1. Chemical imaging of tracings to reveal inscriptions and symbols

Tracings, being inscriptions, drawings, signs or symbols, may no longer be accessible today, either deliberately hidden so as to lose the information they carry (redaction), involuntarily because the support has been reused for its mechanical properties to the detriment of what it carried (palimpsest, fragments in book bindings or as lining in musical instruments), or degraded by the object's use or environmental impact.

Even when they are invisible to the naked eye, imaging techniques can be used to find these tracings. The "Tracings" group is involved in a number of research projects allowing the development of methodology and the implementation of imaging techniques to reveal these lost tracings, such as the use of X-ray fluorescence imaging to reread sheet music stuck to the spine of a book, or to support the rereading of letters from the correspondence between Queen Marie-Antoinette and the Count von Fersen (REX II project).

Among the research projects aiming at using chemical imaging to visualize inscriptions that have been partially erased by use and time, the project on the collection of musical instruments collected by Victor Schoelcher from the musée de la Musique (Paris) shows the importance of recovering information born by these inscriptions in order to place the collection in a precise historical and geographical context.

The pictorial material used in tracings can disappear (loss of cohesion, abrasion) or visually change (physical or chemical transformation), sometimes altering the reading of the drawings and symbols they represent. To rediscover their meaning, the "Tracings" department uses a range of analytical techniques to characterize the original materials used and, in particular, rediscover their distribution and appearance, as in the case of the revelation of lost royal emblems on musical instruments made by Andrea Amati.

2. Identification of the metal-gall inks composition for a better understanding of the historical context of tracings production

Analysis of the materiality of the tracings enables us to identify the chemical composition of the original materials used, which in turn helps us to understand the historical context in which they were produced and to study their preservation, in collaboration with historians, curators and conservators.

In the study of metal-gall inks in particular, the CRCC team has a long experience of these materials, their history, manufacture and evolution. Through physico-chemical analysis, the "Tracings" group gathers information to answer questions raised by their use. Comparing the chemical composition of iron-gall inks from different objects or eras, and in particular the concentrations of metallic elements such as iron, copper and zinc, enables us to group together inscriptions that may be linked by various parameters.

Manuscripts from the Mont Saint-Michel (10^th-11^th centuries) were a particularly valuable source of material and historical information (EMMA project). In particular, analysis of the inks used in the writings of several of these manuscripts has enabled us to observe a major change in composition between two chronological periods, raising questions about the manufacture of inks and their supply to writing centers.

In a project carried out on wooden tools from Stradivari's workshop in Cremona, from the musée de la Musique collection (Paris), the study of the inks chemical composition raised questions about how to distinguish the authors of different inscriptions.

The study of Merovingian papyri and parchments, and in particular the analysis of the inks used on these different media and according to the type of certificate produced (royal, private, etc.), will also provide an opportunity to place the study of these materials in a particular historical and geographical context (PapMedAn project).