Specialty Sessions – Page 47 – AIC Blog Archives: Conservators Converse

39th Annual Meeting – Architecture Session, June 3, “Assessment and Characterization of the Architectural Metal Finishes at Fort Moultrie: A Successful Student-Scientist Collaboration” by Stéphanie A. Cretté, Lisa M. Nasanen and Néstor G. González-Pereyra, Clemson Conservation Center, Warren Lasch Laboratory; and Frances H. Ford, Clemson University/College of Charleston Graduate Program in Historic Preservation

Amelia Millar from the Clemson University/College of Charleston Program in Historic Preservation, and Stéphanie A. Cretté from the Clemson Conservation Center presented a two-part paper on a graduate-level project at Fort Moultrie National Monument near Charleston, SC. Millar presented the student portion of the work, while Cretté presented the analytical research.

The project entailed a survey of metals in a portion of the Fort Moultrie site, owned by the National Park Service. Students from the Clemson University/College of Charleston program performed a survey of all existing metals, both architectural metals and the metal objects on site, and assessed the condition of the metals. They took paint samples to determine the chemical composition of the paint so that NPS can develop a strategy to safely remove any lead-containing paint while preserving the metal substrates. The students did most of the field work and tested paint-removal methods, then collaborated with scientists from the Clemson Conservation Center on SEM-EDS and Raman analysis of the paints. Most of the scientific portion of the presentation was about the analytical techniques and why they were used for this application.

The paper was interesting, but I would have liked to have learned more about the researchers’ findings and the various treatment recommendations put forward by the students. It would have also been interesting to learn whether the NPS has implemented or plans to implement any of the student recommendations. Nevertheless, it was a good collaborative project that seems to have benefited the students and scientists alike.

39th Annual Meeting – Paintings Session, Katlan Palettes of the Salamagundi Club, Cox The longterm relationship

I was incredibly lucky with the two talks that I chose to blog about. I had tried to find some talks that were not too technical as I felt that I would not have too much to comment upon if I did not understand the science of the talk. I was drawn to the topic of the Salamagundi club because I grew up around the corner from the present day Salamagundi club in New York City. Further I was interested in Ruth Cox’s talk about fostering a long-term relationship between private conservator and a museum collection, as I am a private conservator. But enough about me and on to the talks.
In his talk about the Salamagundi Club palette collection Alex Kaltan briefly described the history of the painters palette. He discussed the rarity of palette collections and described both the Salamagundi palette collection and the Grumbacher paint company palette collection. Katlan stressed the importance of artist materials in collections and the fact that they have been overlooked in the past but that they can be invaluable additions to study collections and provide insight into the working practices of artists. The Salamagundi club collection itself is made up of both working palettes and demonstration palettes. A working palette is an actual palette that the artist worked with over a period of time and differs from a demonstration palette, which is an unused palette with the artist paint colors in the manner in which they did when painting. Katlan describes the great variation in the arrangement of color on the palette and how this arrangement gives a lot of information about the thought process of the artist.
What struck me about Katlan’s talk is how well it tied in with an earlier talk in the PSG session by Narayan Khandedkar about the working habits and palette of Delacroix. Also I was touched by how these objects are a personal link to the artist workings methods.
The second talk by Ruth Baruch Cox outlined her long-term relationship with the Reynoldo House Museum. Cox explains that she functions as more than a treatment conservator at this institution where she has done 2 conservation surveys and created a disaster plan in addition to performing several conservation treatments.
The rest of the talk focused on the treatment of Spring Turning by Grant Wood. The treatment was complicated by Woods varnishing practices and former treatments. The museum has produced a video about the treatment and a brochure on the care of paintings.
I was disappointed that there was not more about the long-term relationship between the conservator and the museum. It seems that the talk about the treatment of the Grant wood is a separate topic from the long-term relationship with the museum. However that is just my personal view as I am a conservator in private practice and I also try to foster meaningful long-term relationships with my museum clients.
Overall I was very impressed with the quality of these two talks.

39th Annual Meeting – Objects Session, June 1st, “Archaeologists and Avocational Conservators: Compromising Principles or Increasing Awareness?” by Susanne Grieve

This year, a portion of the OSG sessions focused on archaeological conservation and the ethics and issues surrounding the conservation of these materials. The paper presented by Susanne Grieve focused on avocational conservators and how much information do we give to non-conservators who are practicing conservation, something that was touched upon in the panel discussion organized by the Archaeological Discussion Group of the OSG on ethical issues in archaeological field conversation held earlier that day.

Avocational conservators were described as members of the general public who undertake conservation treatments as a hobby or out of interest for preserving something. They have no formal training in conservation. In her presentation, Susanne talked about working with a group of avocational conservators in Namibia who help preserve maritime sites and artifacts in the country. The group is made up of members of the the Windhoek Underwater Club’s (WUC) Maritime Archaeology Division who come from varied background with no formal training in archaeology or conservation.

Susanne brought up some interesting questions and issues as she talked about her experiences working with the WUC. Conservators have worked for 39 years to make conservation a profession. We have formalized training, a code of ethics and protocols and standards that form the basis of the profession. Her questions in regards to the conservation profession and avocational conservators is: Do we work with these groups? How much training do we give them? And do we compromise our profession by working with or training these people?

In regards to the situation in Namibia, there is only 1 conservator responsible for all the cultural material there. This means that there is not enough staff and resources to get everything done. The avocational conservators do the work they do because it is very important to them that this part of Nambian culture and history be preserved and they have an interest and passion in doing so. And I’m sure they feel that because of the limited resources there, they can help fill that need.

Susanne’s work with the WUC involved working with them on the excavation of a mining camp site and the conservation of material found there. The club felt the site was important for them to preserve because the government was not interested in preserving it. The camp site was from a German mining operation and places like these are not preserved because it is a part of Namibia’s past people want to forget. Susanne worked on site with them and taught them about excavation and lifting techniques. They then took artifacts back to the lab where she taught them some basic methods for preserving books and ledgers collected from the site. She also looked at some previously treated artifacts that had been conserved using outdated methods and shared information on other approaches. Before leaving she left some conservation materials with the group.

Susanne’s paper touched upon issues that many conservators deal with when having to work with non-conservators in resource poor institutions. These kinds of questions often come up in working with archaeologists as well. In the case of the conservation of maritime sites and artifacts in Namibia, it seems that the WUC are the only group at the moment who can preserve this material. The infrastructure and resources don’t seem to exist to allow for conservation professionals to do this kind of work. There is too much to preserve and not enough trained people to do it. So does that mean that we, as conservators, don’t do anything because working with avocational conservators would compromise our profession? It doesn’t seem like these questions could be easily answered, but this talk does bring up important questions that as a profession should be discussed because many of us have to deal with issues such as these.

Susanne summed up her talk with what I think is a good approach to these questions and something as an archaeological conservator, I agree with. She felt that the answer to the questions she posed should be considered on a case by case basis. If the person you may be working with is interested in selling artifacts, then you shouldn’t share your knowledge. However if the purpose is to educate people, especially in countries with no resources or professionals, then perhaps we should share our knowledge and skills. In regards to working with archaeologists, it is important for them to see archaeological conservation as a profession. They need to value the knowledge and skills we can contribute. Susanne’s suggestion is to continue to work with archaeologists so that this type of thinking starts to change. And I couldn’t agree more with this idea.

39th Annual Meeting – Architecture Session, June 3, “Comparative Study of Commercially Available Rust Converters” by Jason Church, Anna Muto and Mary F. Striegel, National Center for Preservation Technology and Training

Jason Church from NCPTT presented a useful paper on commercially available rust converters. He explained that rust converters are a chemical treatment that converts iron oxide into a more stable product, though this product varies depending on the chemical composition of the rust converter. Church and his colleagues started with the 1995 Canadian Conservation Institute study of rust converters, but found most of the products to have been discontinued or available in new formulations. This led the team to perform their own experiment.

Church et al., selected four commercial products of varying chemical composition: Ospho (phosphoric acid base), Rust-oleum Rust Reformer (tannic acid base), Corroseal (gallic acid base) and RCx427 (oxalic acid base). The four commercial products were selected on the grounds that these products were readily available, were top sellers, and could be purchased in sufficiently small quantities so as to be accessible to homeowners or for small conservation projects. Church and his colleagues also tested the CCI-recommended custom formulation of tannic and phosphoric acid, which several objects conservators they polled still claim to use. NCPTT staff tested the five rust converters on new A36 carbon steel that was naturally weathered. They subjected each of the test samples to artificial weathering and measured the samples for color changes and active corrosion every 250 hours for 1000 hours total. They found that the Rust-oleum product had the least color change and most stable surface of the five products tested, though the efficacy of each product tested was quite varied. Church mentioned that their testing is not complete. They continue to push the Rust-oleum product to metal failure through extended artificial weathering, and will also test the new aerosol version of that product. They also plan to perform outdoor accelerated weathering tests on the five products.

The presentation was interesting and informative, as is characteristic of studies done by NCPTT. I like that their experiments are developed for conservators, but the results are accessible to anyone. The information presented in this talk will surely broaden the body of knowledge for architecture and objects conservators and will be useful for homeowners and maintenance workers. Following the talk, moderator Patty Miller recommended that they eventually expand their testing scope to include conservation-grade products and less readily available materials. I concur, and I would encourage Church and his colleagues to publish their findings.

39th Annual Meeting – Book and Paper Session, June 3rd “Nicolas De Fer’s L’Amerique Wall Map: A Look into the Ethical Dilemmas Resulting from Past Restorations”

Doris St-Jacques and Maria Bedynski of Library and Archives Canada presented the challenges they faced when working on the restoration of a hand colored 1739 ed. L’Amerique Divisee selon Letendue de ses Principales Parties wall map.

Highlights of the talk included images of anthropomorphized, bipedal, dam building beavers (Follow the link for more information on the map itself, and especially the beavers!) and the description of the Library and Archives Canada’s “light wall”. I don’t think I was the only attendee green with equipment envy at the thought! I know next time I get to design a new lab space, I will be investing in frosted glass and fluorescent light fixtures.

Library and Archives Canada has two copies of L’Amerique, a map that is important not only for the textual information and hand colored map, but also for the various illustrations of daily life in the Americas. Their 1689 ed. is in relatively good condition except for heavy trimming, but the 1739 ed. had been brought to conservation in poor shape. The 1739 ed. had had been previously, and creatively, restored.

The map had originally been printed on several panels that were glued together in overlapping segments. The left text panels had been cut from the map during the previous restoration. As a result, there were definitive breaks between panels that were tenting up and fragmenting at the edges.
The map had been lined with acidic machine pulp paper (date unknown).
The map had been trimmed and been given a decorative machine marbled paper border (date unknown).
The text panels were extensively damaged, and had been in-filled in a variety of creative and baffling ways.
- Some segments were infilled with replacement printed text. This text was not only not from the same map, but was not even in the same language.
- Some segments were decoratively infilled with meaningless scribbles, no doubt meant to emulate text.
Small fragments from the text had been retained, but had been re-adhereed to the map in seemingly random places.
The two bottom text panels had been reversed.
An opaque grey paint had been used to mask areas of loss/damage – further obscuring full lines of text in some areas.

The conservators approached the complex dilemma of L’Amerique by consulting the 1698 ed. of the map which also resided in their collection. Unfortunately, a previous treatment to that map had heavily trimmed the edges, resulting in significant text loss that made the map unsuitable as a guide. The conservators were able to purchase a facsimile copy of the map, printed at 1:1 aspect ratio, from the University of Michigan @ Ann Arbor. Notes on the full treatment of the map are as follows:

The Reboot:

The full map was humidified, the marbled paper border removed, and the map separated into individual panels. Humidification allowed the panels to be delaminated where they overlapped, so that the margins were retained where still present.
Each text panel was pre-treated with alcohol, then immersed in a water bath to remove the paper lining and heavy adhesive layer.
The two hand-colored map panels could not be immersed in water due to their soluable colorants, so instead, the adhesive and lining paper were removed by laponite poultice. They were then cleaned by spray misting and light sponging through pasting tissue.
Gelatin was brushed through pasting tissue to resize the paper of all the panels
The “creative” infills were carefully removed.

The Repair:

Leaf casting and hand pulp infills were used to restore areas of loss in each map segment (and to replace the severed margins on the left text panel), and each segment was lined with thin Japanese tissue and allowed to dry.
The individual sections were then reassembled into the 4 original panels (map, left text, right text, bottom text). It is at this stage that the conservators were able to switch the left and right sections of the bottom text panel back into their original configuration.

The Reinforcement:

Terylene fabric was spray-wetted then pasted out with wheat starch adhesive and adhered to the lab’s light wall. Sheets of kizukishi paper were water torn at the edges and pasted out. They were adhered to the terelyene to form one large sheet of lining tissue. The tissue/fabric laminate was then allowed to partially dry to reduce the likelihood that the lining tissue would be disturbed/damaged during the map mounting phase.
The laminate was repasted out and the map sections (1st the map, then the text panels) were humidified and rolled out onto the kizukishi tissue. Since the conservators were working on the drool worthy light wall, they were able to easily reach different parts of the map for exact repositioning.
It was decided to retain the marbled paper because it obscured nothing, would be easy to remove if necessary, and was a part of the history of the piece. The border was readhered to the map in the original configuration.
The map was allowed to dry on the light wall.
Once dried, the map was carefully peeled free from the light wall, with the terelyne serving as a release layer. The map was placed face down, and the terelyne carefully peeled free from the tissue lining.
A second layer of water torn tissue was pasted onto the map as a final layer of strength.

The Record:

From the start, the conservators were concerned about dimensional change during the humidification and lining of the map. To guard against misaligned fragments, the map was extensively measured and photo-documented before treatment began.
As the various creative infills were removed, they were adhered to a mylar overlay in their home positions.
During the treatment, it was realized that the title banner was delaminating. Viewed with tramsitted light, it became obvious that the L’AMERIQUE title banner had been pasted over a printed EUROPE banner, and in fact some of the original letters of the EUROPE banner had been altered as a part of L’AMERIQUE. The conservators found a that this was also the case on their 1698 ed. map, and that digital images of the same map at other institutions showed a delaminating title banner as well. So the conservation treatment of this map actually revealed a new fact about the printing methodology used by the map’s creator, Nicolas De Fer.
A full and complete version of the map text was printed onto a second mylar overlay to be stored with the original map.
Fragments of the acidic paper lining were retained to save the impression of the original cloth lining still present in the thick adhesive.

39th Annual Meeting – Objects Morning Session, June 2, “Establishing a Code of Ethics in Korea: Challenges and Dilemmas” by Dr. Sujeong Lee

Dr. Sujeong Lee with the National Research Institute of Cultural Heritage in Korea spoke regarding the current efforts being made towards establishing a Code of Ethics for the Korean government and conservators. She comes from a background of studying the history and theory of conservation with a particular interest in value assessment. She presented her paper as answering two primary questions: 1. Why does a Code of Ethics need to be established in Korea/Asia? and 2. What is the process for establishing a Code? From the start, she established that she was at the conference as a representative of the Korean government and that she was meant to present the country in a positive light but that she was here to ask for help and advice and not to mask the difficulties her country is facing in their quest to establish ethics.

In answering the ‘why,’ Dr. Lee provided a history of the past one hundred years of conservation in Korea, a field which has evolved largely in response to the damages of occupations and war. The Japanese occupied Korea up until WWII and from 1950-1953 the country experienced the Korean War, referenced as the “three year war” by Dr. Lee. In the wake of these events, Korea has spent the last sixty years attempting to repair the many buildings and objects that were damaged, a process that she contends resulted in the loss of many of the fundamental ideas of conservation. It is now her goal to help the country regain an understanding of why conservation should be undertaken, the methodology for doing so, and the best materials to use. In order to underscore the loss of real ethics in Korea, Dr. Lee explained the legality of being a qualified conservator in Korea and the certification process that each undergoes. During the testing and interviews, each individual is assessed based on their ethical qualifications; however, there are no standards for doing so and even after becoming a certified conservator, Dr. Lee finds that many individuals are unequipped to address the many decisions they must make as a conservator. She feels that developing a Code of Ethics would help in the training of conservators as well as give individuals a standardized and approved manner for approaching conservation. Significantly, there is has also been a recent growth in public awareness and participation in the stewardship of high-profile objects and buildings in Korea. In support of this trend, Dr. Lee presented the case of the 2008 arson of the Namdaemun gate, a 14^th c. treasure located in the center of Seoul. Following the tragic destruction, the public responded by laying flowers in front of the building and generated enough emotional investment that the conservation efforts were reported on a continuous basis.

The recent increase in the number of conservators registered in Korea is another determining factor contributing to the present need for a Code. There are currently approximately two thousand conservators registered, though Dr. Lee is concerned that many of them are unfamiliar with the principles, techniques, and practices of conservation, something she feels that a code will assist in remedying. Perhaps the most compelling reason she presented for why Korea must establish a Code is that it will be the first Asian country to do so, and thus hopefully not the last.

The second question, the ‘how,’ is unsurprisingly a more complicated topic and one that has yet to be fully realized in practice. The committee charged with developing the Code has examined many of the other codes currently in use, including that of the AIC. At the start of the process, Korea held an international conference in order to understand the many issues they were grappling with. Dr. Lee reported that the conference was widely attended, which was both surprising and encouraging for their efforts. They have hosted a series of conferences; the first discussed the benefits of developing a Code, the second focused on listening, and the upcoming seminar will attempt to separate the junior and senior associates so as to achieve a more comprehensive and honest analysis of the field and the ethical concerns. Dr. Lee is optimistic about the future of the code but admits that there is still much to be done. She concluded her presentation by once again requesting that anyone with advice contact her as she and the others behind the development project are very eager for input.

See also: http://www.conservation-us.org/index.cfm?fuseaction=page.viewPage&PageID=858&E:\ColdFusion9\verity\Data\dummy.txt

AIC’s 39th Annual Meeting – Paintings Morning Session on June 3, “Industrial Literature as a Resource in Modern Materials Conservation” by Dawn V. Rogala

Artists working in the post-WWI era frequently used industrial products in their work. This can put conservators in the position of dealing with materials with unknown compositions and behaviors that are not conducive to long-term preservation. Unfortunately, existing conservation literature does not always provide adequate materials information or case studies for conservators wrestling with these issues. Expanding literature searches to include period industrial articles can fill in those informational gaps.

Dawn Rogala discovered the benefits of such industrial literature while researching mid-century American oil-based zinc oxide house paint during her postgraduate fellowship at the Smithsonian Institution in Washington, DC. Her research focused on a group of abstract expressionist paintings and the relationship between their zinc oxide grounds and failure of the paint layers. She found that industrial literature provided significant evidence of a connection between the choice of materials and the current unstable condition of the paintings.

The period between 1925 to 1950 provided Rogala with the most useful articles, likely due to market demand and frequent product adaptation during that time. The largest percentage of articles she found were presented by representatives of the paint manufacturers who were focused on promoting the benefits of their paint to consumers. Those may seem like biased and unreliable sources for accurate information, however such articles often mentioned engineered mechanical behaviors that were considered beneficial in their paint films. Approximately 25% of the articles in her research were affiliated with scholarly research. Those articles provided more comprehensive and practical analyses of paint film behaviors with useful reference bibliographies.

Weathering test articles were another rich source of information on paint formulations and behaviors. The variations in regional weather often caused adaptations in regional paint formulations. This meant that artists working with a zinc oxide house paint in a mild climate may have worked with an entirely different formulation of zinc oxide house paint than an artist working in a more severe climate during the same period. It also suggested titanium dioxide’s introduction into house paints in the mid-1950s could have been delayed on a global scale when considering issues of climate influences on formulation changes.

One of the specific examples Rogala gave to illustrate the usefulness of industrial literature referred to self-renewing paint films. Weathering test articles cited a preference for acicular particles because their brittle nature allowed for microfissures in the paint, which would cause it to slough off in the rain and result in a crisp clean surface. Another example was the mention that three years was the required life expectancy for engineered paint films according to industrial standards. While such qualities were acceptable and even desirable in house paints, such paint films pose clear disadvantages for conservation. In fact, Rogala pointed out a 1909 article that warned about the dangers of zinc oxide paint as a ground layer!

I thought this was an outstanding presentation. Conservators must be resourceful and adaptable when dealing with unknown, unpredictable materials. This is a particular necessity when it comes to the conservation and preservation of modern and contemporary artwork. I appreciate Rogala’s study for delving into the industrial side of zinc oxide and providing an open look at a somewhat unconventional resource for conservation research.

AIC’s 39th Annual Meeting – Paintings Morning Session on June 3, “The Construction and Reconstruction of the 15th Century Spanish Retable” by Judy Dion

Judy Dion’s study of 15th-century Spanish retables adds to the limited information available on the impressive altarpieces that have undergone less technical and historical research than their Northern European and Italian Renaissance cousins. Dion’s research is the result of five years of collaborative efforts during her Mellon Fellowships at the Balboa Art Conservation Center and the Philadelphia Museum of Art. The study involved extensive non-invasive examination of panel paintings from the collections at the San Diego Museum of Art and Philadelphia Museum of Art, as well as paintings in Spain, the United States, the United Kingdom, and mainland Europe. Dion focused her investigation by concentrating on panel paintings made in the Spanish regions of València, Catalonia, and Aragón. Her findings address construction methods specific to Spanish retables, how construction features on individual or smaller sections of panels can provide clues to their placement within a complete retable, and the history and changing attitudes regarding alterations of disassembled panels.

To summarize the discussion of construction, retables consisted of a central panel surrounded by additional panels usually in the form of an inverted T-shape that measured anywhere from two to seven meters high. The panels were in a fixed position and surrounded by framing components that served as pictorial and transitional elements between the scenes. Review of the fabrication methods showed the panels, most often constructed from poplar or pine, were assembled using butt-joined boards with battens. Transverse battens were used in combination with either vertical or diagonal battens but the latter were never used together. All of the retables from the Valencia region examined in Dion’s study had diagonal battens and metal dowels were common additions. Any flaw in the panels were filled with wooden shims and gesso before painting commenced. Nonwoven plant fibers and fabric were also used in preparation of the panels.

In my opinion the most interesting part of the construction was during the assembly step that included the framing elements. The frame components were attached to one of any two adjacent panels and then overlapped the face of the second panel. Raised framing elements were installed during the final assembly. This construction caused a bare edge and gesso burr on the side of the panel with the attached framing element, while the paint layer extended to the edge of the side that was overalapped. As a result, individual panels often appeared asymmetrical when retables were disassembled.

The disassembly of retables was often a response to changing aesthetics, demand for profit, and damages. Individual or smaller panel sections could hold a higher value than an intact retable. This led to frequent alterations of the panels to improve their appearance as stand-alone works. Such alterations included but were not limited to repainting, the addition of false elements, and cutting down of the panel edges. Fortunately, shifts in the methodology of collecting institutions encourage the recognition and appreciation of the historical context of fragmented works. Panels that were altered for the aforementioned reasons are increasingly the subjects of reversal treatments. In some cases the alterations are left visible, while in others missing or altered elements are restored to recover evidence of their original appearance.

This is a very abridged overview of Judy Dion’s thorough research and presentation due to my mere mortal status as a note taker. I encourage anyone interested in this subject to seek out the conference postprints and/or approach Ms. Dion with any questions regarding her study. She applied her findings to a hypothetical reconstruction of Jaume mateu’s The Birth of the Virgin, from the John G. Johnson Collection at the Philadelphia Museum of Art. It is an excellent case study and definitely worth a review to gain a greater understanding of this research.

39th Annual Meeting – Book and Paper Session, Wednesday, June 1, “Practical Applications of Lascaux Acrylic Dispersions in Paper Conservation,” Samantha Sheesley, Conservation Center for Art and Historic Artifacts

Due to their stability, reversibility, and working properties, Lascaux 360HV and 498HV adhesives are becoming increasingly popular in book and paper conservation. Samantha Sheesley of the Conservation Center for Art and Historic Artifacts presented three case studies of treatment applications that take advantage these properties.

The first case study involved treatment of a set of “Sailor Jerry” drawings on transparent paper. Both the presence of water-sensitive media and the reactive nature of the transparent paper meant that Sheesley was looking for a way to mend the drawings without introducing moisture. Lascaux 498HV was brushed in an even film layer onto a sheet of silicone-coated polyester and then quickly dried with a hair drier. Sheesley pointed out that this quick drying is an important step in order to prevent dust from settling into still-tacky adhesive. After drying, a sheet of tengucho mending tissue was placed on top of the 498HV film layer; the adhesive was reactivated with an iron to adhere the paper to the film. After removing the silicone-coated polyester, the adhesive-coated tengucho was used to create mending strips that were applied to the drawings with heat, resulting in nearly-invisible mends that are easily reversed with either heat or solvent (acetone or toluene).

The second treatment example of was the re-lining of a lithographic poster. A hydrophobic coating on the paper and water-sensitive media required a dry lining method. Lascaux 498HV was applied to a sheet of silicone-coated polyester (a light mist of water under the polyester secured it to the bench) and squeegeed in multiple directions to create a thin, even film – Sheesley emphasized again that it was important to work quickly when applying and drying the film layer in order to avoid dust settling in the adhesive. Lining paper was placed on top of the dry adhesive film and adhered with an iron. Once cooled, the silicone-coated polyester was pulled away from the lining paper. The poster was placed face down on a suction table to keep all pieces in place and then the lining paper was dropped adhesive side down, tacked in place with an iron, removed from suction table and ironed overall.

The third case study – in my opinion, the most ingenious of the applications – involved the use of a Lascaux mixture as a fill material for a convex photo button with a severe horizontal split. The button was a silver gelatin print with a cellulose nitrate coating on a metal substrate. The tented split created a gap that was both structurally and aesthetically problematic. Sheesley needed a fill material that would be flexible enough to accommodate dimensional changes in the object. She mixed equal parts Lascaux 360HV and 498HV, in order to take advantage of the unique properties of each, and added pigment. As in the first two examples, this mixture was brushed onto silicone-coated polyester and quickly dried. She scored the edge of the pigmented film and removed a small strip which she then rolled into a coil – the inclusion of Lascaux 360HV in the mixture, which retains it’s tackiness even when dry, meant that there was just enough residual tackiness for the adhesive film to stick to itself. After mending the photo with small strips of Beva (which were inserted in to the crack with very fine-point tweezers) the Lascaux coil was fitted into the gap and tacked in place with an iron. Sheesley then ironed the coil overall through a sheet of silicone film which imparted a shiny texture to the surface of the Lascaux fill, mimicking the surface quality of the cellulose nitrate for better visual integration. The fill was then inpainted with acrylics. The “after treatment” photos of the button were impressive – I hope an appropriate object comes across my bench soon so that I can try out this technique!

Q: Does creating repair tissue using dry adhesive rather than wet adhesive (i.e., brushing diluted Lascaux onto mending tissue) create a less transparent mend?
A: Sheesley tested both methods and found then to be similarly transparent. She also speculated that the the dry film methods would be more easily reversible, since the adhesive doesn’t penetrate into the mending paper fibers as it would in a wet application.

Q: Were any adverse effects of using the hot iron next to the cellulose nitrate?
A: No harmful effects were observed.

Q: Was there any residual tackiness on the coil infill, since it contained 360HV?
A: No, the presence of 498HV in the mixture and the acrylic paints on top of the fill meant that there was no remaining tackiness.

Q: Concerns about reversibility.
A: Sheesley stated that though reversing the treatments could be time consuming, she was able to reverse all of her repairs.

39th Annual Meeting – Paintings Morning Session, Friday June 3 – “An Experimental Study on the Merits of ‘Virtual Cleaning’ of Paintings” by John Delaney

John Delaney discussed the “yellow filter” model for virtual cleaning and compared it to experimental results from measurements of cleaned paintings before and after treatment. To estimate the result of removing a discolored varnish, conservators sometimes correct the color using imaging software, “subtracting” out the varnish as if it were a yellow filter. The experimental values were collected using FORS (fiber optic reflectance spectrometry) of specific points and hyperspectral imaging of the entire surface of the paintings. The specific values for the “yellow filter” for a given painting is taken from the absorbance spectrum of the removed varnish and then applied to the rest of the painting. After examining the spectra before cleaning, after cleaning, and the estimated virtual cleaning, it was clear that the yellow filter model for virtual cleaning was not enough to explain the spectral changes seen after cleaning. After varnishing the cleaned area, there was no change in color, only an increased brightness indicated by a rise in the near-infrared signal, so that alone did not explain the additional component missing from the yellow filter model.

I was thinking that even if it wasn’t spectrally perfect, could the yellow filter model at least be a good tool for an estimation of results? The example of the 15^th century Tuscan panel convinced me otherwise—while the yellow filter worked well for the blue areas, the model was a poor estimate for the red and brown areas. One component that is not taken into account with the yellow filter model is the effect of scattering by the varnish. Aged varnishes don’t just yellow, they also increase the scattering of light. Even with a scattering model included, the yellow filter model still did not accurately reflect the results of removing a yellowed varnish.

While virtual cleaning with simple “yellow filter” color correction in image processing software such as Photoshop is cheap and can be somewhat informative, it certainly is not a perfect model for varnish removal, even when the yellow filter’s spectrum is taken from the actual discolored varnish. The study has not considered selective cleaning, grime removal, or other nuances of cleaning paintings, which would only further complicate the spectral correction.