Techniques de décoration sans apport de matière par mesure optique sans contact de l'état de surface : première approche aux bijoux mérovingiens Decoration techniques without material addition by non-contact optical surface characterisation: fi rst approach to Merovingian jewellery

An analytical protocol for non-contact surface characterisation based on chromatic-coded confocal imaging was applied for the fi rst time to the study of tool marks on jewellery items in order to identify the employed technique and type of tool as well as the goldsmith's gesture. In this study we considered decoration techniques consisting of addition of patterns by removing material or by mechanical deformation of the plaque particularly engrav- ing, chiselling and stamping. Th is development was based on chased and engraved motifs produced in a goldsmith's workshop. Th e protocol was applied to the study of a gold fi nger ring and a pair of silver fi re gilded fi bulae found in two tombs of the Merovingean necropolis of Louviers (Eure). We could show that the fi nger ring consists of two parts made by two diff erent workshops and that the pair of fi bulae is dissymmetric, each element of the pair being of independent manufacture.