The interdisciplinary AORUM project aims to study gold as a painting material in artistic practices in Western Europe between the 16th and 17th centuries, a period when it is usually thought gold is no more used in artistic pratices of painting. Its ambition is to gather an original corpus of artworks and to analyse it from a threefold perspective (historical, technical and optical). Indeed, contrary to what the prescriptions of 15th and 16th century painting theoreticians (e.g. Alberti and Vasari) would suggest, gold continued to be used in the 16th and later. This is evidenced by some paintings of such famous artists as Raphael, Dosso Dossi, Frans Floris, Rubens, Rembrandt or Vermeer. There are many other examples, yet gold is the one material that is largely absent from the work on early modern European painting. The objectives of the AORUM project are precisely to bring this largely ignored corpus out of the shadows; to analyse it according to the usual questions of art history (iconography, social history, history of taste, etc) ; to study, in an interdisciplinary approach (Technical art history – physical-chemistry of Heritage artifacts), the history of the gilding techniques; to analyse the optical properties of the different gilding techniques, the optical effects generated with regard to historical and current lighting, again in an interdisciplinary approach (art history - physics); finally, to manage all the data in such a way as to contribute to the EquipEx+ ESPADON, and to valorize these data and the results for art historians, curators, restorers, and the general public.