While the prospect of warmer Arctic temperatures generally earns negative reviews from many people, one group of researchers has been welcoming a positive aspect of climate change. Retreating ice fields are exposing archaeological treasure, items that people moving through these areas left behind thousands of years ago.
Kate Helwig, senior conservation scientist at the Canadian Conservation Institute, samples pigments from a painting. Photo credit: © Government of Canada, Canadian Conservation Institute, CCI 99587-0035
Retrieving these objects can be a challenge, one that calls for helicopter travel and sometimes dangerous climbing across unstable mountain slopes in remote parts of the Canadian north. Nevertheless, the risk is more than justified. Because these artifacts have been frozen, they also contain preserved samples of organic compounds that were part of their original make-up. If researchers can get to these agents before weathering processes break them down, subsequent analysis could shed entirely new light on how some of North America’s first inhabitants made use of local sources to make clothing or tools. “It’s like time has been frozen,” says Kate Helwig, an Ottawa-based senior conservation scientist who has been working with her counterparts in the Yukon on a variety of hunting weapons that have been recovered in this way. “They’re just amazing objects.”
Helwig offers the example of a carved antler point that is delicately balanced and crafted with fine slots where razor sharp stone chips would be inserted for a deadly impact. This item was likely part of a throwing dart, a projectile where the speed and power was enhanced with a hand-held throwing mount. The point appears to have been personalized with an enigmatic symbol that may be a “maker’s mark.”
A “maker’s mark” left by the unknown person who crafted this Arctic hunting dart thousands of years ago, which was analyzed at the Canadian Conservation Institute in Ottawa. Photo credit: © Government of Canada, Canadian Conservation Institute, CCI 95190-0003
As a chemist, Helwig is particularly struck by the adhesives used to assemble these devices. In a recent study of more than a dozen examples of throwing darts and arrows taken from ice patches in the Yukon and Northwest Territories, the key ingredient was found to be spruce resin, which served as a very effective means of binding these hard-working parts together. “In a few cases, the spruce resin was mixed with red ochre to produce a compound adhesive,” she says. “The use of an adhesive modified with ochre like this is a first in North America. However, there’s very little known about this technology because there aren’t many well-preserved objects that remain.”
This fresh insight into the design of an ancient tool followed a comprehensive analysis that included Fourier transform infrared spectroscopy, gas chromatography-mass spectroscopy, Raman spectroscopy, scanning electron microscopy energy dispersive spectrometry and polarized light microscopy. Few places in Canada would be prepared to fill this tall scientific order for an archaeological specimen. Helwig, however, works for the Canadian Conservation Institute (CCI), a fully outfitted hub of laboratories that specialize in just this kind of activity.
Located in Ottawa’s east end, CCI was established in 1972, just after Canada signed on to a United Nations initiative to oversee the protection and preservation of cultural properties around the world. Such properties could be anything from artwork harboured in a country’s museums or galleries to physical remnants of the past, such as remains uncovered through archaeological investigation. As a special operating agency of the federal Department of Canadian Heritage, CCI is the primary facility where those responsible for these properties in Canada can turn for help.
Senior conservation scientist Kate Helwig carries out non-invasive Raman spectroscopy of a painting at the Canadian Conservation Institute. Photo credit: © Government of Canada, Canadian Conservation Institute, CCI 120966-0007
In some cases, that means tackling crises of one sort or another. For example, curators responsible for a valuable painting may discover to their horror that small craters are opening up on its surface or that liquid is suddenly oozing out of cracks in what appeared to be dried paint. Some of these chemical breakdowns have become a well-understood part of art history but others are outright mysteries that regularly arrive on CCI’s doorstep demanding a solution. “I was amazed that such a place existed,” says Marie-Claude Corbeil, who was hired there 27 years ago while she was looking for work after completing her doctorate in chemistry. She admits to having no idea that her skill set could be applied in this way “and I just fell in love with it.”
Corbeil now manages CCI’s conservation science division, which oversees a wide range of challenges in identifying the problems that can beset cherished works of art that people are often desperate to save. Her area of expertise lies with the pigments used in classical and contemporary painting, which can undergo unexpected reactions after just a few decades on display. One of her favourite examples has been the emergence of compounds of long-chain fatty acids and metals that form when hydrolysis releases those acids from drying oils and they react with paint pigments. They have a soapy, waxy texture that can remain harmless to a painting unless they agglomerate to form large protuberances that could subsequently break through the paint, leaving the artwork with what looks like a bad case of acne.
Art conservation specialists have a long tradition of characterizing reactions and mitigating damage in the work of classical artists such as Leonardo or Rembrandt. However, far less is known about some of the newer pigments and materials that emerged from the industrial era. Corbeil’s team has been among the pioneers attempting to collect and classify the behaviour of these chemicals.
Canadian Conservation Institute scientist Season Tse has been among the world’s leading developers of microfading, a technique for predicting how inks and colorants on various papers and textiles will change over the course of years or decades. Photo credit: © Government of Canada, Canadian Conservation Institute, CCI 122884-0140
While traditional artistic materials may be difficult to preserve and protect, she says, things are worse with modern products, especially mass produced consumer goods. These artifacts have become essential to documenting historical lifestyles but they were never intended to have a long shelf life. Many of these goods were created with emerging generations of 20th-century polymers, which have been found to undergo all manner of unexpected transformations over time, depending on how and where they were stored. “For us as scientists, you think you know everything,” she says. “Then along comes a degraded plastic object that oozes a gooey substance and people want to know what’s happening to their object and what they should do with it.”
Repeated attempts to answer those questions in recent decades have turned art conservation from a cloistered, almost secretive pursuit into a field that now operates on a secure scientific footing. “It’s a more rigorous approach,” Corbeil says, “based on analysis, testing and research to develop new treatments and new products.”
Helwig agrees, adding that the resources available at CCI make for a unique combination of pure chemical research and practical applications. She started there 23 years ago after obtaining a master’s degree in chemistry and then switching to the art conservation program at Queen’s University. “I found that it’s a really wonderful way of combining an interest in art with chemistry,” she says, adding that the sheer variety and unexpected nature of the work is constantly stimulating. “Yesterday I was working on a 17th-century Quebec painting and then I went on to a very odd sculptural work from the 1980s that had white material dripping from one of its components. You never know what you might find and that makes it fun.”
CCI is also home to significant innovations like microfade testing. This method addresses the particular challenges of identifying objects that are very sensitive to light. Those challenges will be familiar to anyone who has watched a prized family photograph lose colour and even its resolution as it hangs on a brightly lit wall. For just this reason, many artifacts are displayed to the public in dimly lit settings, which can be annoying to observers but represents an attempt to keep light from compromising the works.
In the 1990s, an American conservation scientist developed a technique for anticipating the effect of light. It uses a highly focused beam of very bright light and a spectrophotometer, measuring and recording the colour while microscopically fading the test surface. Starting with a powerful source such as a xenon arc lamp, light is filtered and focused onto a spot as small as a third of a millimetre in diameter. The intensity of the light spot is about 50 to 70 times that of the noonday sun. In this way, the effect of years of exposure could be assessed in a matter of minutes yet leave no noticeable trace on the artifact. “There was really no way of determining the sensitivity of material to light,” says Season Tse, a senior conservation scientist at CCI who has become the country’s leading expert on microfade testing. “Depending on the substrate, depending on the history of the piece, depending on the matrix of the material, the fading properties could be very different, Tse says. “Prior to this technique, people were always guessing.”
Tse was introduced to microfading a decade ago, when she was presented with the first Maple Leaf flag to fly on Parliament Hill in the 1960s. Those responsible for displaying it in various venues across the country were worried about how well it would hold up to repeated exhibitions. When Tse learned that the only available microfade testing service was in the United States, she used this request as an impetus for CCI to build one of its own. Since then she has refined the technique, developing a portable system that could be taken on the road rather than having to bring objects to CCI. She has also been the first to use results from microfade testing with the CCI online Light Damage Calculator, which enables museums to get a visual estimate of how various materials may change with different lighting scenarios.
Tse has applied microfade testing to documents such as the two original copies of the 1982 Proclamation of the Constitution Act, 19th-century scrapbooks with herbarium sheets compiled by the celebrated Ontario settler Catherine Parr Traill and herbarium sheets from one of the Sir John Franklin expeditions. In some cases, the results have determined that these objects will hold up well to brighter light, allowing them to be displayed under higher illumination, something that is bound to please anyone tired of squinting at artifacts presented in gloomy rooms.
Such results also sit well with the staff at CCI, who find themselves in the business of ensuring that art — in whatever chemical form it might take — remains as accessible as possible to the Canadian public. Corbeil concludes that fulfilling this mandate makes every project a new adventure, even if the underlying science remains familiar. “You may find the same pigment over and over again,” she says, “but the painting that you find it in is unique.”