice of measurement parameters (in particular, measurement area and illuminant) may lead to appreciable variations in the outcomes; however, more detailed and generalizable indications will require an expanded statistical basis and a larger number of measurements and cases.