Winterthur Museum, Garden & Library has received a $110,759 grant from the Institute of Museum and Library Services (IMLS) for a project on preventive care for metal objects – protection that Winterthur deems its highest conservation treatment priority.
“Winterthur has a reputation for thorough research into conservation methods that influence international standards,” Winterthur Senior Objects Conservator Bruno Pouliot said in a press release. “We hope that our continued work on methods to prevent silver and copper alloys from tarnishing will continue that tradition.”
Museum officials said they were excited and honored to receive the grant, which would help the museum maintain its premier collection of American metalwork, made between 1650 and 1900.
To help the general public care for heirlooms, Winterthur conservators will share the best practices that result from this research through public programs. Related grant activities include the creation of a web video demonstrating silver care that will be available on Winterthur’s website and a two-hour class on silver maintenance as part of Winterthur’s Caring for Family Treasures series, the release said.
Two technicians will be hired to treat approximately 500 silver objects in the two-year project, which starts later this fall. They will remove failing lacquer coatings and apply new ones on silver objects, while Winterthur conservators and scientists study where a more aggressive corrosion was found, as well as different options to protect from tarnishing objects made of copper alloys.
Many of Winterthur’s silver and copper alloy objects are displayed out in the open as part of the interpretation of Henry Francis du Pont’s home. As a result, natural low-level sulfur pollutants in the air, alongside ambient moisture, cause tarnishing. Lacquer coatings remain for now a proven method to inhibit tarnish for up to 30 years within the museum environment, the release said.
Regular polishing, even with the gentlest methods, removes some metal, eventually erasing shallow elements of the design or, for silver-plated items, exposing the base metal underneath. Winterthur implemented a comprehensive metal-coating campaign in 1982, and this program has continued uninterrupted, although with some modifications. Since the 1980s, a lacquer based on cellulose nitrate has been used on most silver and copper alloy objects, as it provides the best balance of minimal visual intrusion, stability, and tarnish protection, the release said.
Following extensive condition surveys in 2009 and 2015, Winterthur assessed the performance of these coatings and made recommendations about their application and long-term performance. This information was shared through the conservation profession, influencing the decisions made by many institutions internationally regarding their own metal-coating programs.
The collection at Winterthur includes approximately 2,900 silver and silver-plated objects and slightly more than 2,050 copper, brass, and bronze objects. The metal on most is preserved in polished condition, reflecting the historically accurate appearance from centuries past.
The 2009 survey of the silver collection revealed widespread lacquer failure, caused either by aging coating, application defects, the presence of moving parts such as hinged lids, or the complexity of surface topography. The copper alloy survey in 2015 confirmed similar issues, but also a possible interaction between some coatings and the metals, requiring research before a new coating can be chosen, the release said.
Because of its uninterrupted history of protective lacquer coatings on silver and copper alloys and access to sophisticated instrumental analysis, Winterthur is uniquely positioned to conduct and disseminate this research. Resources will include Winterthur’s labs and scientists, as well as other scientific and analytical resources at the University of Delaware, the release said.