Scientific sleuths

From manuscripts to walrus tusks, Yale’s heritage scientists probe artifacts with x-rays and lasers, uncovering secrets hidden in pigments, pages, and silver.

Paintings, fossils, silver, manuscripts, porcelain and earthenware fuel curiosity for those who work in the heritage science field, where the technical analysis of cultural artifacts and natural history specimens are a match made in heaven. The tools that support this union are many, but foremost among them are x-ray fluorescence (XRF) instruments, large and small, whose electromagnetic waves, generated in an x-ray tube, help reveal the elements that an object is composed of.

Delving into the material depths of art and artifacts in Yale’s Heritage Science Research Lab at the Institute for the Preservation of Cultural Heritage (IPCH) are three staff members: Anikó Bezur, Wallace S. Wilson Director of Scientific Research, Richard Hark, senior heritage scientist, and Rachel Heyse, laboratory assistant, who supports Bezur and Hark’s research by keeping the tools and lab spaces in peak working order.

The trio exercises their exacting knowledge most often in collaboration with Yale’s museums and libraries. Such requests entail studying objects for exhibitions or to support their conservation, and asking questions like: What are they made of? Are they consistent with what we know about historical techniques? Can we identify the pigments originally applied?

Sometimes their expertise is requested by a professor developing a course for Yale students. Ayesha Ramachandran, professor of comparative literature, reached out early last year when she was envisioning a syllabus for what has become a spring 2026 course, “Technologies of the Book,” which Bezur and Hark co-teach with her.

“Our favorite tool”

The large non-descript white room off the main area of the IPCH Shared Conservation Lab is completely lead-lined for safety and contains a behemoth x-ray instrument. Secured under the Bruker M6 Jetstream scanning x-ray fluorescence spectrometer is a 16th-century Spanish Cistercian epistolary manuscript (religious text in letter form). Open to a page rich with pigments, this illuminated manuscript is what Bezur calls “the marquee object” they are focusing on for Ramachandran’s course.

“This favorite tool of ours can take millions of analysis points without damaging the object,” said Bezur. “The frame allows the x-ray tube and the side detectors to move back and forth over the manuscript to see what elements are present and where. Computer-generated maps show us, in this case, the distribution of iron, which is a component of a wide range of pigments routinely used by artists over the centuries.”

The iron appears orange on the computer screen connected to the instrument and Hark notes that it is under the gold and part of the script in this page of the manuscript. The iron-rich material, called bole, is a fine red clay mixed with glue and spread as a base layer under gold leaf, so it sticks smoothly and gives off a warm, rich glow. The ink is iron gall ink, a traditional ink made from oak galls. It is rich in tannins, iron sulfate (known historically as green vitriol), and gum Arabic binder made from acacia tree sap.

“Using this technology is like reverse engineering what something is made of,” said Hark. “That can answer questions about many things, but in the case of this manuscript, we’re trying to better understand the working methods of the infamous Spanish Forger, who faked miniature medieval scenes in illuminated manuscripts in the nineteenth and twentieth centuries.”

“We know the Forger used the traditional red bole technique for applying gold,” said Hark. “So, it doesn’t tell us as much as the presence of chrome yellow and Prussian blue would. These are pigments mixed to create the green color in most of the miniatures, indicating that the miniatures must have been produced after the early nineteenth century, which is when chrome yellow became available to artists.”

Small but mighty

Handheld tools, specifically x-ray fluorescence and laser-induced breakdown fluorescence spectrometers, are housed in another lab space that contains smaller instruments. These can travel to museums and libraries on campus as well as to off-campus sites as part of collaborative projects, including recent ones in Barbados and South Africa.

Like the large version, the handheld X-Ray Fluorescence (XRF) spectrometer detects the elements in an object. It provides data on the object in one location at a time and analyzes a larger area of the location’s surface when it does so. The spectrometer played an important part in the technical analysis of works at the Barbados Museum and Historical Society that will be compared with similar analyses of paintings depicting the island of Barbados at the Yale Center for British Art and in the collection of the U.K.’s National Trust.

Hark demonstrates the laser-induced breakdown spectrometer (LIBS) by holding it in one hand while his other hand presses a silver cup to the front of the instrument where a laser pulse rapidly determines the chemical make-up of the sterling silver object. Each time the laser fires, it creates a small plasma plume that emits light the sensor can “read,” digging a little deeper into the surface of the object, so a minuscule amount of material is removed. This minimally invasive sampling is used only when scientists cannot obtain the information any other way.

Science meets art

Bezur has been conducting this research at Yale for over 13 years, after working at Chicago and Houston museums. Born in Budapest, Hungary, she learned English in Scotland while her father was on a research assignment. She finished her senior year of high school at Choate Rosemary Hall and attended Brandeis University on a scholarship to study chemistry.

“While I was at Brandeis, I found that I really liked art history along with chemistry, and that’s where I learned about the field of heritage science,” said Bezur. “When I first joined Yale, I helped design and build labs with instrumentation and set up a research program in heritage science.”

Hark also began his career in chemistry. “I was a chemistry professor for 24 years, and during that time I became involved in cultural heritage work,” said Hark. “This included a sabbatical year in the U.K. working at University College London and the Victoria and Albert Museum. Then I came to Yale on a sabbatical leave and never left.”

“Reverse engineer this building”

Heyse has learned all of the components of the workspaces in the Heritage Science Lab and IPCH that keep the labs and the machines up and running. She works closely with the Yale West Campus facilities team to monitor the temperature and humidity of the rooms so that the art, artifacts, and instruments are not compromised in any way. She is also participating in a project to make the on-site collection storage more environmentally friendly.

Handy as the day is long, Heyse has been taking things apart and putting them back together since her childhood days playing in the workshops of her grandfather and father, both carpenters. She has a toolbox on the premises to show for it.

One recent repair stands out for its success after hours of patience and persistence. The machine in need of repair creates suction across its surface to treat paper objects with cleaning solvents, a process that helps prevent stains from spreading and allows the paper to remain flat as it dries.

When the machine began having suction issues, Heyse had to send it to the manufacturer’s facility for further diagnosis. She disassembled it with the help of art handlers, and after an in-depth diagnostic analysis identified the issue, the component was fixed. When the machine was up to the required specifications, a huge bow was attached for all to admire.

“One of the special things that Rachel does here is to basically reverse engineer this building,” said Bezur. “She’s learned so much and has been very tenacious about understanding what’s going on here. It’s been incredibly helpful to have someone who really pays attention and is creative in how she problem-solves.”