Gilt leathers are luxurious decorations used all over Europe to embellish the interiors of the richest residences, dating predominantly from the 16th to the end of the 18th century. Despite the name, they are not defined by the presence of gold. Instead they were made by applying to the leather a silver foil which had the appearance of gold after being covered with a yellow varnish. As gilt leathers are often not signed, dating and classification are usually assumed based on stylistic studies.

A collaboration gathering scientists, a conservator, an art historian and curators started in 2011 to develop research on these decors. The aim was to characterize the different components within gilt leather to learn about the manufacturing technique, in particular the recipe specific to each workshop, and to better understand the degradation processes. First, a multi-technique approach was developed based on the CHARISMA European infrastructure and was applied to a selection of decors from different countries and periods. More recently, from 2014 to 2016, two research projects, CORDOBA and CORD’ARGENT funded by the French foundation PATRIMA took place in France to pursue the work on specific aspects.

The CORDOBA project, coordinated by the research center for conservation (CRC, in Paris) in collaboration with the C2RMF (Paris), the National Renaissance museum (Ecouen), a freelance leather conservator (C. Bonnot-Diconne) and an art historian (J.-P. Fournet) funded a postdoctoral contract (M. Radepont) for one year from October 2014. The project focused on the characterization of the silver foil by non-invasive ion beam analyses. This combines analyses by PIXE (Particle Induced X-ray Emission) to characterize the silver foil composition and RBS (Rutherford Backscattering Spectrometry) to measure the foil thickness. As part of the project, model gilt leather samples were prepared according to an 18th century recipe and used to optimize the analytical methodology. Then a corpus of over 50 historical samples originating from different geographic areas in Europe was analyzed by the techniques cited above. In October 2015, a study day on gilt leather was organized at the National museum of Renaissance in Ecouen as a conclusion of the CORDOBA project. That day, that gathered around 70 persons, included presentations from art historians, conservators, curators and scientists, who provided different views on these decors, followed by presentations of the results gained through the research project. The publications of all the data are in progress.

The subsequent CORD’ARGENT project, which started in October 2015, focused on the tarnishing of silver leaves in gilt leather decors. For this project, the Lavoisier Institute from the university ‘Saint Quentin en Yvelines’ joined the team to provide an expertise on metal foil properties. Silver tarnishing on gilt leather decorations is commonly observed, generally localized, and, in extreme situations, total blackening of silvered areas can occur. Consequences are important as it affects their readability and finally many of these objects are left in storage. In some cases this degradation may be related to past conservation interventions. Consequently, the impact of maintenance and conservation treatment on gilt leather and particularly on the silver leaves is questioned, nevertheless the question of silver tarnish in gilt leather has little been investigated. For that reason the CORD’ARGENT research explored the role of the materials and environment interacting with the silver leaf, considering two steps in the life of these decors: the manufacture and the maintenance, including conservation. In the project, new analytical techniques were implemented to answer the different questions raised by the study, such as atomic absorption spectroscopy (AAS), field emission gun scanning electron microscopy (FEG-SEM), electron backscattered diffraction (EBSD), X-ray fluorescence (XRF), pyrolysis gas chromatography-mass spectrometry (GC-MS). The project provided many new information on these decors regarding the impact of the manufacturing, the environment and the conservation on silver tarnishing in gilt leather. These results will be presented at the ICOM-CC triennial conference in Copenhagen in September 2017.

Project partners:

-    Conservation of Gilt Leather (France): Céline Bonnot-Diconne, Conservator
-    Instituto Superiore per la Conservazione ed il Restauro (ISCR, Rome, Italy): Mariabianca Paris, conservator and Marcella Ioele, Heritage scientist
-    C2RMF (Paris, France): Claire Pacheco, Heritage scientist
-    Specialist of Gilt Leathers (Paris, France): Pierre Fournet, Art Historian
-    CRC - USR 3224 (Paris, France): Laurianne Robinet, Heritage scientist