An unexpected surface: Research and treatment of a 19th century mounted oyster shell by Froment-Meurice

Emily Brown

Abstract

An oyster shell set into a delicate gold, silver, and gilt-silver metal mount belonging to the Walters Art Museum required treatment. Made in the late 1870s in Paris by the celebrated goldsmith firm Froment-Meurice, the object was damaged and heavily tarnished. Analytical testing and literature research  indicated that the silver components might, in part, contain an originally applied patination layer (oxidized silver or argent noir). Since  intentionally patinated silver surfaces are rare in museum collections and literature resources are scarce, it was decided not to polish the silver components, while the object would be cleaned overall and tarnish reduced only on the gilt-silver and gold components. After careful testing, an acidified thiourea solution made with sulfuric acid and gelled with xanthan gum was used to  reduce the tarnish on the delicate gold and gilt-silver components. The formulation of the gel allowed for an extremely controlled application, and treatment resulted in a bright, shiny surface for the gilt-silver and gold metal, which required no additional buffing or polishing. The intent of this article is twofold: first, it will present current research, resources, and further avenues to investigate oxidized silver within the context of the Froment-Meurice workshop; second, it will describe an efficient, controlled method to chemically reduce tarnish on delicate gold and gilt-silver surfaces.

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