Art conservation that does more harm than good

Hindsight is 20-20, as they say. This week Art Daily* reported that a widespread preservation treatment, developed to help canvases survive humid environments, actually makes paintings more vulnerable when humidity levels soar.** “The wax-resin treatment was enormously popular in Europe and the U.S. during the 1950s and 1960s,” says Cecil Krarup Andersen at the Royal Danish Academy of Fine Arts, who made the discovery. “Many masterpieces, such as Rembrandts and Van Goghs were preventatively treated with wax-resin linings to help protect the artwork from humidity degradation. The treatment does exactly the opposite.” Anderson has just wrapped up her PhD work on the topic, a research project that began because museum staff at Statens Museum for Kunst were trying to figure out why Danish Golden Age paintings treated with wax-resin were not resisting the insults of time as well as they should. I needed a little background on wax-resin treatment which Andersen kindly provided: It was popularized in the 1800s by a Dutch restorer named Nicolaas Hopman. One of the first masterpieces to be treated was Rembrandt’s Night Watch in 1851. The overall motivation was logical: Hopman thought that coating the back of a canvas with beeswax and an extra layer of canvas would act as a protective support for the painting. Later on, he and others began mixing tree resin in with the wax because it added stiffness. Throughout the 20th century, the treatment gained popularity. Until the 1970s. That’s when conservators started talking about the importance of reversibility, the idea that any conservation treatment on artwork should ideally have an undo button, just in case a treatment turned out to have unforeseen, negative, long-term impacts or in case a better treatment came along sometime in the future. At a conference in Greenwich, England, in 1974, a group of high profile conservators decided that wax-resin treatments were not reversible and should be discontinued, Andersen says. Wax-resin treatments were gradually phased out, but it was too late for thousands of masterpieces that had already faced the hot iron. Initially conservators used irons to melt the wax-resin on to the back of paintings, upon which they adhered the extra canvas layer. Then in the 1950s, specialized heating tables were invented. These tables could uniformly heat the wax-resin and seal the back lining to the painting “in no time,” Andersen says. They made it easy for conservators to overdo it, she says. (As an aside, Andersen says the treatment additionally flattened out the texture in some paintings.) Another reason 1970s conservators became nonplussed with wax-resin was that the treatment actually changed the color of paintings. Sometimes the hot wax and resin would...

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Wedding Hiatus

Artful Science is in the middle of a two week hiatus as I prepare madly for my imminent wedding. (Yay!) In the meantime, it seems somewhat fitting to direct you to a previous post about mysterious green stains on a WW2-era wedding dress. Also, since my silver wedding dress makes me look pretty much like a space bride (but thankfully *not* this one), I figure a post on spacesuit conservation is also a propos. Artful Science will be back to regularly scheduled programming in early...

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Sweat-Stained Artifacts

We all sweat. Some of us do it rather profusely, particularly when life suddenly gets a tad more exciting or stressful than usual. Such as on your wedding day. Or during military combat. Or on your coronation day—if you happen to be royalty. Clothing worn during historically important events often finds its way to museums, and that’s when a textile conservator will take a good look—and possibly a deep sniff—in an outfit’s armpit region. According to four textile conservators who humored my—as it turns out—not so absurd sweat stain inquiry, armpit areas can be colored yellow (no surprise there), but also green, orange, brown and red. The quirkiest sweat stain reported was “a grey-green tide-line stain… with a pinkish interior.” Staining can depend on a myriad of factors, such as the individual wearer’s sweat chemistry, the fabric, the dye, and whether the person was wearing deodorant or antiperspirant. Consider the case of a World War II wedding dress that crossed Jessie Firth’s conservation table at the Australian War Memorial. Worn by five different women in the 1940s, the pretty beige dress had green armpits. Firth figured out that the culprit was a decorative copper thread in the dress that was corroded by the armpit sweat, producing the green patina you normally see on copper-plated architecture. Sweat is a rather complicated mixture of proteins, fatty acids and other molecules, but the lactic acid, salt and ammonia constituents may have all helped corrode the copper wire so that the dress stained green. Proteins in sweat are probably to blame for the most common yellow stain. These proteins may become tightly fixed to the fabric by the aluminum salts in deodorants and antiperspirants–but this is still debated. Some red stains may come from an early formulation of a popular antiperspirant called Odorono (Odor-Oh-No!), which was launched in the 1910s and was initially red in color. (Random aside: The Who once wrote a satirical song about Odorono. But I digress.) The question is what to do about the sweat stains? There’s the increasingly popular “hands-off” philosophy in art conservation circles which argues that even the most benign-seeming treatment may cause some long-term harm, so it’s best to avoid any superfluous interventions on artifacts. In addition, the sweat itself may have some important historical value. For example, if Queen Elizabeth II’s coronation dress had sweat stains, no conservator in their right mind would remove that important historical information about her emotional state at the time—although it could just be information about the June day’s ambient weather. (But is it ever really that hot in England?) On the other hand, decade- or century-old perspiration can weaken a garment’s underarm area...

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Arsenic Contamination Of Artifacts

A few weeks ago I got to touch the hairy underbelly of an armadillo. Even though it hadn’t been alive for some time, I was still pretty chuffed about the whole experience—I mean, it’s unlikely I’ll ever have such an intimate moment with an armadillo again. The beast in question had been briefly removed from its basement cupboard home at the North Carolina Museum of Natural Sciences as part of a behind-the-scenes tour during the recent Science Online conference. The experience of handling a stuffed armadillo was not just exceptional because it’s a stuffed armadillo. The experience was exceptional because it’s rather unwise to spontaneously handle animal or plant-based artifacts found in museum storage rooms. Until the 1970s, many biologically-based artifacts were doused with arsenic (as well as lead, mercury and some organic pesticides such as DDT) to keep insect and microbial invaders at bay, explained Lisa Gatens, the NCMNS curator of mammals who let me and others on the tour touch the animal. (For the record, the armadillo was safe.) Since the practice of adding pesticides to biologically-based artifacts began in the 1800s, there are an awful lot of contaminated museum artifacts out there. And many have levels of arsenic that could pose a problem to human health if handled without protection. A quick Internet search brought me to Nancy Odegaard, a conservator at the Arizona State Museum, who has spent a huge chunk of her career trying to come up with solutions to this contamination problem. Odegaard told me that concerns about contaminated artifacts initially arose in the 70s and 80s, during that era’s increasing awareness about the dark side of some commonly used chemicals. The museum community began to worry that conservators and curators working with artifacts might be at risk, not to mention museum goers participating in hands-on exhibits. Then in 1990, the US government launched the Native American Graves Protection and Repatriation Act. At this point, museums began returning artifacts to Native Americans who might start using the pieces in ceremonies instead of storing them behind glass. Since many of these artifacts were made of leather, feathers and other biologically-sourced materials, they too had been subject to toxic anti-pest measures. The potential health risk to Native Americans was very concerning. “I lost sleep thinking about this,” Odegaard says. “In particular, you worry about head-dresses, which are worn near the eyes, nose and mouth–this is ground zero for contamination entry.” Odegaard started organizing seminars and conferences with Native American leaders, conservators and medical researchers to discuss contamination and how to assess health risks. (She is an author on this 2000 JAMA letter entitled Arsenic Contamination...

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Greening Up Conservation Science

Cultural heritage is important so valuable art and artifacts should be protected at any cost, right? Not so, says May Cassar, the director of the Center for Sustainable Heritage at University College London. Most museum, galleries and archives take it as a given that air conditioning and pollution filtration are a must for keeping valuable collections in comfortable living conditions, she says. “But air conditioning and particularly pollution filtration come at a very high cost–not only to institutional budgets but also from an environmental point of view” because fossil fuels are consumed to drive these systems, Cassar explains. “To me it is a double standard to damage the environment outside but protect the environment inside for collections.” She’s trying to encourage people in cultural conservation careers to consider the environment outside–and not just around valuable collections. So for example, Cassar advocates that museums in temperate climates–such as the UK–accept some minor risks to collections if there is a possible gain for the environment. For example, a museum might normally use air conditioning to keep humidity in between 50-60%. If the building’s internal humidity would normally only ever range from 40-65%, reaching the outer extremes only rarely, it could be fine for the museum to eschew humidity control without substantially increasing risk to the collection, she says. Of course, it’s true that some museums don’t have the luxury of a temperate climate… Consider the soul-destroying humidity of Washington DC’s summer months (I barely survived two of them), or the corrosion potential from the high salt concentrations found in the air around ocean-side museums, or the problem New York City’s sooty air pollution raises for valuable collections. But there may be other ways for museum, archive and gallery staff to go green. To name a few: Conservation scientists are evaluating whether enzymes can be used instead of solvents to extract adhesives during textile conservation. Researchers are looking for paint and varnish removers that don’t contain dichloromethane, which isn’t entirely awesome to inhale. They are also investigating low-energy museum lighting options and possible non-pesticide ways to control insect invasion of wood and textile artifacts (such as brief exposures to sunlight). One of the stumbling blocks to getting conservators on-board with environmentally friendly alternatives is that they are unwilling to give up tried-and-true methods for riskier ones, especially on objects of great cultural value. “Although in theory using green chemistry should produce better results for the environment, we don’t know whether it produces as equally good results for collections,” Cassar says. But doing the science to find out “is a risk worth taking,” she...

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Dating Silk With Some Fluffy (But Good) Science

Scientists at the Smithsonian have come up with a new way to figure out the age of ancient silk artifacts, such as flags, clothing and tapestries, using just a bit of fluff that’s fallen off the valuable textiles. The only other scientific way to date silk is by carbon-14 dating, which requires about 100 times more sample than the new technique. (There’s another out-dated “stress-strain measurement” test, which as the name suggests, can put precious silk artifacts through some major mechanical procedures to do the dating. Sounds like just the perfect technique for getting on a textile curator’s black list.) Anyway, the new technique monitors a component of silk called aspartic acid. Silk is essentially a bunch of intertwined proteins extruded from a silk worm, and aspartic acid is found within these proteins. Aspartic acid can exist in two forms, the L- and D- forms, which have the same chemical formula but are mirror images of each other. When a silk worm extrudes the silk protein, the aspartic acid is only in the L-form, but over time it transforms into the D-form. The Smithsonian researchers measured the ratio of the D- and L-forms in a range of silk samples that date back as far as 2500 years ago, when silk was first used as a textile. Older silk samples have more of the D-form, and the scientists have figured out a simple mathematical formula that delivers the age of the silk from the ratio. As an aside, measuring the D- to L- ratio has been helpful for decades in dating a huge range of objects, from ancient ostrich eggs to the bones of human ancestors. And speaking of humans, when doctors take a close look at eye cataracts, low and behold, the aggregates covering the eye lens have a high ratio of D-aspartic acid, which has converted from the L-aspartic acid that is normally found in healthy, young eyes. But back to silk. Although L- to D- dating has been around a long time, the new technique is impressive for the small sample it consumes. Other museums researchers that I contacted for my news story on the topic were enthusiastic about the technique. However they wanted to see the technique validated on more samples, and they wanted the Smithsonian scientists to make sure the L- to D- transformation wasn’t accelerated by environmental exposure–such as a silk suit or tapestry spending years in the sun–which could decrease the accuracy of the...

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