Helen M. Thomas-Haney and Xsusha Flandro discussed their research and investigation of restoring aluminum finishes at a train station. Discovered in 1825 by Hans Christian Oersted, aluminum was used in jewelry and decorations into the mid-nineteenth century. The first architectural use of aluminum in the United States was for the cap of the Washington Monument in 1884. As production increased and price decreased, aluminum began to be more widely used in commercially available products. By the 1920s, aluminum was being used on many buildings in Vienna, in modernist movement buildings, and on the Empire State Building. Companies such as ALCOA Aluminum advertised aluminum as weather resistant and structurally sound. It’s ease of being manipulated made aluminum popular as decorative ornamentation on exteriors, but also in Art Deco interiors.
Built in 1932, the train station was constructed of a copper roof, pine ceiling, and aluminum arch spandrels. The station had alterations over the years, including lead paint, the addition of billboards that pierced the aluminum panels, and graffiti. The conservation project began with research into project specifications, original drawings, and original finish specifications. Through research and material evidence, it was clear that the aluminum spandrels had three different types of mechanical finishes. Based on the historical terminology, these were identified as “satin”, “sand-blasted”, and “sand-blasted deplated”. The station remained in service during the restoration, so precautions were taken during paint removal and repair work. After the paint was removed, two different types of corrosion were revealed. Corrosion was especially significant in areas where the differing materials joined. Based on the containment issues caused by sandblasting to remove corrosion, other means of removal were necessary. Some corroded areas were patched and repaired, while other panels were taken offsite for restoration.
After surface preparation, the finishes were recreated in-situ. The “satin” finish was recreated by hand sanding with a coating to prevent corrosion. Initially, a bristle-blaster was used for the “sand-blasted” finish, but it did not complete the desired effect. The team later used aluminum oxide blasting for the finish. The “sand-blasted deplated” finish was completed with an aluminum patination process with a black patina buffed to gray.
With just a day between the ground breaking ceremony at the San Francisco Museum of Modern Art (SFMOMA) and the 2013 AIC conference, panelists Ruth Berson, Craig Dykers, Jill Sterett, and Sam Anderson once again came together to discuss the debates and collaborations that resulted in the “generous, magnetic, and transformative” design for the SFMOMA expansion. Each of the panelists were representative of the variety of programs and interests that had to be addressed in a project of this scale. This project began with generosity of the Fisher family of San Francisco. The institutional history of the SFMOMA was an important consideration before beginning to search for project architects. The SFMOMA had humble beginnings on the fourth floor of the War Memorial Veterans building. As it developed its own collection, the SFMOMA out grew the 1935 beaux arts building and needed it own dedicated building. In 1988 Mario Botta was selected to design the new building. Within fifteen years, the museum had brought in the Fisher collection and expanded its own holdings leading to the need for additional space. The new building on Third Street opened in 1995, marking the 60th anniversary of the museum.
Due to open in 2016, the expansion will add 235,000 square feet to the SFMOMA complex and will “seamlessly join the existing Mario Botta-designed building with a new addition.” The project will more add more than 6 times the current public space. There is also offsite storage for the museums expanded collection.
Ruth Berson, SFMOMA staff member and Deputy Museum Director for Curatorial Affairs, began the discussion with “Why expand-‘Why Between the What'”. Ruth participated in the design by contributing to the space planning and design development process. The planning process included an international search for architects,capital campaign, and the identification of the design intent. First priorities were Magnetic, Transformative, and Generous. Secondary words were added as guiding principles: Open, Distinctive, and Passionate. All of the priorities and principles led to a design that was artist centric, collection driven, and civic minded. In efforts to remain artist centric, artists were sometimes contacted to discuss the space. The new design used the guiding principles by expanding the program to include white space for events, performance art, and meetings. Technological advances were made to enhance the visitor experience, while also being mindful of the uniqueness of the collection and its unique holdings. Another goal was to meet LEED expectations and expanding the museums education programs. After the SnOhetta was selected as the architect a collaborative conversation took place between Craig Dykers and Mario Bota. Bota stated that “I had my moment with the building, now it is SnoHetta’s turn………I will withhold my opinions until after it is finished.”
Craig Dykers, Principal of SnOhetta Architects, continued the discussion with the “SnOhetta Response”. Craig reiterated the importance of the institutional history to the design process and added that architects were not selected based off of a proposed design. It was a selection process based on the architects knowledge of the SFMOMA. The building is surrounded by six to seven streets with turn of the century buildings. Based on the design priorities, SnOhetta wished to activate these areas with new entrances and to add a public collection space with an open area for free public access. This new “art court” will also serve as a transition space between neighborhood and the building. It was important to the design team to balance the traditional and new buildings that surround the SFMOMA. Machines and daylighting systems were integrated into the design to protect and enhance the museum collection. The facades of the new building were modeled off of the quality of light and rippling water that is unique to San Francisco. With each step in the design process, SnOhetta remained mindful of the priorities and guiding principles to establish continuity to the overall design.
Jill Sterett, SFMOMA staff member and Director of Collections and Conservation, discussed the use of “Collections as a Directive” in the design process. Jill explained that the team took cues from the Public, Education, and San Francisco itself in order to inform their decisions. The artists and the relationships that they keep with them are the center of the SFMOMA. It was important that the new offsite storage facility is a dynamic space. The new space will have capacity for collection study, research, photography, carpentry, packing/crating, and big sculpture conservation. These stipulations required the team to reframe the question of how to activate the collection in two different spaces. The expansion/new building will be divided into storage, public space, conservation, and staff areas. The lower levels will hold the support and collection areas-this is conceived as a dynamic storage area and not static. It will be viewed as a n operating set of suites. Throughout the new zones, the initiatives and priorities will act as directives for accomplishing the project goals.
Sam Anderson, Principal of Samuel Anderson Architects, wrapped up the discussion with “Engagement of Specialized Areas Integrated into the Overall Plan”. Sam added that the mechanical systems had to respond to the climate and the program. It was important that these strategies were specifically designed for each circumstance. With such dynamic spaces, it became a question of how to fit multiple and growing functions into one program design. The permanent photography collection will be stored on-site, but the lower levels of the building will also serve as transient art storage. In addition to addressing the on-site storage needs, it was important to plan for areas for staging and mounting. In response to the climatic considerations, it was a priority to address the potential for seismic activity. The solution for the concerns had to also be functional within the program of the building. Each individual off-stage space was is therefore integrated with the next, for instance the conservation labs are integrated through a vertical visual connection.
In all aspects of the design, it was important to maintain collaboration between the architects, designers, and museum staff in order to address the clearly identified priorities and guiding principles of the museum. As the work progresses towards a completion goal of 2016, the two year preparation and planning period was integral to the success of the SFMOMA expansion.
In addition to Rose Cull’s presentation on contacting the contemporary artist, or not, is a single case study by Tad Fallon. The object in question is a “Kosode” form cabinet titled “Meet Mr. Chips” by the California furniture maker, John Cederquist. I encourage everyone to check the website for images of other Kosode cabinets.
The cabinet is one of a series made of mixed woods, aniline dyes and epoxy resin and was completed in 2006. The owner had purchased it directly from a gallery exhibition. Displayed in a bright and sunny room in Connecticut, the highly decorated façade of the cabinet had faded dramatically, and the owner contacted Fallon and Wilkinson to have them treat it. The owner did not want to send it back to the artist for restoration.
Tad began the project with background research and then contacted John Cederquist directly. John was interested and friendly, and the conversation led to a visit by Tad to the artist’s studio. During the visit, Tad was given an in-depth tour by the artists assistant Chris Labont, and was able to take extensive notes and photographs of the artists materials, techniques and tools, enough to completely recreate the work from scratch.
However, the take-away was more complicated then that.
-From a conservators point of view, the materials and techniques were inherently problematic and prone to light damage.
-The large Kosode series techniques evolved over time and the techniques used at the end of the series were somewhat different from those used at the start.
-The range of materials available to the artist had changed over time, due to California VOC compliance.
-From the artist’s point of view, he had moved on, this was old work, and he was looking forward rather than back.
So what’s a conservator to do? The original work has faded and no longer resembles the original appearance or intent of the artist. The color and appearance cannot be “brought back” through intervention. The options are largely limited to:
- Leaving it alone.
- Creating a complete overlay from original materials on a reversible ground. (only marginally feasible)
- Restoring the façade completely using the artist original materials and techniques as recorded directly from the artist and artist’s assistant.
- Recreating the façade completely using improved materials that remain true to the original intent and appearance of the artist.
Not easy choices, not one of them. What would you do? I for one truly hope that Tad will be able to present “Take 3” next year!
This presentation summarized the collaborative research of the cleaning of acrylic paint films by the authors representing the DOW Chemical Company, the Tate Gallery and the Getty Conservation Institute. The aim of the research is to develop and educate professionals in the cleaning of complex, contemporary synthetic painting media. Early findings of this research have been presented at the AIC Annual Meetings in Los Angeles (2009) and Milwaukee (2010) and at the Cleaning 2010 Conference in Valencia. The components of these systems have varying effects on the medium: acrylic paint films are easily swollen in an aqueous environment, hydrocarbons have poor cleaning efficacy and on large colored surfaces there is a risk of tidelines. The surface character can be changed if extracts are removed.
Dynamic mechanical analysis of potential cleaning materials was conducted; the procedural process was described as “clamping” system that would provide uniform tension across the test film as it was dipped in solution. The displacement of the grips is measured as the paint film contracts upon drying. Acetone and water produced significant swelling, mineral spirits resulting in a flat line. Analysis was conducted using FTIR-ATR (Fourier transform infrared-attenuated total reflectance) spectroscopy on cleaning swabs indicating the level of surfactant material at the surface.
Trial microemulsion cleaning formulations were prepared by DOW and the Tate which were tested by conservators at workshops, including four CAP’s (Cleaning Acrylic Paintings) seminars presented in different cities by Chris Stravroudis. Resulting evaluations have contributed to further refinement of formulations for better compliance with performance criteria desired by conservators. Three classes of microemulsions were produced. All have an aliphatic hydrocarbon in a continuous phase. They incorporate different surfactants. The presence/level of an alcohol as a co-solvent is sometimes incorporated, as an alcohol is required in some systems to enable a stable microemulsion structure. One class of potentially useful formulations of water-in-oil microemulsion systems that are thermodynamically stable is being tested. They incorporate deionized water, a non-miscible hydrocarbon solvent (one being tested is hexanol/butanol (?)) and a surfactant in an attempt to remove grime without removing original material, namely surfactants used in the manufacture of these painting materials, which are known to migrate to the surface as they age. They offer the possibility of exploiting cleaning efficacy associated with aqueous systems but in a predominantly solvent environment where the micelles formed has the surfactant on the outside and the water on the inside. The pH in these systems can be varied using sodium chloride. The ionic strength of the solution should be compatible with the paint film; conductivity should be adjusted, as needed. A stable microemulsion will be clear, while an unstable one will be milky. Other components of the three series included a “green” surfactant, Ecosurf®, a promising new Triton material, Triton GR7, which is soluble in Shell Sol solvents, and the introduction by Richard Wolbers of silicon based cleaners. The latter material was reviewed by Chris Stravroudis in his article, “More from CAPS3: Surfactants, silicone-based solvents, and microemulsions”, WAAC Newsletter 34/3 (Sept 2012), pp 24-27.
The series of microemulsions are being extensively tested including the issue of clearance. A new publication on the progress of this research is expected in 2014.
I had really been looking forward to this presentation, especially as there were two WAG session presentations on the same topic, and Rose did not disappoint.
Rose began her presentation with some solid background information and began by defining contemporary art as being created by living artists, meaning I believe that the artist and viewer (and in this case the conservator) are both living at the time the art is being viewed. She also reminded the audience that the creation of art has changed from a means of expression based on a solid craft background to a means of expression where issues of stability or longevity may be of little or no concern. As the inherent instability of much contemporary art requires intervention to maintain some degree of the artist’s original intent over time, this lead to a short overview of the Visual Artist Rights Act (VARA) of 1990. The Act grants the moral right of artists to protect their works from derogatory treatment that may be prejudicial to the artist’s honor, reputation, or economic interests. (apologies for a very compressed overview of the Act which may be viewed in it’s entirety on the web). Rose made a point of noting that under VARA an artist cannot claim conservation as a “destruction, distortion, or mutilation of their work unless it is performed with gross negligence”.
Through her past experience in interviewing various museum related stakeholders she made one other important point. A work of art represents a specific point in an artist’s development or career. Although one may communicate with a contemporary artist and ask those questions that seem most vital to know about a specific work, the artist may have moved on, changed his or her working methods and lost or forgotten the inspiration for a past project. An artist may not view a completed work from their past with the same interest or perception as when the work was fresh, and in fact might create the same work quite differently today.
With the background information clearly presented, Rose offered two case studies, one with a sculpture by Louise Nevelson, and one by Cornelia Parker.
With the Louise Nevelson sculpture, Rose read Nevelson’s autobiography, researched her materials, looked at other works, and contacted the Nevelson Foundation. The Foundation is run by Maria Nevelson, Louise’s granddaughter, and Maria contacted Rose directly, offering enthusiasm and support by sending along a list of conservators known to have treated other Nevelson works. Armed with knowledge, support, and the consultation of fellow conservators Rose was able to address the issues and complete the treatment to everyone’s satisfaction.
The Cornelia Parker treatment was a bit more complicated, beginning with the fact that it was created from charred wood collected from a church that had been struck by lightening and burned. In this case she did not contact the artist. Although the reasons for treatment were rather mundane, an accumulation of airborne dust was beginning to distract from the presentation, the questions and answers might have lead to complications (I am paraphrasing here). In the end Rose created a system of careful and effective non-contact “dusting” effectively minimizing intervention.
Perhaps the most disappointing part of the presentation was the limited time left for questions, with only enough time to register the opposing views from the audience that 1. artists and Foundations were often impossible to work with, and 2. times have changed and artists and Foundations are much more receptive. Wish that could have been batted about for another hour!
I have a fascination with plastics, I guess it’s partly because the array of materials that can be chemically engineered seems to have infinite possibilities. Objects of many textures, shapes, colors and applications exist because of plastics. Unfortunately, their existence creates challenges to both preservation and sustainability. As works of art or material culture, conservators want to make them last for as long as possible, but the most long-lived plastics also pose the problem of disposal. The types of plastics that are most likely to break down in the environment are also crumbling to bits on the shelves of collectors and institutions.
This year’s AIC meeting featured a workshop presented by Yvonne Shashoua and Thea van Oosten, two well-known experts in the field of plastics in museums. Shashoua’s book, Conservation of Plastics: Materials Science, Degradation and Preservation, is a good reference. Both Shashoua and van Oosten were part of the 2008 European POPART initiative, (Preservation of Plastic Artifacts in museum collections), which selected a few types of plastics used in artwork, studied their deterioration pathways, and possible methods for their preservation, cleaning and repair. http://www.bartlett.ucl.ac.uk/graduate/csh/research/projects/popart
To begin the workshop, we were presented with a historic overview of many types of plastic materials encountered in collections. From gutta percha to polyester we learned of the properties and uses of different polymers. Van Oosten had an entertaining way of categorizing plastic types by their properties into three snack food groups; gummy worm, chocolate bar, or cookie. Gummy worm plastics are in the elastomer category, which includes both natural and polyurethane rubber. These materials are stretchy and flexible at room temperature. Chocolate plastics are the thermoplastic category, which includes polyethylene. These materials polymerize through addition and can be melted and reformed into new shapes. Cookie plastics are in the thermosetting category, which includes Bakelite (phenol formaldehyde), melamine formaldehyde and Vulcanite. These plastics are formed by condensation reaction with water being lost, and they cannot be reformed into new shapes with heat.
We learned that it is important to know what type of plastic you have before you attempt any repairs, because an adhesive that might work with one polymer will dissolve another. To help determine the appropriate adhesive, one should consult the Hansen or Hildebrand solubility parameter for the given plastic. The strength of bond needed, the viscosity of the adhesive and the elasticity of the plastic are other factors to consider. For lightweight polyurethane foam, water based adhesives commonly used in conservation are often adequate. Clear plastics, like polystyrene or polyester may require consideration of the refractive index of the adhesive in order to make an invisible joint.
In the afternoon we split into two groups. We had time to experiment with adhering and mending a variety of plastics, and test cleaning cloths, pads and swabs for cleaning plastics. According to results obtained from the POPART study, it is important to clean plastics as soon as possible when they become soiled, since particles may migrate into the plastics and become impossible to remove in a few short weeks. At the same time a soft cleaning cloth must be used that won’t cause abrasion to the plastic being cleaned. My experiences in this workshop highlighted the importance of testing on mock-ups!
The four plastics at greatest risk of deterioration are cellulose nitrate, cellulose acetate, plasticized (flexible) polyvinyl chloride, rubbers, and foams. Cold storage is typically recommended for these materials. The leaders of this workshop also recommended use of an oxygen scavenger in encapsulated packaging for preservation of rubber. Rubber in collections is rapidly deteriorating by oxidation, which causes it to turn yellow and brittle.
Along with POPART a number of research projects have brought the needs of plastics collections into the spotlight in recent years; however, it is clear that more research on active conservation methods is necessary. There is so much more to learn about fascinating plastics!
This year’s Book and Paper Group tips session was truly impressive. The whole session was jam-packed with helpful hints and I found myself in frantic note taking mode, trying to record all of the great advice. In just over an hour, eleven “tippers” presented an array of useful descriptions of experiences, treatment methods, housing projects, and emergency preparedness information. Everyone had great visuals with photos and diagrams, physical examples to examine, and even take-away samples.
Several tips had emergency preparedness and response in mind. First, we learned of Laura McCann’s experience with the flooding in NYC as a result of Hurricane Sandy. When the East River overflowed and completely submerged a medical library’s records storage, the materials were not accessible for weeks! The importance of prior planning was highlighted. When power is lacking, it is extremely useful to have headlamps and absolutely necessary to have your emergency plans accessible at home. Consideration of priority collections, BEFORE the stress of an emergency situation, was emphasized. Those in attendance were able to collect a sample of a TEK wipe, which is absorbent and reusable. Also on the topic of emergencies, Emily Rainwater explained how Karen Pavelka tested the effectiveness of polypropylene fiber pads for absorbing oil, a common contaminant in flood water. These pads attract oil, but repel water. Finally, Roberta Woodrick showed us how to creatively use hairpins to attach Colorplast awnings as a shield for library shelving in areas with recurring leaks. She had also built a mobile humidity chamber of ¼”acrylic sheet and furniture movers with wheels, in order to humidify large architectural drawings.
There was a presentation on lead white reversion by Amy Hughes, which lead to some interesting commentary and discussion of the mixed results several conservators had experienced when trying to reduce the discoloration of lead white pigments. As might be expected of an oxidation-reduction reaction, hydrogen peroxide treatment to improve discolored lead pigment may be temporary. There was suggestion that inpainting over discolored lead white is a viable option that should be considered. In any case, it seems important that conservators communicate the reactivity of lead white to clients and curators to warn of possible changes after treatment.
For reducing mineral deposits on paper, Karen Dabney demonstrated how “huffing” into a beaker of deionized water produced an effective solution of carbonic acid (pH 4). Her before and after images revealed just how effective this could be, but be careful not to hyperventilate if you try this yourself!
Judy Walsh was not present, but she created some impressive diagrams of a method of creating a cheap and effective suction disk for treating individual book pages, while still bound.
Renate Mesmer provided some examples of neatly engineered storage enclosures for a hanging wax seal and a sliding tray for a vellum manuscript broken in half, inspired by the mechanics of a pop-up book. She also had a video of how a hot air gun can magically correct errors in folds and angles when making book exhibit supports of Vivak (clear thermoplastic sheet of polyethylene terephthalate). http://www.professionalplastics.com/VIVAKPETGSHEET
These were some, but not all, of the tips we heard this year from BPG members. Thanks to all of the tips contributors; Shelly Smith, Beth Doyle, Renate Mesmer, Karen Dabney, Deborah Rohan, Judy Walsh, Jamye Jamison, Karen Pavelka, Roberta Woodrick, Amy Hughes, and Laura McCann, and many thanks to Sarah Reidell for moderating.
Look for these tips and more, to be published in the next BPG Annual.
I wonder what Julia would think about the current state of her kitchenware? In Mary Coughlin’s talk, “Bon Appétit? Plastics in Julia Child’s Kitchen,” Mary discussed issues she and her Museum Studies class faced while inside the Julia Child Kitchen exhibition at the Smithsonian’s National Museum of American History (NMAH). Mary is an objects conservator and professor at George Washington University. Her class carried out a condition survey of the exhibition as it transitioned from its original installation into part of the new FOOD: Transforming the American Table, 1950-2000 exhibition.
The kitchen was originally located in Julia Child’s Cambridge, Massachusetts home from 1961 to 2001 and was the setting of her last three television shows. When Julia donated it to NMAH, the museum accessioned over 1,200 objects, ranging from spatulas to a Rubik’s Cube. The kitchen was installed in the museum as Bon Appétit! Julia Child’s Kitchen, a temporary exhibition that was probably only meant to be on display for less than one year. But as is often the case with well-loved exhibitions, it ended up being on display for a decade.
Mary’s class worked within the exhibition, actually in Julia’s kitchen on view to the public, as they carried out the condition survey. It seems as though many of the museum visitors also wished to step inside the kitchen, as Mary humorously noted that they often heard the thud of visitors walking into the glass partitions. In an effort to provide outreach to the public, a curator was posted outside the kitchen to discuss the project with visitors. In addition, the students wrote blog posts about their experiences which can be viewed on the NMAH’s blog “O Say Can You See?” (For example, see one student’s post here).
After the condition survey, the class made recommendations for ways to incorporate preventive conservation into the new exhibition. Two of the main problems encountered in the old exhibition were dust and degraded plastics. The old exhibition did not have a ceiling, and the vents above the kitchen created a significant dust problem. This issue was particularly problematic considering that many of the plastics within the kitchen are oozing and sticky. The new installation is sealed on the top, and during Mary’s evaluation of the new exhibition six months later, she found a significant decrease in dust accumulation. One problem area was a large gap around one of the glass door covers, but it has since been gasketed to create a better seal.
Mary’s class also found evidence of fading and discoloration in plastics. For instance, the top surfaces of a set of rubber kitchen gloves had turned black, while the undersides remained blue. Mary placed mylar barriers underneath and between problematic plastics to prevent sticking and oozing on surrounding objects. And when the gloves were reinstalled in the new exhibition, the top glove was flipped in order to display the blue side, following the request of the curator.
Mary mentioned the curator’s desire for authenticity within the exhibition and that they wished to have all the original objects on display within the kitchen. While Mary’s class found evidence of plastic degradation, the museum continues to display the degrading plastics in a relatively similar environment as the previous exhibition (although the HVAC system is improved and dust is being mitigated. She also noted that the degrading objects were not causing damage to other objects). Mary’s talk raised questions that many museums and conservators must face, such as authenticity versus preservation? Does displaying original degraded objects or surrogate objects in good condition change the meaning or importance of the work? The answers to these questions may also be different within the context of a history museum as opposed to an art museum.
As I viewed images of oozing spatulas that are not dissimilar to those sold today, one of the questions I had (but didn’t get a chance to ask Mary) is whether there was any discussion with the curators about purchasing surrogate objects either to be displayed now or in the future? Maybe similar objects could be purchased now, while they are still readily available, and stored in more optimal conditions (dark, cold storage?) to be displayed later if needed.
I can’t help but wonder, what will the plastics in the exhibition look like in another ten years? And what would Julia Child think? Bon Appétit?
The inaugural meeting for this group took place on May 31, 2013 at the AIC Annual Meeting in Indianapolis, ID. Organized by Nancy Ash, Scott Homolka, Stephanie Lussier and Eliza Spaulding, the session presented the Draft Guidelines for Descriptive Terminology for Works of Art on Paper which is a project under way at the Philadelphia Museum of Art and supported by an IMLS 21st Century Museum Professionals Grant.
Continue reading “AIC's 41st Annual Meeting- Art on Paper Discussion Group”
For me, this presentation was one of the high points of the conference – a thoughtful re-examination of a typically undertaken protocol.
The Winterthur Museum collection of silver numbers around 11,600 and over 2,000 of those pieces are on display in period rooms and galleries at the museum. Indeed, as characterized by Bruno Poliot, this is a massive task. To reduce wear and handling, silversmith and then conservator Don Heller began a program of cleaning then coating silver in 1974. After a period of experimentation, Don chose to use Agateen Air Dry Lacquer #27, a cellulose nitrate, for coating, suggesting that it should be replaced every 10 years but could last up to 28 years in a museum environment with careful handling. Over 1000 silver objects were thus treated between 1982-1987. While the conservators at Winterthur experimented other coating materials, including Acryloid B-72 and Acryloid B-48N in the decade that followed, research undertaken by conservation scientist Chandra Reedy and others, presented in the OSG Specialty Group at the 1999 AIC annual meeting, indicated that cellulose nitrate prevented tarnish better than acrylic resins, and Agateen #27 became the only lacquer used for silver at Winterthur from 1997 onward.
In 2009, the collection on display was surveyed systematically to assess the condition of the lacquer coatings. They found that:
- the lacquer on 42% of the objects had moderate to major problems and would require cleaning and re-lacquering
- condition of the coating did not directly correlate with age, method of application, or composition of the silver alloy
- condition of the coating did correlation with how well the lacquer was applied and the complexity of the object’s surface
- the degree to which the coating had yellowed was difficult to assess, but it was found along with tarnish
In 2011, the museum received a 2 year grant from IMLS for a re-lacquering project. The objects to be treated were grouped into one of three categories:
- objects treated in 1985 or earlier,
- those with coatings which were defective or otherwise failing,
- objects which had never been lacquered before. These were often complex.
Procedures for re-treatment were standardized in order to reduce the amount of application defects. Two conservation assistants were hired for the project, and they underwent a two month training program, working on simpler objects before moving on to more complex ones. Bruno did go into a fair amount of detail about the treatment procedures, and I’m sure his paper will also explore those in greater depth than I will here. One key feature of their procedure is examination one hour and then again 24 hours after application of the lacquer to look for imperfections and iridescence, which would indicate that the coating is too thin. Then a final examination of groups of objects is undertaken 2-3 weeks after the lacquer has been applied to ensure that all solvent has evaporated out of the film and to ensure that the coating is free of defects. Touch-ups to the coating can then still be done, and this period allows enough time for the solvent to completely evaporate, ensuring that it is safe to return them to display.
The team also investigated how Agateen #27 ages, looking both at objects coated with the lacquer in Winterthur’s collection as well as from the collections of two individuals who kept their pieces in home environments. The coatings on the pieces from the private collections exhibited a particular pinkish-brown discoloration, not found on any of the museum pieces. Though analysis of degraded coatings with FTIR and XRF and SEM-EDS provided information about the breakdown of the nitrocellulose polymer and elements found within the degraded films, it was the results of Time of Flight-Secondary Ion Mass Spectroscopy (TOF-SIMS), used to further characterize corrosion within degraded nitrocellulose films, that provided some unexpected results.
In TOF-SIMS, a high energy primary ion beam bombards a sample to ionize molecules on the sample surface. These ionized molecules are then characterized using mass spectroscopy. Looking at the lacquer films from the silver from the private collections, silver sulfide, silver oxides, silver chloride, silver sulfate, sulfate anion and silver cyanide were identified. Except for silver cyanide, all of these corrosion products were also identified in tarnish and corrosion products on uncoated silver.
Bruno pointed out that silver cyanide ranges in appearance from colorless to grey-white in color but could result in the pink-brown color noted in the lacquered objects if mixed with cuprite, which is another corrosion product found on silver objects due to a low copper content. They will next determine whether silver cyanide remains on the silver once the degraded lacquer has been removed and whether this corrosion product is detrimental to the silver.
This pink-brown discoloration was the topic of discussion following the talk. One conservator noted that she had also encountered this condition on lacquered silver from a private collection, and that the condition re-occurred within a few months following re-treatment. She mentioned that Agate, the company which produces Agateen, suggested that this might be a result of exposure to direct sunlight. Another conservator suggested that one potential source of cyanide might be a dip that was used in the past to plate or clean the silver, and that these dips may form complexes on the silver surface which may affect or react with a lacquer treatment. We need to look at how a past procedure may affect a current treatment.
Bruno concluded his presentations with a list of recommendations based on the 550 silver objects completed, and as the team at Winterthur contemplates re-lacquering 500 more pieces in 2015.
- The condition of nitrocellulose coatings on complex silver objects should be re-assessed every 5-10 years, given their finding that the majority of the coatings on complex silver objects failed within a 10-15 year time frame.
- When considering application of cellulose nitrate lacquers on silver, resources and time to maintain a silver lacquering program need to be considered as the time needed to remove and replace a cellulose nitrate lacquer is significant.
- Research into how degraded nitrocellulose lacquer affects silver needs to continue, as does finding alternative options for protecting silver against tarnish.