During the OSG tips luncheon, Ellen Promise, currently of Historic New England and formerly of the Isabella Stewart Gardner Museum, presented new techniques for filling and inpainting lacquer. The techniques, developed in collaboration with Jessica Choloros and Holly Salmon, are readily applicable to many types of objects, not just lacquer.
Lacquer objects, especially those damaged by light, have very sensitive surfaces; therefore creating fills in situ can be dangerous. In the technique presented, Golden Acrylic Regular Gel Medium in matte was mixed with acrylic paint to a frosting-like consistency. The tinted mixture was then cast out onto silicone release mylar. After drying, the paint film remains flexible, has the bulk required for a fill, and resembles the sheen of aged lacquer. The paint film is trimmed to shape with a scalpel and then adhered in place with fish glue or B-72. While the fill isn’t invisible at the edges, it is harmonious with aged, cracked lacquer and remains reversible.
Promise also described her experiments with inpainting lacquer, specifically the fine gold lines often found on these objects. While acrylic paint is easy to use, the texture and shine is often not a good match. Promise tested several other options – metallic pens and markers, metallic paints, and mica powders dusted over sizes. She evaluated the materials for color, texture, gloss, and adhesion to an acrylic substrate. For the object in her case study, a Chinese export table in the collection of Historic New England, she had the best results with a Decocolor opaque paint marker. The marker was a good color match and had a high pigment load without bulk. The marker, which produced a fine line, could be used directly on the fill, or the ink could be dispensed into a palette, mixed with solvent, and brush applied.
The third class of students has just been accepted into the CRAFT Program (Conservation Resources for Architectural Interiors/Furniture and Training) at the Palace Museum/Forbidden City in Beijing, co-sponsored by World Monuments Fund, the Palace Museum and Tsinghua University, where Greg Landrey worked as Conservator in Residence last fall. Landrey began his lecture by introducing the city of Beijing with a focus on the layout of the Forbidden City, in particular the Qianlong Garden (a cluster of 28 modest buildings in the northeast corner), as these interiors and their furnishings are used as teaching tools and selectively treated by the students in the program. The current student class size is approximately twelve students, and Landrey spoke through an interpreter when teaching. He also introduced the team of American conservators who have been teaching at CRAFT, and stressed that collaboration with the team was extremely important throughout the teaching process. Chinese experts also teach courses on wood identification, furniture history, and architectural history and preservation.
Landrey showed numerous photographs of the students at work in their classroom and lab, which appeared to be a large, modern, and filled with natural light. His curriculum began with conservation ethics and theory, using the “three-legged stool” example as a teaching tool. Other subjects included the nature of wood, building hygrometers to see wood movement in action, wood technology, loss compensation, and casting. Landrey said that learning went both ways, because the students shared their knowledge of craft approaches and techniques with him throughout the semester. Treatment was also a teaching tool, with the students working as a class to document, analyze, and clean a three-part screen from the Qianlong Garden quarter of the Forbidden City. Landrey also had the students carry out drawing exercises each week to hone their drawing and observation skills, and he showed some particularly lovely examples to the audience. Field trips were taken to museums in Suzhou, as well as to the studio of a traditional lacquer artist and brocade museum with active looms.
Landrey had the students regularly read the AIC Code of Ethics as well as the Principles of Conservations of Heritage Sites in China, and expound on passages they felt were particularly meaningful to them. The student answers were shared with the audience as they were very insightful and showed how much they had learned. The goal of the program is to produce conservators to serve projects in China, and eventually the CRAFT curriculum will be entirely taught by Chinese conservators and scholars.
This talk was peppered with wonderful images and insights into Landrey’s life in Beijing, including the lively chaos of the city streets, Tai Chi being practiced by the students and staff in the morning, and the reverence the culture has for trees, which apparently made him feel a little bit more at home.
The speaker began with some general information about Romania, where more than 12,000 historical wooden churches survive, eight of which are UNESCO sites. In the north, one distinguishing feature of the churches is a bell tower atop a sharply sloping roof, for drainage due to the abundant rainfall in that area. In the drier south, there are no bell towers and the roof is lower, more in the style of a traditional Romanian house. Focusing on Buzau County (located between Moldova, Transylvania and Wallachia), most of the churches are in the northwest region, with thirty-two historic churches of particular importance. The speaker carried out in-situ investigations of these churches in the summer of 2013, and these investigations appeared to consist of archival research, visual investigation and documentation. Most of the buildings are of wood beam construction with a rectangular floor plan that follows the plan of the Orthodox Church, and include a porch at the front entrance. Many contain interior paintings on sheet metal or on wood, executed in oil (on metal) or tempera (wood). Some exterior decoration survives in the form of shallowly carved motifs. The speaker spent a few minutes presenting each church, usually showing an overall exterior photograph, a floor plan, any specific construction details that made it unique, as well as an abbreviated history of its restoration. Some images of the interior paintings were also shown. The state of conservation of the churches was not discussed, although it was a question afterwards. The speaker answered that while some of the churches are still in use, most are completely abandoned and in need of care.
I was interested in this talk because it seemed an interesting intersection between textiles and objects together with the complications of working on objects that are still in use.
MJ discussed the set of challenges of working with historic stage scenery: climate, use, lack of funds, space to do treatments, ect. The “Curtains Without Borders” team (started 15 years ago in the state of Vermont) of conservators came up with a standard method of treatment that could be applied, with some differences as need, to the stage curtains. The typical treatment consists of: on-site technical examination, cleaning (vacuuming and dry sponging), mending tears with patches of muslin w/B72, inserts to areas of loss, consolidation of edges (all sides reinforced with muslin w/B72), structural support at top edge if necessary and reattachment of bottom roller, paint consolidation (sprayed B72), in-painting of losses and reinstallation with volunteers or professional riggers as needed. All work is done onsite by conservators and a team of local volunteers (with at least 2 at all times). Many conserved curtains have been revisited over the years and additional issues have been attended to. Issues have mostly come from handling of curtains once they were re-installed.
The project has been a success all over New England- with more requests coming in from all over the country for help. There are plans to continue the project and expand territory.
Hubert Baija, Senior Conservator of Frames and Gilding, has been responsible for overseeing the conservation of the frame collection at the Rijksmuseum Amsterdam since 1990. Numbering over 7000 frames that are now accessioned and inventoried as works of art in their own right, Baija has had the opportunity to treat frames of different styles and condition issues. During his presentation, he discussed three treatments. He emphasized the need for close study and observation of the original materials, understanding the appearance and intended effect created by the frames in their original lighting situations, and choosing reversible materials in a creative way. He noted that a treatment need not be overly involved to successfully reintegrate the gilding.
His first case study was the treatment of a Louis XVI oval frame (1777-89) that was original to the portrait it framed. The discussion addressed the past practice of covering worn gilding with bronze paint, that later had been retoned with a dark glue/pigment layer to match the discolored bronze. These layers significantly altered the intended appearance of the frame, by negating the play of dark, light, and reflectance across the complex surface. Baija demonstrated that by removing the glue and bronze paint layers (using simple solvent mixtures), only a minimal amount of inpainting was necessary to reintegrate the gilded surface. While the improvement to the frame was impressive, the appearance of the painting when displayed in the frame was also significantly improved by the intervention.
Baija’s second example demonstrated his skill as an artisan, his keen observation, and his determined investigation of a little know technique that had previously been overlooked. He stylistically identified a pair of auricular frames carved from lindenwood to c.1660-1665. Both frames had significant worm damage, had lost smaller portions of carved decoration, and were overpainted and overgilded. Only small areas of the original gilding remained intact–between 5 and 30%.
The original gilding was done using a type of mordant gilding that is not known from historical texts and has not been identified before. Using SEM-EDX imaging of cross sections, the technique was characterized: the bare wood was prepared for gilding using a thick glue layer (1 mm Th), followed by a pigmented emulsion layer, to which the gilding was applied.
Noting that the tradition of gilding in the Netherlands had been lost since the 1580s, and that more traditional (and stable) gilding techniques would not be reintroduced to the Netherlands until later in the 17th century by French Huguenots, Baija surmised that this unusual technique was in use—only in the Netherlands–for a relatively short period of time. After his initial characterization of the technique on these frames, he has since identified other examples on Dutch frames and furniture that are stylistically dated to 1650-1680. Because the technique was inherently unstable given the response of the thick glue layer to changes in humidity, many pieces gilded using this technique have subsequently been overgilded.
After cleaning the frames of non-original layers, the carved losses to the wood were reconstructed using paper mâché /methyl cellulose mixture, mixed with water. The material can be handled like clay to buildup the appropriate forms. The paper mâché shrinks slightly, allowing for application of Modostuc finishing layer. Because an isolating layer of Paraloid B-72 had been applied to the original wood surface, the paper mâché fill remains easily reversible. Shallower losses were also filled with Modostuc.
Most creative was Baija’s approach to inpainting to create the illusion of distressed gilding. Noting that the original thick glue layer would only be very slowly soluble in water, gouache was chosen to provide a brown base tone over areas of lost gilding and structural reconstruction. Islands of worn gilding were recreated using mica pigments mixed with Schminke watercolors, masterfully creating the illusion of a worn gilded surface. Final toning was done using ethanol soluble dyes in Mowilith 20. Toning could also be done using Gamblin Conservation Colors, PVA, etc. Coincidently, the dating of the frames was confirmed and the paintings and frames temporarily reunited, when an early 20thC. photograph of the frames paired with their original paintings was identified. The paintings are signed and dated 1661.
In his final example, Baija described an approach to reintegrating an area of loss in the gilding on a panel painting by Lorenzo Monaco, Stigmata of St Francis, c.1420. The area of damage was on a stepped join that was filled using Modostuc and prepared for gilding with acrylic bole from the Kolner system. Baija emphasized the importance of selecting a gold that was the correct color, but lighter in tone than the final appearance needed. He noted that any toning layers/coatings would take away from the intended appearance of the gilding—imitation of solid gold. By simply inscribing the cracks in the newly gilded loss, using horizontal lines to disrupt the vertical disruption of the loss, the gilding was effectively knocked back to the correct tone. Minor glazes to create the effect of dirt in the cracks were then applied.
Each of these treatments demonstrated issues that are common to conservation of gilded objects. Gilded surfaces are often overgilded or painted with bronze paint to recreate the impression of gold. Alternatively, gilded surfaces tend to be toned dark, either to reintegrate corroded bronze paint or to tone back gold that may seem too garish or is disrupted in other ways.
Baija’s approach is one that brings back the appreciation of frames as works of art, rather than as just accessories to paintings. It emphasizes the need to understand the original and aged appearance of the gilding, and to recover what is left of the original. His approach is one that acknowledges the frames—like objects and paintings–should be treated in reversible ways, using conservation materials distinguishable from the original materials. It thereby breaks from the traditional approach of regilding frames using traditional materials and techniques. He encourages the exploration of new materials, the use of reversible layering systems, and acknowledging the patina of time and use. An overall theme of the talk was one of reintegrating the gilding only to the level of the best-preserved area of original gilding.
For those interested in furthering their understanding of gilding and approaches to gilding restoration, Baija teaches two workshops at the Campbell Center in Mt Carroll, Illinois. “Traditional Gilding” and “Gilding Restoration” combine lecture and practical work in the studio. I attended both workshops over the last two summers, and as a result have improved my treatment approach for gilded frames. I highly recommend them.
Those who have beheld the Hall of Northwest Coast Indians at the American Museum of Natural History and its extraordinary “totem poles” will instantly recognize the potential scope of any study or treatment of such massive artifacts.
These objects are housed in the earliest wing of the museum, curated at its inception by Franz Boas, “the father of American Anthropology”, who organized the early acquisitions of the museum according to a revolutionary argument: that of “cultural relativism” in opposition to a chauvinistic, social-Darwinist organization that put “primitive” peoples at the bottom of an evolutionary tree, the pinnacle of which was white America. Today, this hall holds a landmarked status and remains relatively unchanged, as the poles are very hard to move.
Ten years ago, a renovation of the hall was proposed. Although the recession thwarted plans, the objects were still in need of stabilization and aesthetic improvements. Because this project—from its inception, through the research, testing, and execution stage, was so expansive—Samantha Alderson reminded her audience that her talk could only represent an overview of a four-year process. Those interested in a specific aspect of the project can look forward to in-depth, forthcoming publications.
One of the more important aspects of the research phase, and a professional obligation that is indispensable to the curation and conservation of native materials, was the consideration of ethical issues and provenance information. Most of these pieces entered the collection between the 1880s and the 1920s, and the majority has been on continual, open display since their arrival. Their presence in AMNH’s collection is widely acknowledged to be ethically complicated in itself, representing an era of unscrupulous dealing in Northwest Coast artifacts. (To read more about “Indians and about their procurable culture,” consult Douglas Cole’s, “Captured Heritage: The Scramble for Northwest Coast Artifacts,” about the coincidence of a taste for these native artifacts and the establishment of many of the country’s foremost natural history collections. (p.xi)]
The carvings, including the carved columns most commonly described as ”totem poles,” would have had numerous functions within their originating cultures: house frontal poles holding entry portals to buildings, interior house posts, welcome figures, memorial poles, and mortuary posts [For a technical study on these types of carvings, please consult “Melissa H. Carr. “A Conservation Perspective on Wooden Carvings of the Pacific Northwest Coast.” Wooden Artifacts Group Postprints. 1993.].
To further hone their understanding of provenance, the 2009 CCI “Caring for Totem Poles” workshop in Alert, Canada, allowed the authors to travel through British Columbia with curatorial consultants, native carvers, and native caretakers, in order to study the techniques of manufacture. It was also important to keep abreast of the expectations of the native communities that might be borne out over the course of any treatment intervention or re-installation campaign.
The original aim of this project was to provide structural stability to those carvings which exhibited highly deteriorated surfaces caused by the weathering and biodeterioration in their original environment. These instabilities were often exacerbated by inappropriate environmental conditions and restoration interventions in the museum. The most significant issue requiring treatment was the presence of wood rot, insects, and biological growth, present in the original environment and continuing to run their course.
Although climate control was installed in 1995, soot from the age of coal heaters and lamps still blanketed the inaccessible areas of the objects. Dust from visitor traffic also dulled them, as the hall is adjacent to the entrance to the IMAX theatre. Routine and well-intentioned cleaning was ineffective against a century of accumulated grime and dust and was causing surface loss.
As there is no barrier between the objects and the visitor, touching has caused burnishing and scratching. The unfinished wood readily absorbs skin oils; and graffiti and adhered chewing gum had also become a most-unfortunate problem.
Early interventions after acquisition had caused condition problems of their own, as old fills had a hardness or density that is inappropriate for soft, weathered wood. These fill materials were only becoming more ugly, unstable, crumbly, and cracked with age.
All of these factors, taken together, provided a huge impetus for treatment.
To begin the treatment-planning stage, the conservators at AMNH performed examinations under visible and UV radiation and mapped the observed conditions and materials using a streamlined iPad-based documentation protocol. In some cases the restoration materials observed provided evidence of institutional and condition history. Although there were almost no previous treatment records of these objects, comparison with archival photographs of many of the objects showed the rate of deterioration since acquisition and provided clues as to dates of interventions and installation history.
In summary of the object-treatment stage, vacuums and sponges were first used in an attempt to reduce some of the dinginess of the surface and to increase the legibility of the painted designs. The many resinous and waxy coatings had trapped so much dust, however, that this treatment did not always have a satisfactory result.
The question of solvent toxicity held sway in all aspects of treatment, as operations were completed in makeshift spaces outside of the lab, due to the size of the objects; these areas had no fume-extraction infrastructure. Luckily, plaster fills could be softened with a warm-water-and-ethanol mixture and carved out.
Butvar B-98 and Paraloid B-72 were selected as potential consolidants and adhesives. A 5-10% Butvar B-98 solution in ethanol (i.e. without the toluene component for safety concerns) was used for surface stabilization, and Paraloid B-72 in acetone was used for adhesion of splinters and detached fragments.
Fills were designed using different materials depending on the location on the object. These were intended to reduce damage during installation, display, and regular maintenance. If the fill was not visible, shapes were cut from Volara, beveled, and adhered in place with Paraloid B-72 along the edges. These were often necessary on the tops of the poles to cover the deep voids of deteriorated wood. Some losses were back-filled with tinted glass micro-balloon mixtures of different grades and different resin-to-balloon ratios where appropriate. As some paints were solvent-sensitive, certain fills required the use of Paraloid B-67. The final fill type was a removable epoxy-bulked fill to compensate for deep losses in visible areas. These areas were first filled with polyethylene foam to prevent the fill from locking in. The edges of the fill area to be cast were protected by tamping down teflon (plumber’s) tape which conforms nicely to the wooden surface. West System 105 Epoxy Resin—with “fast” 205, “slow” 206, or “extra-slow” 209 hardeners—was used in different proportions to 3M glass microspheres and pigments to give fill material with various hardness, curing-times, textures, and colors (See Knauer’s upcoming publication in ICOM-CC Warsaw 2013 for more details). This method is notable for its invisibility, its reversibility, and its rejection of phenolic micro-balloons, which are an unstable and unsuitable and were historically used for such a wood fill merely for their brown color. Once cured, the bulked-epoxy (and the plumber’s tape) were removed and the fills were then tacked into place with B-72 to produce an aesthetically pleasing and protective cap.
Many losses which were previously filled were left unfilled, as would have been the case it they had been collected and treated today. Crack fills were incised so as to retain the appearance of a (smaller) crack.
Once the surface and structure was stabilized with the consolidation and filling operations, the team turned their attention to the various paint films to be cleaned. Many of these were proteinaceous but some were more similar to house paints. This data was consistent with the ethnographic findings and with current native practice. No preparatory layers were used, and the pigment layers were often very lean.
PLM, XRF, and SEM-EDS, as well as UV-FL imaging, thin sections, and analysis with FTIR was undertaken. Some binder analysis was also possible, but this was complicated by historical treatments. Interpretation of epi-fluorescence microscopy results was also thwarted by the presence of multiple coatings, the inter-penetration, -dissolution, and bleed-through of layers. As many as four different types of coatings were identified, and understanding and addressing the condition issues caused by these coatings became a primary concern. Cellulose Nitrate was often applied to carvings in the early 20th century. Whether this was to refurbish or protect, it has developed into a dark-brown layer which is alternately hazy and glossy and which obscured the original surface appearance. Lower regions evidenced PVA or PVAc on top of the Cellulose Nitrate. Shellac and dammar are present in isolated locations, as is an orange resin which eluded identification (even when analyzed with GCMS).
Although identification of these coatings was attempted, removal was not originally planned due to the difficulties designing a solvent system for its reduction, considering the variation in sensitivities, the interpenetration of the layers, and the unknown condition of the original paint films beneath. This plan changed when the poles were deinstalled for construction.
The treatment design was largely aided by the isolation of four house posts in the collection made by Kwakwaka’wakw artist Arthur Shaughnessy.
Commissioned by AMNH in 1923, these had never been installed outdoors but which had been coated in the same manner and exhibited in the same space. This allowed for the development of controlled methods for coating reduction.
A Teas table (or Teas chart) was used to identify potential solvents or solvent mixtures, which were tested over every color and monitored for any leaching or swelling. These initial tests were deemed unsuccessful.
In areas without paint, film reformation with acetone reduced haziness or glossiness. Where the coating was completely removed, the wood was often left with an over-cleaned appearance which necessitated some coating redistribution with MBK, MEK, and propylene glycol. Wherever possible, gels were used to reduce the exposure to toxic solvents. In painted areas, the large variation in solvent sensitivity, the inconsistency of media binders, the varying porosity of the wood, and the changing direction of the wood grain required that the conservators work inch-by-inch. DMSO, a component of “safe” stripper, and NMP were controllable over certain colors but caused considerable swelling.
February 2012, the museum saw the reinstallation of the Shaughnessy poles, marking the effective conclusion of the testing period and the successful management of a challenging triage situation by conservation staff.
It was Kwakwaka‘wakw artists like Arthur Shaughnessy who kept carving traditions active when the Canadian government prohibited the potlatch ceremony in 1885. The ban was lifted in 1951, after AMNH’s acquisition of the house posts.
The completion of treatment represents an important opportunity to educate the public: Although these monumental carvings are exhibited in a historic wing of the museum, we need to dust them off and remember that these carvings represent very, active traditional practices and communities.
There is still the need to develop more systematic solvent strategies, as well as to consult with a paintings conservator. But it is clear that these objects stand to look much improved after the grime and coatings are removed or reduced and the objects are thoughtfully reintegrated with a well-designed fill system. Thanks to the remarkable talents of the AMNH team, these stately creations are finally commanding the respect they deserve.
Alex Carlisle presented a fascinating and detailed treatment of the pulpit in Fort Herkimer Church, German Flatts, New York (http://fortherkimerchurch.org/7.html). The church has a long history; the current structure dates to 1767, with many additions and expansion in war and peacetime. The pulpit was added in the early 19th century, and seems to be completely unique; it is made from white pine, but nothing is known about the workshop.
During a recent, major renovation of the church, white paint coating the pulpit was partially sanded off and discovered to be covering polychrome decoration. At this point, Carlisle was asked to work on the project, to remove the remaining white overpaint and preserve the original polychrome layer. At least one coat of white paint was lead-based, and very intractable; the majority of this was mechanically removed. Fortunately an older resin coating layer was present, and the lead white paint tended to cleave off at the interface.
Once the white overpaint was removed, the remaining original surfaces were consolidated and coated with a barrier layer. Losses in the polychrome ornament were inpainted to re-create the original decorative effect. So far the base and main section of the pulpit have successfully been treated; the canopy awaits funding to complete the project (keep an eye out for part 3!)
Nolley and Gillis treated a 17th century Pennsylvania German shrank which is a rare example with surviving original painted finish including faux burl wood graining and colorful decorative ornaments.
Shrank is a German word for wardrobe; many such cabinets were made in America by immigrants, using locally available woods. As with other types of furniture, these would sometimes have been faux painted to imitate a fancier wood with more elaborate carving or decoration; grain painting was a common decorative technique. Due to their utilitarian nature, original finishes on early examples seldom survive.
Cross-section analysis showed that the Chipstone shrank did have original paint, but with large areas compromised by fire damage and wear from use. This led to the initial overpainting in the early 19th century, followed by several consecutive paint treatments over the years, including an opaque, gray-blue colored casein based paint. This gray-blue layer proved to be very intractable, particularly over areas that were burned or highly worn. Cleaning solutions with chelators were able to remove the majority; agar gel was used for local cleaning around sensitive areas. Older oil-based coating layers actually acted as a resist to prevent the cleaning from going too far.
Completed with varnishing, waxing, and selective inpainting, the treatment was able to successfully expose original decoration and give a sense of the shrank’s intended appearance.
Catherine Coueignoux presented an exciting treatment of the Augustus Rex (c.1750) writing cabinet in the collection of the Victoria & Albert Museum (W.63-1977 http://collections.vam.ac.uk/item/O74665/writing-cabinet-kimmel-michael/# )
The elaborate ormolu mounts had been previously re-gilded. Before treatment were coated with a thick layer of dirt and dust over a shoe polish-like wax treatment, which was possibly added to dull the appearance of the bright new gilding. All other metal components were corroded, and the wood and marquetry had all been stripped and refinished. Curators wished the treatment to result in a bright, nearly-new appearance as it may have looked when newly restored (the previous refinishing and regilding probably occurred while owned by the Rothschild family).
Spotty corrosion on metal components that could not be removed was treated locally where possible. EDTA gel and BCA gels were tested but unsatisfactory- cleaning not enough, or too well. Coueignoux was able to use rottenstone to spot clean dark areas, leaving a layer of light corrosion sympathetic to surrounding areas. In some places, the corrosion spots were left untreated.
The removable ormolu mounts were cleaned using dry ice pellets, a new method for the lab. Their system uses a block of CO2 dry ice which is shaved into pellets and sprayed onto the surface of the object using an air compressor with a custom nozzle. The CO2 pellets expand on contact, providing a gentle mechanical cleaning. By moving quickly along the surface, they were able to avoid excessive cooling that would result in condensation. Acetone and a hairdryer were on hand to remove any condensation that did form. Other labs using CO2 cleaning include the Getty and the Smithsonian.
In the case of the ormolu mounts, CO2 cleaning was fast, safe and effective and removing the unwanted wax and dirt- 150 mounts were cleaned in only seven hours! Obviously this method is not appropriate for many objects and materials, but may be a convenient choice for more conservators in the future.
In his presentation, Alan Miller, Assistant Conservator in Paintings Conservation at the Metropolitan Museum of Art in New York, showcased recent developments of spring-loaded secondary supports attached to the back of panel paintings.
He began by reviewing how usual 19th and 20th century treatment of warped panel paintings involved severe thinning of panels along with the application of wood “cradles” on their backs to straighten them and provide “support”. This portion of the presentation wonderfully complimented Karen French’s earlier talk on the evolution of the structural treatment of panel paintings at the Walters.
As Karen did in the morning, Alan discussed the consequences of past treatments on the panel and its painted surface. New treatment approaches have evolved over the past two decades with the development of flexible supports attached to the back of panels, allowing for the natural curvature of the wood and its movement in response to changes in relative humidity. Specific consideration was given to previously thinned panels, very vulnerable once their cradle is removed. Alan provided a review of the development of the spring mechanisms they developed with George Bisacca these past years, referring to the Getty Conservation Institute’s panel paintings initiative (link: http://getty.edu/conservation/our_projects/education/panelpaintings/panelpaintings_component1.html)
The presentation was generously illustrated with images of the various spring mechanisms developed at both the Istituto Superiore per la Conservazione ed il Restauro (ISCR) and later by Bisacca and Miller, explaining the pros and cons of each. For instance, the earlier conical spring designed at the Istituto allowed for much movement but required thickness of the wooden strainer attached to the back of the panel painting, an issue in terms of flexibility of the strainer, not to mention weight and volume. On the Met’s most recent strainers, which are much thinner, grooves are cut cross grain and filled with a silicon based material for added flexibility. Miller emphasized the importance of the number and placement of the springs attached to the back of a previously thinned panel.
He listed the criteria established for the development of spring mechanisms specifically designed for previously thinned panels: springs should be as small (contained) as possible to allow for a thin strainer, easy to adjust, economical and re-usable. Most recently their work has focused on a thin laser cut disk spring, associated with a flexible threaded nylon screw, which allows light weight, flexibility and fine adjustment.
This talk provided very valuable information on recent developments in the treatment approach of wooden panels, applicable not only to paintings but possibly to furniture or architectural wooden panels.