This research aims to characterize and compare the protective behaviour of a bio-based treatment versus benzotriazole (BTA) for the preservation of copper-based artefacts affected by active corrosion induced by copper chlorides. For this, the treatments were applied on artificial copper hydroxychlorides produced on copper sample. Their inhibition performance was then investigated by Scanning Electron Microscopy, Infrared Spectroscopy and Electrochemical Impedance Spectroscopy. Results showed few BTA-Cu complexes formed and poor protectiveness of the BTA treatments. In contrast, the bio-based treatment resulted in the conversion of almost all copper hydroxychlorides into copper oxalates, providing a more efficient corrosion inhibition.

The paper reports the study of five totalizing counters preserved in the collections of the CNAM (museum of the French National Conservatory of Arts and Crafts) in Paris. These artefacts are part of a corpus of over forty counters attributed to the Darras company founded by engineer Alphonse Darras (1860-1936). In the framework of the LacCA project at Haute Ecole Arc, Neuchâtel (Switzerland), dedicated to the characterization of lacquered copper-alloys, our attention was drawn to the different aspects of the object’s coatings. Lacquers were frequently applied to technical objects to both protect them from corrosion and provide an esthetical appearance. Five totalizing counters showing various typologies and surface colours were chosen from the set and explored by a non-invasive multi analytical approach. The comparative study – investigating lacquering processes and materials - contributes to the historical study of these artefacts.

The application of varnishes on the surface of metal objects has been a very common practice since antiquity, both for protective and aesthetic purposes. One specific case concerns the use of tinted varnishes on copper alloys in order to mimic gilding. This practice, especially flourishing in the 19th century for scientific instruments, decorative objects, and liturgical items, results in large museum collections of varnished copper alloys that need to be preserved. One of the main challenges for conservators and restorers deals with the identification of the varnishes through non-invasive and affordable analytical techniques. We hereby present the experimental methodology developed in the framework of the LacCA and VERILOR projects at the Haute École ARC of Neuchâtel for the identification of gold varnishes on brass. After extensive documentary research and analytical campaigns on varnished museum objects, various historic shellac-based varnishes were created and applied by different methods on a range of brass substrates with different finishes. The samples were then characterized by UV imaging and infrared spectroscopy before and after artificial ageing. The comparative study of these two techniques was performed for different thicknesses of the same varnish and for different shellac grades in order to implement an identification methodology based on simple non-invasive examination and analytical tools, which are accessible to conservators.

Gold lacquers on ornamental bronze pieces: actors, practices and markets in Paris during the 19th centuryJulie Schröter Thèse : références bibliographiques Julie SCHRÖTER, Les vernis or sur les bronzes d'ameublement : acteurs, pratiques et marchés à Paris, Université Paris 1 Panthéon-Sorbonne, soutenue le 4 décembre 2021, un volume de texte (534 p.) -un volume d'annexes (176 p.

Cet article présente l’un des protocoles de nettoyage des bronzes dorés encrassés et ternis actuellement employés au C2RMF. Les avantages et limitations possibles du procédé sont évoqués à partir d’observations directement menées sur des œuvres, ainsi qu’à partir de tests comparatifs simples effectués en atelier sur des coupons métalliques. Si les résultats obtenus permettent d’affiner les paramètres les plus adaptés en termes d’innocuité vis-à-vis des bronzes dorés, ce premier constat ouvre la perspective sur une étude plus approfondie prenant en compte d’autres variables et modes d’évaluation. Enfin, des améliorations de l’appareillage utilisé sont proposées afin d’assurer un meilleur contrôle du processus de nettoyage par le conservateur-restaurateur.