As the title indicates this paper is the second part of a treatment that was discussed at last year’s session, and subsequently implimented during the past year. It brings up some fascinating and controversial issues and I admire Tad’s courage and boldness in presenting it to the profession. In short he totally refinished and recolored a work of art-furniture by a living artist.
I strongly encourage everyone, whether WAG or not to read the final paper because the detailed rational for the treatment are beyond what a humble first time blogger is capabable of re-iterating. The treatment was not casual and it is the thought and consideration that enlivens the context and makes this such a stimulating paper.
Tad’s treatment has created a different work of art. It is not the same as the original. The artist-applied colors and varnishes were first destroyed by UV light and the remnants removed by Tad. Tad then applied new colors by working with the artist. Although the resulting furnture is not exactly the same; it could be as close as anybody is ever going to get. He interviewed the artist and the artist assitant, he gathered the exact same materials, he learned the techniques of application (from the artist and otherwise) and documented everything. He also researched the effect of the treatment on the value of the piece which is something he can add to a treatment that few other furniture conservators can provide. He consulted with not only the owner of course, but with dealers as to the effect his treatment would have on value.
It is context that makes this paper so interesting. I would probably never do this treatment because in my lab and with the goals of my institution I would not be justified in such a radical intervention. But I am not allowed to talk to John Townsend, or Lockwood DeForest or any of the hundreds of annoymous workers that have made the furniture that I have treated. Even if I could, I doubt that I would listen to their advice without falling into professional funk.
I treat furniture to be placed in a historic house that is interpreted for the early 21st century viewer. That is my context. An example that occurred to me after Tad’s presentation was an 18th century French commode that I recently returned to a 19th century Gilded Age setting. Like any piece of marquetry furniture it had been stripped and sanded on a probably routine basis to restore the colors. (Not an option for Tad.) At some point the veneers became too thin for this practice to continue and, probably not coincidently, the standards of collectors have changed to accept the patina of age. It has been French polished to a whore’s shine, but still almost everyone that sees it thinks it is beautiful. It has sat in the same corner with everything else in the room for over 70 years. For me to even approach 50% of Tad’s intervention with this piece would be ridiculous.
Tad’s paper stimulated me to look at my own context and the assumptions that I bring to any treatment especially wooden furntiure. “It should suggest the artist’s intent but still show its age” – what exaxctly does that mean? It all depends on context. Now if I could just tone down some of these upholstery fabrics a little bit . . . Why is the context for a chair different than an upholstered chair seat?
Category: Specialty Sessions
Posts on talks that were presented as part of the specialty sessions at AIC’s Annual Meeting
42nd Annual Meeting – Architecture Session, 31 May, "Lime-Metakaolin Grouts for Conservation" by Norman Weiss
This technical talk discussed a new method and material for architectural conservation. Norman Weiss began by addressing the problems of lime grouts, and the nature of metakaolin. The problem of lime grouts is the anaerobic nature of the area the lime is being applied to, as the lime requires carbon dioxide from air for the setting phase of the lime cycle. Metakaolin is a class N pozzelan, a ‘thermally activated clay’, where dehydroxylation is accompanied by a loss of crystal structure. Metakaolin is between fumed silica (0.3 µm) and Portland cement (5 µm) in terms of particle size. Metakaolin is very quickly and specifically dehydroxylated between 500 and 530 degrees Celsius, a process which Weiss noted you “don’t have to finesse”.
Weiss continued by addressing the purpose of pozzelans within architectural conservation. The material must densify and fill gaps, must strengthen in order to create bonds, must reduce the amount of cement needed, and must reduce the amount of ‘bleed water’ in order to be the most desirable pozzelan possible. Metakaolin has the potential to achieve all of these goals, if used in a specific way.
This material has been previously looked at somewhat, the first study having been completed in 1993, and the commercial introduction of the material in 1994. Weiss also noted that there has been a lot of research into metakaolin as a grout in Portugal.
Metakaolin has a high water demand, and is not great for a grout, as it does not set well; in order to function, it requires a superplasticizer. Weiss and his colleagues have experimented with the reaction between lime and metakaolinite, which forms Straetlingite. What seemed to be the most important part of this talk was the discussion of the new methodology that Weiss and his colleagues have developed and patented using this material. The wall is mechanically stabilized, and the void is filled through a tube. This method gives the material the time necessary for the slow-strengthening material to achieve the necessary strength.
It will be interesting to see in the future the results of further study and case studies of completed projects using this material and methodology.
42nd Annual Meeting – Textiles Session, May 30, “In Consideration of the Thangka” by Denise Migdail
Any talk with the word “thangka” in the title is one I’m sure to attend. I’ve been hooked on these incredible graphic pieces since seeing one entitled “Protectress Riding a Zombie”. Because who couldn’t like an art form that depicts riding a zombie? So I was very happy to hear that Denise Migdail of San Francisco’s Asian Art Museum was giving a talk entitled, “In Consideration of the Thangka”. The meat of the presentation revolved around the method the Asian Art Museum has developed to store and display the 154 thangkas in their collection, which, I have to say, is very clever. But more about that later.
Denise began with a quick overview of what a thangka is: a Buddhist image used for meditation and/or teaching. Although most are painted, they can also be appliquéd, embroidered or even woven. Denise’s colleague, Jeff Durham, assistant curator of Himalayan Art, says that “thangka” translates to the highly technical term “flat thingy”. However, any conservator who has worked on one will tell you that’s an unfortunate misnomer.
The idea to revamp the storage system came with the 2000-2003 move of the museum from its former home in Golden Gate Park to its current home in the Civic Center. The museum received an NEH storage grant and decided that they wanted to eschew their previous hanging storage for flat storage because a) low-binder paint b) fragile silks and c) wooden hanging dowels. Although this project started before Denise’s arrival, she has been elemental in its development since she came on staff in 2006. She found from experience that the beautiful glass cases installed in the new museum were incredibly hard to access. Only one pane of glass could be moved at a time, allowing relatively small access points for objects that can get really, really big. The staff realized that the boards the thangkas were stored on would aid significantly in getting them into the case. So hey, why not keep them on the boards during display as well as storage? Many different types of mounting boards were experimented with, including Tycore, (takes up a lot of space and is pretty expensive), Coroplast (sharp edges and flexes a lot) and blue board, (still flexes, especially at large sizes). D-Lite boards were ultimately deemed the best option. Navy velveteen was originally selected as a show fabric for both its tooth and complementary color. The thangkas themselves were variously tied, pinned, or stitched to the boards. Eventually the decision was made to start using standard-sized boards because reusing is a great way to go green, and also to save money. Unfortunately, this meant that piercing the boards by tying the thangkas to them customized them too much. Since other rotations in the Asian’s galleries were currently being mounted with the aid of rare earth magnets, it was decided they would be a good solution for the thangkas too. Kimi Taira, employed at the Asian and writing an entry for the AIC objects wiki at this time (http://www.conservation-wiki.com/wiki/Magnet_Mounts), contributed much. The D-Lite boards translated well to magnet mounts, since they were rigid enough to support steel to attract the magnets. And since the gallery display was concurrently being updated, the navy velveteen was replaced with cotton flannel and a show-fabric surround. When a thangka had a bottom dowel, L and U hooks held to the board via magnets offered support.
Denise finished up her presentation by talking about some specific treatments they did on certain thangkas. The one I found most interesting was the recasting of a missing dowel knob. They made a RTV (room temperature vulcanized rubber) mold using the remaining dowel and cast a new one in resin, which was then painted. The end result was quite impressive.
At this time, the Asian Art Museum has three standard board sizes, with minor variations. Many thanks to Denise Migdail for sharing this great green solution with us! Look at this link to the Asian’s website for pictures and a great video clip: http://www.asianart.org/collections/magnet-mounts
42nd Annual Meeting, Textiles Session, May 29th: Analysis of Organic Dyes in Textiles by Direct Analysis in Real Time–Time-of-Flight Mass Spectrometry by Cathy Selvius-DeRoo, Ruth Ann Armitage
Direct Analysis in Real Time – Time of Flight Mass Spectrometry (DART-TOF) was shown to be a viable method of organic dye analysis in the presentation by Cathy Selvius-DeRoo. The beauty of the technique is that it requires only a small fiber sample, and no advanced preparation such as dye extraction, in order to get positive identification for a variety of dyes, both plant and insect based.
The project began with a grant to purchase the equipment. From there, various colorants were tested from a dye sample book, in order to develop the protocol. The sample was put in the ionizing gas airstream (helium) and heated to a temperature of 350 – 500 degrees. The result was fast and accurate identification of several dye classes, such as quinones, tannins and indigoids.
The presenter had a relaxed, personable style and shared some of her tips for success as well as lessons learned, including: better results were achieved with the higher temperature and with the addition of acid hydrolysis, which could be added just prior to putting the sample in the airstream using an eyedropper. The presenter confessed that flavonoids could be difficult to discern because the spectra are very similar for the various components.
After the method proved reliable, the technique was tested on textiles with undocumented dyes. The most satisfying was to substantiate family lore on a Civil War coat. The story was that a mother of a soldier dyed a Union issued coat to resemble a Confederate coat. Analysis revealed that the indigo was overdyed with Walnut (also referred to as Butternut). Cool.
Full disclosure – I signed up for blogging this talk because I’m a bit of a science junkie. I don’t always understand it, and in a small private practice, I certainly don’t have a Mass Spectrometer in the studio, but I appreciate knowing how to solve problems and who to go to for help.
42nd Annual Meeting – Case Studies in Sustainable Collection Care, May 30, “Becoming ‘Fit for Purpose’: A Sustainable and Viable Conservation Department at the British Library,” by Dr. Cordelia Rogerson
In this presentation, Dr. Cordelia Rogerson spoke about radical changes in the approach to treatment decision-making at the British Library under her direction as Head of Conservation. The changes in approach were sparked by deep cuts to the Library’s budget, resulting in a reduction of the number conservators working in the lab by half–from 70 conservators to 35. At the same time, there was increased demand for conservation work in the busy library where collections are constantly in use. These cuts forced conservators to evaluate the fundamental nature and purpose of their work to determine if they could do less treatment without compromising use of the Library’s collection.
In response, the British Library conservation department adopted a “fit for purpose” model to govern how much treatment to do for materials sent to the conservation lab. Items are evaluated to determine what treatment is absolutely necessary for the immediate projected use of the item, and only this necessary treatment is undertaken. “Vulnerable damage” (such as a long tear across a page) is likely to be repaired, while “stable damage” (such as a loss at the corner of a leaf that does not interfere with safe handling) will be left untreated in many cases. This represented a shift away from a previous emphasis on full (or more complete) treatment for the majority of the materials coming to the lab. The new model does still allow for high priority items and items selected for exhibition to receive treatment beyond stabilization.
After applying “fit for purpose” to seven discrete projects with positive results, the model was adopted as the guiding principle for all work in the lab. By doing only the work deemed necessary, the lab has greatly increased the number of repairs completed each year. At the same time, the efficiencies gained have actually allowed the conservators to devote more treatment time to high priority collections.
As one of only two conservators working in a lab for a medium-sized special collections, I found that many of the challenges, decisions, and compromises of the changing operations at the British Library sound familiar. I appreciated hearing how a “fit for purpose” decision-making structure works in the setting of one of the largest institutions of its kind and the dramatic impact it can have in cost-savings and efficiencies on this scale.
In the future, I would be interested to hear more discussion of “fit for purpose” decision-making in the conservation of library and archival collections, digging deeper into the diverse interpretations that might emerge for a range of materials in varied contexts.
42nd Annual Meeting, Paintings & Wooden Artifacts Joint Session, May 31, "Long Term Hygromechanical Monitoring of Panel Paintings," by Paolo Dionisi Vici
As a conservation student entering my first year of graduate study this fall, I was at first intimidated by the topic at hand and the thought of relaying this information to the conservation community, potentially including research scientists, techs, and seasoned conservators who may have a jump-start on understanding these concepts, their implementation, and design execution. However, Paolo Dionisi Vici’s presentation not only made the material pertinent and compelling, but also accessible to a layman like myself. I only hope I can do justice to the complexities of the issue.
The talk abstract provides a great summary as to the ‘why’ of hygromechanical monitoring of panel paintings. Mathematical models and theoretical systems regarding the short and long term effects of environmental conditions on objects need to be substantiated by real life data sets in order to move forward with our understanding of the impact of microclimates (and their fluctuations) on objects. This topic is in direct diologue with the conference theme, Conscientious Conservation: Sustainable Choices in Collection Care, and harkens back to the opening session talks broadly titled Exploring Sustainable Preservation Environments, in which the generally accepted environmental paramaters of the museum were discussed, questioned, and even at times directly challenged. Data-logging by experimental measures, as exemplified by Vici’s talk, is paramount to the future of this conversation.
Vici posed an excellent question at the beginning of his talk by asking “What does stability really mean?” As an example of the potential complexity of this issue, he refered to the localized monitoring of one of the viking ships in Oslo, in which different data responses were logged based on the instrumentations’ location on the ship. The abstract aptly states, “Due to the specificity of each artwork… the analysis of an artifact’s response… can supply useful information about its “individual” sensitivity to the exhibition microclimate….” As the viking ship demonstrates, the complexity of individual responses can even vary within a single (albeit enormous in this case) object.
Now to get to the nitty gritty of the talk, and the part where I formally apologize for my unavoidable oversimplication (of what I suspect Vici already drastically simplified) of the sophisticated instrumentation used to monitor panel paintings. I should mention that while this instrumentation can be used to monitor a variety of wooden objects (such as the viking ship), the abstract notes that “panel paintings are useful in representing the complexity of possible reactions.”
The system of monitoring, the Deformometric Kit (DK), employs two displacement transducers, attached perpendicularly to the grain of the wooden panel. Linear deformations in the panel can be measured based on the proportional change of length of the transducers and subsequent trigonometric calculations. The transducers can be mounted on the back of a panel in different configurations and are not visible while the object is on exhibition.
The DK has undergone several design modifications to improve the specificity of the data being collected and its practicality in a museum context. In earlier models, the transducers were screwed directly into the panels. This complicated the data, because the specifics of what was being measured (surface vs. interior deformations and fluctations) could not be determined. Improvements at the Metroplitan Museum of Art were tested, and the transducers were eventually glued to the surface of the panel. According to Vici, minor shifts in the mounting glue would not negatively reflect the recorded data, because the information being gathered between the two vertical elements reflects general, averaged fluctuations. A further improvement was made when the base of the system was split, with ‘clips’ being glued to the surface of the panel and the transducers then being attached to these clips, making the transducers removable for transportation of the panel.
Vici provided several examples of the DK in action. Simulations of the potential asymmetry of a panel’s surfaces were conducted by connecting transducers to both sides of test panels. The effects of the movement of moisture as it reached equilibrium within the panel could then be monitored. The data Vici shared with us from these trials spanned hundreds of days, and the applicability of this system’s monitoring to both short and long term condition fluctuations should not go unmentioned. The DK also assisted in inform conservators regarding the appropriate crosspieces needed to provide auxiliary support for a long crack running through The Annunciation, oil on wood, Peter Candid, 1585. The DK was able to assist in determining how rigid the cross pieces needed to be and what kind of connection to the panel would be most appropriate.
I would like to reiterate that Vici did an incredible job engaging the audience with what could have been a very esoteric topic. And, yes, while it could be said that this is AIC, and perhaps only we could be ‘enthusiastic about dust’ (a group of people of which I am proud to be among), I felt the room earnestly abuzz after his talk. One of the most important thoughts that I took away from this talk was the importance of empirical validation of theoretical modeling. It is this sort of empirical validation that will inform our decisions as conservators and museum specialists moving forward with the care of our collections.
42nd Annual Meeting – Paintings Session, May 29, 2014, "Oil Paintings on Metal Support: Study, Intervention, and Challenges" by Mónica Pérez
Mónica’s talk focused on the treatment of five oil paintings on meta at the National Center for Conservation and Restoration (Centro Nacional de Conservación y Restauración, or CNCR) in Santiago, Chile.
In 2012 five paintings from the Bernardo O’Higgins House Museum in Talca, Chile were brought to the CNCR in serious need of treatment. The paintings represented an exciting moment for the CNCR, since paintings on metal had not been treated there previously. One of the paintings was signed by Willem Van Herp, 1655, making it the oldest painting to be treated at the CNCR. All five of the paintings were bought in Europe in the 19th century by Eusebio Lillo (who also happens to have been the author of the Chilean national anthem) who donated his large collection of art to the museum upon his death in 1911.
Of the five paintings treated by the center, three were 21 x 29 inches, and two were much smaller, measuring 9 x 7 inches. Two had been previously cradled, and the rest were otherwise unrestrained. Four of the paintings were on copper, and one was painted on tin-plated iron. Various condition issues, all common with paintings on metal, were present; the most serious issues were corrosion (which consisted of brown stains and corrosion products protruding from the paint layer), distortion of the support, flaking paint, discolored varnish, and puncture holes where the paintings had been nailed to walls or altars. In addition, large areas of overpaint were present.
Treatment of the paintings began with documentation and an initial analysis of the imagery depicted. All of them appeared to be allegorical or religious, and a few were clearly similar in composition and subject to other, more famous paintings, such as the painting referred to as “Disciples of Emmaus” by the center, which featured two parrots that were exact matches to those in a Jan Breughel painting from c. 1620.
Cross sections of the paintings were taken in order to help conservators to distinguish between original and later paint. The four paintings on copper were found to have a lead white ground, and the painting on tin-plated iron had a ground consisting of Prussian blue and lead white. Varnishes were found to be mastic or dammar, but were clearly not original for several of the paintings. UV examination revealed aggressive cleaning and intervention in the past.
In order to determine the best methods for treatment, copper prototypes were created and used to test adhesion of various adhesives. The CNCR used Isabel Horovitz’s research into paintings on copper as the primary resource for their work. Following testing on the prototypes, corrosion was mechanically removed, and a solution of 15% B-72 in toluene was used to isolate the corroded areas and to consolidate flaking paint.
Distortions in the support were significant on a few of the paintings, and conservators hoped to be able to reduce it. Flattening was attempted on prototypes using a book press, and the result was considered to be less distracting. A few of the paintings were flattened in this manner. An acrylic plate was applied to the reverse to provide support and to allow the reverse of the metal plates to be seen.
15% B-72 in toluene was used as a base for filling losses in the paint surface, and a tacking iron was used to level the edges of the fills. Fills were isolated with a varnish and inpainted to a full visual reintegration. After cleaning and inpainting, the subjects of the paintings were revealed to be religious and not allegorical. The center has suggested re-naming the paintings accordingly, and has sent their proposed titles to the O’Higgins museum. The treatments and the revealed subjects will be summarized in an upcoming book.
42nd Annual Meeting- Book and Paper Session, May 29, 2014, "Preserving the African American Scrapbook Collection of Emory University Libraries by Ann Frellsen, Kim Norman, Brian Methot"
This three-year Save America’s Treasures project was presented in a three person tag-team. The project represented a collaboration between the Emory University Libraries Preservation Office, Digital Curation Center, and Manuscript, Archives, and Rare Book Library (MARBL). Emory University Libraries Conservator Ann Frellsen began the presentation with a project overview. The large scale of the project, combined with the diverse materials in the scrapbooks, required rigorous assessment and planning to fit the project schedule. The forty scrapbooks were narrowed to a group of 34 high-priority items. Then the scrapbooks were assigned to three treatment “levels,” roughly approximating the categories used in ARL (Association for Research Libraries) statistics, based on time and degree of difficulty. The past preservation approach for the collection had been to simply limit patron access by “boxing and forgetting.” For this collection of African American scrapbooks, the library intended to expand access through digitization.
The initial project proposal would have relied on a conservation technician, but the complex construction and fragile materials required a conservator’s skills. The project plan was adjusted, and the second presenter, Kim Norman, became the project conservator. The initial decision tree was quickly abandoned as the diverse scrapbooks were assigned unique treatment plans, corresponding to the specific preservation problems presented by each item. Common problems included folded items, detached components, and overlapping elements. Adhesive stains were generally left in place, where they provided useful evidence in positioning detached items.
In some instances, new support pages were created, but many of the album pages could be encapsulated or placed into unsealed Melinex sleeves to provide support at the page level.
The third presenter, Brian Methot, described the workflow for digitization. The reflectivity of the Melinex was a hindrance to photography, so the sequence of operations was adjusted to provide for encapsulation after digitization. Ehtafoam and binders’ board shims augmented cradles used during scanning. Custom-built platforms supported delicate fold-outs during photography. There was a vacuum table as a part of the photo studio, but the thickness of the materials made the vacuum ineffective. Instead, the photography used a sheet of Acrylite acrylic. Blank pages were also scanned to maintain the correct order and appearance of the pages.
Brian also described technical requirements for the project. The library needed a camera with a faster scanning back to capture details of these large and complex pages. Cool LED lights replaced hot tungsten studio lights as well. The Phase1 camera with Mamiya scanning back was tethered to a an Apple computer running Capture1 software, which handles both image processing and metadata. The process generated three file types: MOS native camera format files, Archival Master files (TIFF at 400 ppi with color target and ruler), and Production Master files (TIFF at 400 ppi, cropped to image).
The presenters further clarified the project details during the question and answer session. A major objective of the project was to make restricted items more accessible to the public. It is hoped that additional metadata can be crowdsourced through the open online repository with the digitized scrapbooks. There will be a digital-first access policy, so researchers will have to request special access to the originals. Regarding the conservation treatment, the paper was not deacidified prior to encapsulation. Pages were not necessarily sealed on all four edges, so this should not be a problem.
The project was successful in providing structural stabilization for the original copies, while also enhancing access to the scrapbooks’ contents. The project was discussed in Kim Norman’s blog and in the New York Times, increasing public awareness of the collection. The project has also begun to yield broader results by connecting community members with collection items.
42nd Annual Meeting – Collection Care Session , May 29 “Conservation Assessment at Schloss Leopoldskron in Salzburg, Austria: Promoting Sustainable Choices for the Adaptive Re-use of the Collection and the Site” presented by Rita Berg, Graduate Intern in Paintings Conservation, Brooklyn Museum and Crista Pack, Kress Fellow, Arizona State Museum.
Beautiful landscapes to boot, this talk illustrated how graduate students gained experience in preventive conservation by identifying the collections care needs of a prominent historic site that is also a busy event space/hotel.
In the summer of 2013, four students from New York University and the Winterthur/University of Delaware Program in Art Conservation — Rita Berg and Cybele Tom (NYU) and Crista Pack and Emily Schuetz Stryker (WUDPAC)—performed a conservation assessment of the historic collection at the Schloss Leopoldskron, under the supervision of Hannelore Roemich, Professor of Conservation Science at NYU and Joelle Wickens, Associate Conservator and Preventive Team Head at Winterthur. The talk was dedicated to Emily who passed away unexpectedly in February of this year.
Crista and Rita presented by discussing the building’s history, the goals of the project, the group’s workflow and theoretical approach, recommendations for the future, and lessons learned. The Rococo palace was commissioned by Count Leopold Anton Eleutherius von Firmian, and was once owned by Max Reinhardt. It is now an Austrian national historic site, and host of the Salzburg Global Seminar (SGS). The assessment project was co-sponsored by the Kress Foundation and SGS.
The Schloss is not only a magnificent edifice—it is familiar to many as the inspiration for the Von Trapp villa in The Sound of Music—but its historic collection includes paintings, works of art on paper, furniture, decorative arts and sculpture. Unfortunately the collection’s condition has never been systematically documented.
The major goals for the project included developing a long-term strategy for caring for the collection, as well as providing educational training for students who were able to test theoretical approaches in a “real-world” scenario (though it was admittedly hard to think of the bucolic, dream-like setting of this palace as “real-world”). However, major challenges quickly presented themselves to the students: food and beverages could be found throughout the house, candles were lit regularly, there were many open windows, objects vulnerable to theft, chaotic transportation and storage of objects during events, wildlife, dust and dirt accumulation.
The group worked in pairs to assess rooms, and three different types of object groups (prints, paintings and architectural elements) using photography and written survey forms that they had developed. They interviewed staff and local scholars, recorded patterns of use and consulted existing literature from the National Parks Service and the Conservation Assessment Program.
Among their recommendations were that the SGS articulate the presentation of the building and collection directly in its mission statement, appoint a collections manager, establish guidelines for events and handling. They also identified that the paintings, which were among the most valuable objects, are at the highest risk.
Although they found inherent contradictions in the house’s dual function as a historic site and event space/hotel, the students aimed to raise awareness among staff, owners and guests of the collection’s needs. This was done they maintained, keeping in mind the priority of the space’s functionality. This July a new team of conservation students will continue the project following the guidelines established by their predecessors. And judging from the Alpine landscape, lucky them.
42nd Annual Meeting – RATS Joint with Objects Session, May 30, “Technical Study and Conservation of the ‘Bat Wing Ship,’ Background, Challenges and Surprising Discoveries, Lauren Anne Horelick , Objects Conservator, Smithsonian National Air and Space Museum
The compelling object at the center of this paper is an experimental prototype of a Nazi German jet powered fighter aircraft discovered by the Allies at the end of World War II and brought to the United States for study. Designed by the Horten Brothers (Reimar and Walter), this craft with a steel structure, paper-thin plywood veneers, and no vertical tail is regarded as a design predecessor to the stealth bomber. The aircraft, a model Horten Ho 229 v3 (the third and final version of this particular airframe) was captured when it was near completion in the Gotha workshop http://airandspace.si.edu/collections/artifact.cfm?object=nasm_A19600324000 Charcoal was said to have been added to the construction adhesives to make the aircraft invisible to radar.
While always a favorite of air flight/military history buffs, this craft has never been exhibited and has been the subject of increased interest in recent years due to what the paper’s author describes as a “sensationalized” documentary entitiled “Hitler’s Stealth Fighter.” This video, available on YouTube, is replete with inaccuracies including the assertion that it is stored in a “secret government warehouse” when, in fact, its current home is the Smithsonian’s Paul E Garber Facility in Suitland, Maryland. However, it will soon be moved to another disclosed location – The Udvar-Hazy Center in Chantilly, Virginia where it will have its big reveal.
In preparation for this move, conservators at the Smithsonian NASM carried out a technical study to inform treatment protocol for the stabilization of the unstable and extensively delaminating veneers. They sought to characterize and identify the adhesives and other materials employed and, in particular, seek evidence for the presence (or apparent lack) of charcoal.
The aircraft is 55.4 feet wide with a tubular steel frame. The engine rests in the center of the craft and it is covered in a plywood skin. There is a clear canopy for the pilot. Due to complications of working on the object in its storage location, the decision was made to disassemble the damaged plywood portions to allow for treatment of the panels in the conservation lab. The composite materials that were examined and analyzed included the plywood board, structural supports and spacer blocks including the adhesives used to attach these portions to one another.
After a literature review of plywood available in Germany before WWII, reference materials were acquired for the potential materials. A sampling protocol was developed and the object and reference samples were examined under visual and Polarized Light Microscopy, FTIR, Raman, and for selected samples XRD was employed. (There may have been other methods employed that I missed in my notes– GC-MS and 3-D microscopy were mentioned in the abstract – sorry if I have omitted something significant.) The analysis was done in conjunction with the Museum Conservation Institute.
The analyses yielded some unexpected results as some of the wood sample results varied from those specified by the Horten Brothers (as reported in their interrogation). However the substitutions of European Beechwood/Scots Pine for the specified birch was not very surprising to the authors given the materials shortages at the end of WWII. The adhesives tested were identified as urea formaldehyde and phenol formaldehyde. Confirming the presence of charcoal in the black paint/adhesive layers proved elusive. The black particles were difficult to separate from the matrix. PLM examination did not support the charcoal identification and they were found to be amorphous with XRD. FTIR analysis pointed to the presence of cellulose, hemi cellulose and phenolics. This could mean oxidized or charred wood – or neither.
Plans for treatment do not include repainting damaged areas as the author mentioned a growing trend toward exhibition of aircraft in a less heavily restored state. Beech veneers will be employed in areas of loss but were unavailable in the United States in the <1mm thickness required so must be ordered from Germany. Because the urea formaldehyde has cross-linked with age and become insoluble, the conservators are not as concerned as they might have been about adding new materials when they choose an adhesive to stabilize the veneers.
Details and updates on this research project and the treatment are available on the on the National Air and Space Museum’s Airspace blog http://blog.nasm.si.edu/restoration/horten-h-ix-v3-bat-wing-ship-may-2014-update/ The Bat Wing Ship is poised to be a popular attraction when it goes on exhibit – I know my interest has been piqued by this interesting talk!