Life Cycle Assessment of Historical Silver Objects now on Public Display Part III of "Planning a Life Cycle Analysis Library of Preventive Conservation Methods"

By Sarah Nunberg posted 6 days ago

  

This is the third post about the activities of the FAIC project to plan for a Library of Preventive Conservation Life Cycle Analysis (LCA). The project is funded by the National Endowment for the Humanities through a Research & Development Grant, 2017-2018. The first post oriented you to the project and the second to Life Cycle Assessment (LINK). This post describes how the first of three LCAs was identified, designed, and completed. 

This article describes the research and results of an LCA conducted by Northeastern University students Wei Huang, Qiming Que, Kyle Varela, Milan Wilborn, Tianyu Yang, led by Professor Matthew Eckelman and Sarah Nunberg. Images and graphs provided by the students.

For all the LCAs in this planning project, the team prioritized activities that have relevance across the spectrum of exhibition, conservation, and resources common among our institutions. To jumpstart our thinking, we met in Boston to visit two very different institutions, The Gibson House museum and The Museum of Fine Arts, Boston (MFA). We talked with staff, toured the buildings, and had conversations about collections care and conservation interests and concerns. After some further conversation and a fortuitous connection to a project taking place at the Princeton University Art Museum (PUAM) we settled on three LCA projects.  

The first was an examination of three silver pieces, and their history of care and display at the two institutions we had visited and the PUAM. The pieces include a silver bowl given as a wedding present, a silver urn in a family collection, and the Liberty Bowl made by Paul Revere. The objects are similar in material and approximate manufacture period, but the organizations caring for them are quite different in size, available resources, and in the way they displayed and cared for the objects. This gave us the comparative opportunities we needed to make an assessment. 

Professor Matthew Eckelman, and his graduate students in the civil engineering course Life Cycle Assessment of Materials, Products, and Infrastructure at Northeastern University spent a semester researching the histories of the objects, including their time with the collecting institution, identified the materials and activities associated with the objects histories, used existing databases of environmental impact information, then drew their conclusion of the comparative impact. The LCA examined the cradle to now life cycle of the three objects. 

For each object the analysis had two distinct sections. The LCA explored first 

  • the impact of silver mining on the indigenous communities where mines were located
  • refining and processing the silver, including the impact of the mercury involved in production
  • transporting the silver
  • making the object
  • transporting and original housing of the object

Second, the LCA explored the period after acquisition: exhibiting and preserving the object in the institution. 

The students’ research into 16th, 17th, and 18th century mining, milling, and transportation was detailed and significant, monitoring energy consumption by miners, silver mill laborers, and the silversmith himself. They assessed transportation by ship, horse-drawn carriage, and automobile, depending upon the object. For our purposes, the second part of the LCA is the most applicable: energy expenditure for displaying and caring for the object. First, here is a quick recap of the sites and the objects as mentioned in earlier blogs, and then the results of the LCA.

The sites and objects

The Sons of Liberty Bowl (1786) is at the MFA Boston, one of the largest museums in the United States. The museum acquired the bowl in 1949. It has never traveled outside the Commonwealth and has never been loaned from the MFA. It is always on display in the Americas collection, which is now housed in one of the MFA’s newest galleries. The bowl is displayed in a Goppion exhibition case with RHapid Silica Gel and Zorflex to stabilize relative humidity inside. The gallery where it is housed is maintained with controlled relative humidity and temperature. The museum conservators do not polish the vessel, relying on environmental management to reduce tarnishing as much as possible.

The Gorham silver bowl that was an engagement gift to Rosamond Warren Gibson in 1871 is housed at The Gibson House Museum, also in Boston. The building is open today as a traditional historic house museum containing a collection of domestic and artistic artifacts. The site became a museum in 1957 after the death of the last family occupant. In 2001 the structure was designated a National Historic Landmark since the 1860 brownstone was one of the first of Back Bay Boston’s classic four-storey homes. The house is maintained by three part-time staff. There is heating and cooling, but no specific environmental management plan. The staff keeps the windows closed to reduce pollution infiltration from its high-traffic urban location. The bowl is exhibited on a side table in the dining room, and occasionally rotated to inside a half-round display case as you might expect to see in a home of this period. The objects on display have minimal security. Institutional resources are limited. The bowl is polished about once a year.

The third object in the LCA is the Lowell silver sugar urn (1790) usually displayed at the Morven Museum in Princeton. It is part of the PUAM collection of 97,000 objects, and is included in the exhibit, Nature’s Nation, curated by the American Department of Decorative Arts and Princeton students, which reflects the effect that the environment has had on American art from Native Americans to contemporary artists. The work concerning the silver urn explores the environmental implications of an exhibit, encompassing the impact of a work of art from creation to museum acquisition. The Lowell Urn is kept on a table on exhibit at the Morven Museum. It was treated in 2006, polished and coated with Incralac to prevent further tarnishing. 

The history and care for each of the three objects studied in this LCA differs according to the needs and resources of each institution where they are housed.  The Gorham bowl is housed in a bare bones institution with regular polishing, and no environmental management.  The Revere bowl exhibition is completely the opposite extreme; it has a state-of-the art microenvironment, overall environmental management, and high security. The Lowell urn is in the middle, housed in a building with some successful environmental management and, although it is displayed on a side table that is accessible to the public, the security system is more extensive than the Gibson house but much less than the MFA.

The assessment process

The students used the following conditions for comparison in their analysis:

  • The Gibson bowl is kept without any climate management, and cleaned and polished every three years.

  • The Sons of Liberty bowl is housed an enclosed microenvironment of a glass and powder-coated steel case with Rhapid Silica Gel and Zorflex replaced once a year.  The case is exhibited in galleries with climate control. 

  • While the Lowell sugar urn is usually housed in the Morvan Museum, during 2018-2019 it will be exhibited at the Princeton University Art Museum. For consistency in this study, the case and environment were calculated according to museum standards, the same as the MFA Revere bowl, including a climate-controlled space and an enclosed in microenvironment of a glass and powder-coated steel case with Rhapid Silica Gel and Zorflex replaced once a year. 

The LCA report said “For the energy use in conservation, main components considered were quantities of each product used for silver objects [polishing and coating, and building the exhibit cases], frequency of maintenance, and energy use for storage. This study investigated main ingredients of the conservation products from their instructions and material safety data sheets. These related ingredients, materials, and corresponding embodied energy were found in the LCIA Database… For each step of conservation treatments, the amount of each product applied to the silver object was assumed. As for the RH control, the amounts of RHapid Silica Gel and Zorflex were calculated using manufacturer instructions. Recommended quantity of silica gel for maintenance-free exhibit cases was 4 kg/m3.” 

Here are the components of the public use stage:

 

Because energy use was the focus of this impact study, the students conducted detailed assessment of the energy used for making the materials to polish and coat the art objects, build the exhibition cases, and condition the spaces where they are displayed. They discovered that the energy consumption for creating Goppion Outer Casing varied according to the material used for construction; the powder coated steel requires more than four times the amount of electricity and over 20 times the amount of heat to produce than then flat glass. The RHapid Silica gel requires significantly less energy for use of the product than Zorflex and the highest energy use in the polishing system when considering Wright’s Silver Cream and Microfibre Cloth is attributed to the cloth. To maintain the art object, the coating and cleaning materials such as Rohm and Haas Acryloid, acetone and ethanol require insignificant amounts of energy for use. (Note that this does not take into account toxicity or climate change indices). 

Here are the complete energy results:

pastedGraphic.png

Conclusions 

The students determined that the energy expenditure for the creation and early life of each of the three items had far less environmental impact than for the public life of the objects, and that the continuing energy expenditure was much less for the silver bowl displayed at the Gibson House Museum without the funds and staff to run environmental management systems.  The energy use for exhibition of the Lowell urn and the Revere bowl were nearly the same based on the highly managed exhibition rooms and display cases. 

 

Caring for the silver items included at times polishing, coating, and highly-managed microclimates and gallery settings. Without employing environmental management or any preventive conservation, the Gibson Museum bowl consumes far less energy in its lifetime compared to the two items in cases. However, because it tarnishes due to the lack of preventive measures, it requires frequent polishing. The abrasion of each polishing reduces surface decoration, often leaves residue, and easily scratches the surface. The bowl is maintained at a lower energy cost but a higher preservation cost. An Incralac coating (as on the Lowell urn) offers an option for reducing polishing while keeping the object on display without any environmental management.  

At the MFA and PUAM, and many similar institutions, best practices emphasize environmental management and minimal treatment. This is the case with the silver objects. However, the impacts of energy intensive environmental management on the natural environment are greater than the less-intensive approach of minimal to no environmental management with regular invasive treatment. The results demonstrate how LCA can uncover unexpected hot spots (areas of greater environmental impact) and can challenge assumptions.  In the silver LCA study, the benefit from environmental management for the object are so great that choosing the treatment option, although it results in lower environmental impact with less energy use, it is significantly less effective for preserving the object. 

So, the LCA identified the hotspots involved in public use of the art objects.  Now, they can explore more efficient sustainable practices, such as considering display cases made from materials that do not include powder coated steel, while still avoiding materials that off-gas and contribute to silver tarnish.

This LCA indicates that environmental management based on energy from nonrenewable resources presents significantly greater impact to the environment and is significantly less sustainable than treatment in this specific instance. The environmental impact of the Gibson bowl is negligible compared to the MFA and PUAM pieces because of the energy used for exhibition. The full report will be available in the FAIC LCA Library. ______

We would be delighted to hear from you with comments or questions, please contact us at snunberg@aol.com and sarah@sustainablemuseums.net 

In the next post we’ll describe LCA #2 a study of forty cleaning agents and five cleaning systems. 

This research project is funded by the National Endowment for the Humanities, Grant PR-253401-17, from the Division of Preservation and Access. Team Members: Eric Pourchot, FAIC; Sarah Nunberg, Objects Conservation Studio; Sarah Sutton, Sustainable Museums; Matthew Eckelman, PhD., Engineer, Northeastern University; Pamela Hatchfield, Museum of Fine Arts Boston; and Michael C. Henry, P.E. & AIA, Watson & Henry Associates. 


#Featured
1 comment
6 views

Permalink

Comments

2 days ago

I find this study, and others that provide comparative quantitative data on energy use for storage and exhibition really useful for sharpening my thinking on how best to evaluate the long term sustainability of preventive and interventive conservation methods. What I am left trying to imagine at the end of the post is what integrated monitoring, detection, intervention, deterioration management and documentation ecosystem and workflows might best slow rates of alteration and loss of remaining original tangible and intangible properties and characteristics in a collection of similar objects (my job), while accessing the greatest proportion of sustainable resources / consuming the least proportion of unsustainable resources? I guess I’m wondering if the authors would see that question as an accurate description of best outcomes or if I am framing the question in ways that miss other important variables, e.g. cost, per outcome unit of preservation over a sustained period of time?