Ashley Jehle – AIC Blog Archives: Conservators Converse

45th Annual Meeting – Objects Session, June 1, “Well That Didn’t Work, Now What? Stain reduction on a 10th-century Iranian ceramic” by Claire Cuyaubère and Ellen Chase

Claire’s talk highlights a topic that I’m glad we conservators are beginning to talk about more openly – treatments that didn’t necessarily work. This subject also fit in nicely with the overall conference theme of treatment and innovation. Although some of her treatment steps did not bring about the desired results, Claire was successful in safely and aesthetically preparing the ceramic so that it can be exhibited at the Freer Gallery of Art.

The earthenware dish features a reddish-buff ceramic body, off-white slip, and transparent glaze, with minimal brownish-black and red inscription decorations. The ceramic was previously broken into about 40 pieces and restored, with multiple campaigns of adhesive and overpaint. The museum has records of one treatment in 1964, and while removing old repairs, Claire found evidence of at least two previous restorations which likely occurred before the object was acquired in 1954. The major condition issue was various types to staining, including general yellow and gray stains. Additional disfiguring stain lines were present a few millimeters in from the edges of the sherds, including some areas with two or three separate rows of parallel staining.

Claire carried out analysis in an effort to determine the cause of the staining. Using SEM-EDS, among other tools, she determined that the staining contained little iron and was primarily organic in nature, meaning it is likely not from burial but from the various restoration campaigns. Adhesive identification was inconclusive, likely because multiple types are present; however, Claire noted the presence of hide glue, some type of acetone-soluble adhesive, and possibly shellac. During testing, the staining did not appear to be soluble in a range of solvents, likely because of crosslinking. Soluble salts were also identified with a microchemical test for chlorides, although no salt efflorescence was visible. An iron-containing accretion on the back within the footring was likely from burial and was mechanically reduced to avoid transfer to other areas of the ceramic during stain reduction treatment.

Claire proceeded with stain reduction tests, following Bruno Pouliot, Lauren Fair, and Richard Wolbers’ method of three rounds of poulticing using a chelator, bleach, and a final rinse.* She ultimately chose sodium citrate (2% at pH 8) as the chelator because it was mild yet effective, and she used carbamide peroxide (20% at pH 8) as the bleach. For both of these steps, she used agarose gel (2%) as the poultice material, favoring its ability for controlled, localized application. The gel poultices were only applied to stained areas on the front surface of the ceramic.

Agarose gel is made by mixing the powder with water, heating to a low temperature, pouring the mixture out to cast, and then cutting into blocks when cool. The gel blocks can then be soaked in solution; for instance, Claire soaked blocks in the chelator for one hour before applying to the ceramic. Plastic wrap was used to cover the gel blocks while on the ceramic to reduce evaporation. For the final rinse, the sherds were soaked in baths of deionized water, which served to clear the chelator and bleach as well as desalinate the ceramic.

To complete the treatment, the sherds were joined using Paraloid B-72, which was also bulked with microballoons and fumed silica to fill gaps and losses. These areas were inpainted as the dish will be displayed in an art museum, as opposed to an archaeological context, and the curator preferred to have the losses integrated.

Although the staining was somewhat lightened, its appearance was not sufficiently reduced by the poulticing steps. Claire carried out many poulticing trials, but the staining proved tenacious and she did not want to take the treatment so far as to risk causing damage to the object. Although improvements were made, the curator still did not find the dish to be in exhibitable condition, since the staining lines were still visible and particularly distracting against the overall stark, white appearance of the ceramic. At this point, Claire decided to try painting out the stains, over a barrier layer of B-72. Although she did not like the idea of painting over the original ceramic surface, this seemed to be the only reasonable option for preparing the object to be exhibited and accessible to public. Painting light over dark and matching the surrounding off-white glazed slip must have been a challenging task. But in the end, conservators and curators were both pleased with the results!

Overall, I think Claire’s treatment was a success, and I look forward to seeing the dish on display when the Freer Sackler reopens their newly renovated galleries this fall.

* For more information, I recommend: Bruno Pouliot, Lauren Fair, and Richard Wolbers. “Re-thinking the Approach: Techniques Explored at Winterthur for the Stain Reduction of Ceramics,” 2013 in Recent Advances in Glass, Stained-Glass, and Ceramics Conservation, pre-prints of the ICOM-CC Glass and Ceramics Working Group Interim Meeting and the Forum of the International Scientific Committee for the Conservation of Stained Glass, Amsterdam. pg. 211–223.

44th Annual Meeting – Textile Session, May 15, “Inherent Vice in the Woven Structure of Northwest Coast Spruce Root Hats” by Sara Serban

We all love the topic of inherent vice. And in this talk, the topic is presented as it relates to basketry, hats, and an exhibition at a museum of Canadian social history.
Sara Serban, Objects Conservator at the Musée McCord in Montreal, spoke about painted and woven spruce root hats she prepared for “Wearing our Identity: The First Peoples Collection,” a ‘permanent’ exhibition planned to last five years (with rotations). The five hats selected for display were made between 1850 and 1920 by weavers from the Northwest coast of Canada, including the Haida and Kwakwaka’wakw cultural groups. In her talk, Sara discussed how the hats’ materials, complex woven structure, past storage and environmental conditions, and previous treatments relate to current condition issues and present treatment challenges.
Sara consulted with Isabel Rorick, a talented Haida weaver (see some of her work here), in order gain a better understanding of the materials and techniques used to make these types of hats. Sitka spruce roots are used for weaving because they grow in long straight lines. Roots are usually 3 to 20 feet in length, but can be as long as 50 feet. After harvesting, the outer layer of bark is removed from the roots by heating with hot coals, causing the bark to peel, and then pulling the roots through a split stick. The root is then split lengthwise one or more times. The interior pithy core is discarded, the inner layer is used for the warp of the hat, and the outer polished layer is used for the weft.
The processed roots are soaked in water and then woven from the top down using a combination of two-and three-strand twining techniques. Three-strand twining is almost always used for added strength at the crown of the hat, and twill twining is used to create geometric patterns at the brim. Continuous warps are used in the beginning, with additional warps added in as needed. A wooden disk form can aid in shaping the hat during weaving. An awl is often used to push the stitches together, and when complete, the hats are watertight.
Sara reviewed condition issues and previous treatments of the hats chosen for exhibition. As can be expected, the older hats are more fragile, and they all have experienced deterioration from low humidity. Darkening of spruce root, from cream-colored to dark brown, as a result of oxidation is a condition issue I was not aware of and seeing this contrast surprised me (compare the historic hat in the image above with the light color of this contemporary spruce root hat made by Rorick). Sara pointed out that while woven spruce root baskets are stored resting on their bottoms, hats are usually stored resting on their brims, and this positioning may cause additional stresses within the hat structure over time. She also noticed that certain areas, like the top disc, top edge (or turn), and crown, are more susceptible to breakage.
The majority of hats had undergone previous treatments (sometimes multiple campaigns), and many of these interventions caused further damage to the root fibers. For example, one hat had been repaired with a thick, raffia-like fiber that caused overall distortions in shape and breakage of adjacent root fibers. Sara questioned whether this type of mending was a traditional repair carried out when the hat was in its source community, or if it was later work. After a survey of spruce root hats in the museum’s collection, she found many had similar repairs, and because of this consistency, the repairs were likely carried out in the museum.
The museum’s conservation records indicate that treatments using methyl cellulose, wheat starch paste, and mixtures of Lascaux 360 HV and 498 HV were carried out in the 1980’s. Additionally, Paraloid B-72 in acetone was previously used to repair at least one hat because wheat starch paste was not found to be strong enough, although it was noted that acetone did affect the black paint on the surface. The common basketry repair technique using twists of Japanese tissue coated in adhesive was found not to be reliable, as these repairs often failed (e.g. the tissue lifted) not long after they were applied.
Examination of these past treatments helped Sara plan her treatment approach. Since the hats did not respond well to the adhesive mends of the past, she created mechanical mends using hair silk to hold the sides of the breaks together. She used a pattern of stitching with horizontal stitches on the outside of the hat and vertical stitches bridging the split on the interior. Prior to mending, she humidified distorted hats in a chamber with water and ethanol and then reshaped the hats, with the aid of carbon rod clamps (one of my favorite conservation tools). Tinted Japanese tissue, with twists to imitate weft strands, was used to fill losses on the hat’s crown. For loss compensation at the top turn of the hat, Sara first made molds of the woven surface using dental molding putty and then cast paper pulp into them. The paper fills were cut to shape, toned, and adhered with wheat starch paste.
After the presentation, an audience member asked about storage recommendations for the hats. Sara responded that ideally each hat would have a custom form with some type of cover that would offer protection from dust but not touch the surface of the hat.
This was one of several talks in the Textile Session that discussed more 3-D textiles (or textile “objects”), which were of particular interest to me as an objects conservator (see Muppets, Egungun,and a Digitally Printed Reproduction Sleeve). Also check out this blogpost about a related talk in the Objects Session: “The Aftermath of Meds: Removing Historic Fabric Tape from Tlingit Basketry” by Caitlin Mahony.

43rd Annual Meeting – Architecture Session, May 15, "The Power of Light! Using the Newest Laser Technology to Clean New York’s Oldest Outdoor Monument: The Obelisk of Pharaoh Thutmose III" by Bartosz Dajnowski

The Obelisk of Pharaoh Thutmose III, Before and After Treatment

The obelisk of Pharaoh Thutmose, also nicknamed Cleopatra’s Needle, is New York’s oldest outdoor monument. Matthew C. Reiley, Associate Director of Conservation and Senior Conservator at the Central Park Conservancy, began the talk by providing background information on the history of the obelisk. The stone monument was commissioned around 1450 BCE by Thutmose III to celebrate his 30^th year of rule. The red granite was quarried in Aswan and carved with hieroglyphs. It was one of a pair of obelisks that stood at the sun temple in Heliopolis. The monuments were purportedly toppled during a Persian invasion around 525 BCE and were later moved and re-erected in Alexandria by Romans around 12 BCE. In the 19^th century, one of the obelisks was given by Egypt to the United States. William Vanderbilt paid for the transportation of the monument to New York City. It traveled across the Atlantic Ocean in the hull of a ship and was raised in Central Park in 1881.
The first condition study and treatment of the monument came in 1885. The study noted damage from freeze-thaw cycles. Salt migration and deposition occurring over time, while the monument was in Egypt, had created microcracks in the substrate. Water infiltrating into these areas and expanding during freezing caused surface loss. Workers removed unstable fragments, and the surface was impregnated in paraffin wax, which over time trapped dirt and pollution. In 1983, the Metropolitan Museum of Art performed a scientific study, which found that the monument was stable and not aging at an accelerated rate.
In 2011, an Egyptian Antiquities official threatened to take back the obelisk, claiming it was not well cared for. This prompted the Central Park Conservancy’s project to document, clean, and stabilize the monument. Photographs were taken and color annotated to document condition issues. Cleaning tests, using aqueous methods, micro-abrasion, and lasers, were performed in order to find a suitable method for removing years of accumulated soiling and atmospheric pollutants that obscured the carvings. Based on these tests and in situ mockups, laser cleaning was chosen because it was controllable, effective, and did not damage the stone.
For the second half of the talk, Bartosz Dajnowski, Vice Director and Objects Conservator at the Conservation of Sculpture & Objects Studio Inc., described the laser cleaning methods. He listed some of the benefits of laser cleaning: no chemicals, no abrasives, no loud noises, and no public hazards or contamination to the surrounding areas. Unlike a laser pointer, the beam of this laser is focused to a point and then it spreads out so that the radiation diffuses past the focal point. The cleaning process is called laser ablation, and it works discriminately as it excites one material so that it separates from the substrate. Since laser cleaning is not a mechanical process, it is safe to use on fragile substrates. Bartosz noted that it is important to use the correct settings because if the laser is used incorrectly, it could damage the substrate, for example by melting bronze or shattering quartz and melting inclusions in stone. He also pointed out that adding water to a surface during laser ablation has a micro-steam cleaning effect as the laser turns water into steam. The water also helps reduce the effects of plasma formed by the laser, minimizing the possibility of phase changes in the iron within the stone.
Bartosz spoke about his prior experience and research with lasers, including work done during his graduate studies at Winterthur. Extensive testing and analysis was done on stone samples before laser cleaning began on the obelisk. Small fragments that had previously fallen off of the obelisk were cleaned and then examined by George Wheeler at the Metropolitan Museum of Art to confirm that safe laser cleaning parameters were being used.
Seven lasers were used to clean the entire stone monument and the four bronze crabs around its base. One of the lasers, called the GC-1, Bartosz built himself using a new design. With the other lasers, the pulses are emitted as line scanning, with a mirror alternating left and right, so the pulses come out like a machine gun firing back and forth. This creates hot spots at the edges, which can result in overcleaning or damage. Optical shields and other methods can be used to cut off the hot spots, although this decreases efficiency. In Bartosz’s new design, the laser pulses are emitted in a circular ring pattern, so the beam is constantly moving around in a circle. In this formation, there are no hotspots, and when the instrument is moved across the surface, the coverage area is exposed twice, which increases efficiency. Since this unit is also smaller, Bartosz was able to take it up to the top of the scaffolding. As others on his team used the line scanning lasers and worked from the bottom of the monument up, Bartosz worked from the top down. With his new laser, he was able to clean the same sized area in half the time!
With lasers, the level of cleaning is controllable, and Bartosz mentioned that the team was asked to try leaving some soiling in the recesses of the carving to increase the legibility of the glyphs. However, the soiling was uneven, and the carving had suffered previous damage, so it was not always easy to distinguish. An overall cleaning was carried out, although a few areas of soiling were left near the top of the monument for future analysis.
Following laser cleaning, fragile and unstable areas of the stone monument were consolidated. The 3,500 year old, 220 ton obelisk now stands cleaner and more stable for the future. In a fitting end to the talk, Bartosz noted the appropriateness of using light to clean and revive an ancient monument that was originally built to honor the sun.

42nd Annual Meeting – Joint Session: Objects + Research & Technical Studies, May 30, “Coping with Arsenic-Based Pesticides on Textile Collections” by Jae Anderson and Martina Dawley

Presenters:
Jae Anderson – MS candidate, Materials Science and Engineering, University of Arizona, member of Navajo tribe.
Martina Dawley – PhD candidate, American Indian Studies, and Assistant Curator for American Indian Relations, Arizona State Museum, member Hualapai and Navajo tribes.
Nancy Odegaard – Conservator Professor, Arizona State Museum.

Nancy Odegaard began by introducing this project to develop guidelines for the removal of arsenic from textiles utilizing a portable X-ray fluorescence analyzer (pXRF). She explained that a number of different forms of arsenic have historically been used on the collection at the Arizona State Museum (ASM). For this project, the team chose to focus on Navajo textiles due to the consistency in their materials and construction. In addition, they were able to consult with local Navajo (or Diné) weavers. Martina Dawley and Jae Anderson, who both worked in the ASM conservation lab on the project, presented the remainder of the talk.
Martina described her role in carrying out a survey of the Navajo textile collection, which includes blankets, rugs, and looms. She researched provenance information, produced documentation, and performed XRF analysis on each piece. One of the questions raised during the project was whether the rolled textiles could be analyzed with the pXRF while on the roll or if they had to be unrolled flat first. Interestingly, Martina noticed that the first reading on an object was diagnostic of the remaining readings on that object overall. If the first reading for arsenic was below 100ppm, most of the other readings were also below this level, and the corresponding trend was true if the first reading was greater than 100ppm. Therefore, for textiles with a lower initial reading, analysis was continued on the roll, meanwhile textiles were unrolled for more thorough testing if a higher-level initial reading was found. In the end, 17% of the textiles she tested were found to have levels at or above 100ppm, and the majority of these pieces (69%) were from the 1800’s. Forty-seven percent had less than 100ppm of arsenic, and 36% were found to have no arsenic.
Jae explained the experimental portion of the project in which the pXRF was calibrated and textile-washing methods were tested. First he described two inorganic arsenic species – arsenite, As(III), and arsenate, As(V). Arsenite is more toxic and is commonly in the forms arsenic trioxide and sodium arsenite. It can convert to arsenate by oxidation in wet conditions. For calibration and experimental testing, Jae wetted cotton and wool fabric samples with arsenite solutions of varying concentrations. Another variable tested was application method; he applied the arsenic solutions by droplet, dipping, and spraying, of which the latter two are traditional arsenic-pesticide application methods. During this step, he noticed the wool curled because of its hydroscopic nature, so he altered the experiment to utilize Chimayo hand-woven wool. He also added a surfactant to help with wetting properties and food coloring as a visual cue to see that solutions were applied evenly. Each fabric sample was analyzed five times, both wet and dry, with the pXRF in order to create a calibration curve.
Next, the fabric samples were washed in deionized water, and various conditional effects were tested, including temperature, pH, time, and agitation. The samples were again analyzed with pXRF and the results compared. Increasing the temperature and altering the pH of the wash water were found to have no effect on arsenic removal. The greatest arsenic removal overall occurred within the first 10 minutes of washing, and agitation caused a substantial increase in the effectiveness within the first five minutes. Therefore, the preliminary guidelines were washing for 10 minutes, at a neutral pH, with agitation, at room temperature.
After washing the fabric test samples, the team attempted to analyze the post-wash water with a paper indicator, however this test was not sensitive enough, nor did it indicate concentration. Inductively coupled plasma optical emission spectroscopy (ICP-OES) has the potential to quantify the levels of arsenic transferred to the wash water, and Jae noted that they are beginning to utilize this technique. Nevertheless, the post-wash water was found to contain less than 5 ppm arsenic, so it could be disposed of down the drain, according to municipal and federal regulations.
During the next phase of the experiment, three Navajo textiles were washed according to the preliminary guidelines. (Note that prior to washing, the textiles were documented, analyzed using pXRF, and their dyes tested for colorfastness.) After washing the first textile and finding the results did not correlate with their experimental data, the procedure was altered – the volume of wash water was calculated based on the experimental tests. The second textile washed was initially found to have high levels of arsenic (greater than 100ppm). Good results were achieved, with 96% of the arsenic removed and only minor dye bleeding. The third textile initially had low levels of arsenic (less than 100ppm) and less arsenic was removed during washing. Therefore, better results were achieved (i.e. greater arsenic removal was possible) when arsenic was initially present in higher quantities.
Overall the project surveyed 600 Navajo textiles and identified time-period and collector-dependent trends in arsenic concentrations. The team developed a cleaning protocol in which 95% of arsenic could be removed in high-arsenic contaminated textiles but with less effective results in lower arsenic containing textiles. The mass of the textile, the volume of wash water, as well as agitation and wash time (up to a point), were found to have an effect on results.
Several questions were posed in response to the presentation. One audience member wanted to know about the health and safety outcome of washing – could the textiles now be handled safely without gloves? Jae explained that the results would have to be evaluated by a medical toxicologist. Another attendee was interested to know if this technique could be used on a collection of fragile Egyptian textile fragments with a known history of pesticide treatment. Nancy replied that arsenic can be removed with washing, but the stability of the textile and its ability to withstand washing is a separate issue. Finally, someone asked if the arsenic species, arsenite vs. arsenate, could be identified on the textiles? Jae explained that the two forms are too similar to be distinguished here.
I look forward to hearing more results from this team as they continue exploring new experimental procedures and further developing arsenic removal techniques. Learn more about the ASM’s Preservation Division here.

AIC's 41st Annual Meeting – Objects Session, May 30, “Bon Appétit? Plastics in Julia Child’s Kitchen” by Mary Coughlin

I wonder what Julia would think about the current state of her kitchenware? In Mary Coughlin’s talk, “Bon Appétit? Plastics in Julia Child’s Kitchen,” Mary discussed issues she and her Museum Studies class faced while inside the Julia Child Kitchen exhibition at the Smithsonian’s National Museum of American History (NMAH). Mary is an objects conservator and professor at George Washington University. Her class carried out a condition survey of the exhibition as it transitioned from its original installation into part of the new FOOD: Transforming the American Table, 1950-2000 exhibition.
The kitchen was originally located in Julia Child’s Cambridge, Massachusetts home from 1961 to 2001 and was the setting of her last three television shows. When Julia donated it to NMAH, the museum accessioned over 1,200 objects, ranging from spatulas to a Rubik’s Cube. The kitchen was installed in the museum as Bon Appétit! Julia Child’s Kitchen, a temporary exhibition that was probably only meant to be on display for less than one year. But as is often the case with well-loved exhibitions, it ended up being on display for a decade.
Mary’s class worked within the exhibition, actually in Julia’s kitchen on view to the public, as they carried out the condition survey. It seems as though many of the museum visitors also wished to step inside the kitchen, as Mary humorously noted that they often heard the thud of visitors walking into the glass partitions. In an effort to provide outreach to the public, a curator was posted outside the kitchen to discuss the project with visitors. In addition, the students wrote blog posts about their experiences which can be viewed on the NMAH’s blog “O Say Can You See?” (For example, see one student’s post here).
After the condition survey, the class made recommendations for ways to incorporate preventive conservation into the new exhibition. Two of the main problems encountered in the old exhibition were dust and degraded plastics. The old exhibition did not have a ceiling, and the vents above the kitchen created a significant dust problem. This issue was particularly problematic considering that many of the plastics within the kitchen are oozing and sticky. The new installation is sealed on the top, and during Mary’s evaluation of the new exhibition six months later, she found a significant decrease in dust accumulation. One problem area was a large gap around one of the glass door covers, but it has since been gasketed to create a better seal.
Mary’s class also found evidence of fading and discoloration in plastics. For instance, the top surfaces of a set of rubber kitchen gloves had turned black, while the undersides remained blue. Mary placed mylar barriers underneath and between problematic plastics to prevent sticking and oozing on surrounding objects. And when the gloves were reinstalled in the new exhibition, the top glove was flipped in order to display the blue side, following the request of the curator.
Mary mentioned the curator’s desire for authenticity within the exhibition and that they wished to have all the original objects on display within the kitchen. While Mary’s class found evidence of plastic degradation, the museum continues to display the degrading plastics in a relatively similar environment as the previous exhibition (although the HVAC system is improved and dust is being mitigated. She also noted that the degrading objects were not causing damage to other objects). Mary’s talk raised questions that many museums and conservators must face, such as authenticity versus preservation? Does displaying original degraded objects or surrogate objects in good condition change the meaning or importance of the work? The answers to these questions may also be different within the context of a history museum as opposed to an art museum.
As I viewed images of oozing spatulas that are not dissimilar to those sold today, one of the questions I had (but didn’t get a chance to ask Mary) is whether there was any discussion with the curators about purchasing surrogate objects either to be displayed now or in the future? Maybe similar objects could be purchased now, while they are still readily available, and stored in more optimal conditions (dark, cold storage?) to be displayed later if needed.
I can’t help but wonder, what will the plastics in the exhibition look like in another ten years? And what would Julia Child think? Bon Appétit?