At Notre Dame Cathedral, a Hidden History Revealed

Art historian Caroline Bruzelius studied cathedral during its restoration

Caroline Bruzelius during restoration of Notre Dame Cathedral in Paris.
During the restoration of Notre Dame, Caroline Bruzelius was part of a research team studying the cathedral’s centuries-old stone and mortar.

As a young Duke art history professor in 1979, Caroline Bruzelius convinced officials at Notre Dame Cathedral in Paris to let her climb scaffolding during a renovation to get a close look at the architecture.

It was, she thought, a once-in-a-lifetime opportunity. She’d return many times over the next seven years until the work was completed in 1986.

Decades passed – her work on Paris Cathedral was published in 1987, and she moved on to other projects.  Then in 2019, Notre Dame suffered a devastating fire. The cathedral was shut down and a five-year restoration began.

Because of her earlier work and the article on Notre-Dame, published in 1987, Bruzelius, by then retired from Duke, was invited to join a research group examining stone and mortar during the restoration. Suddenly, she had a twice-in-a-lifetime chance to study the 13th century cathedral’s design and architecture in fine detail.

But this time, a twist: Because restorers were giving the cathedral’s Parisian limestone a thorough cleaning, she was able to study the walls free of eight centuries of dirt, grime and soot.

“As a result of a new cleaning technique, a latex spray and peel, which cleaned the thousands of fossil indentations in the limestone, we could see things as never before. For the first time in decades, the original surfaces of the upper walls were clean and brightly lit, a wonderful opportunity for scholars,” said Bruzelius, an internationally regarded scholar of medieval architecture.

“Parisian limestone is very porous. It’s full of cavities that had collected 850 years of dirt, which was finally removed.  The cathedral now looks as bright and fresh as when it first opened in the 13th century. Every few centuries you need to take a bath!”

Bruzelius made several research trips beginning in 2021, each time donning a hazardous materials suit that was required as protection from the toxic dust from the destruction of the lead roof in the fire.

“The cathedral now looks as bright and fresh as when it first opened in the 13th century. Every few centuries you need to take a bath!”

Caroline Bruzelius

It was a change from her last 1986 visit, when she had to bring her infant son, Anders, along, toting him 108 feet up the scaffolding, strapped tight in a baby carrier. She would spend 37 years at Duke teaching various art history courses including her popular Gothic Cathedrals class, in which students would design their own cathedral using Notre Dame and others as guides.

Caroline Bruzelius and others climbed up high in the Notre Dame rafters for their research.
Caroline Bruzelius and others climbed up high in the Notre Dame rafters for their research.

Bruzelius retired from Duke in 2017 and now lives in Massachusetts, where she has been, she admits, a “complete failure as a retiree.” She continues to pursue a series of ongoing research projects, and Notre Dame is seldom far from her mind.

The cathedral reopened to much fanfare earlier this month, and Bruzelius says the data from all the specialized research teams (wood, metal, glass, decoration, etc.) will eventually be available in a public, shareable database. The research led her and others to some valuable finds.

Of note:

  • Researchers in the “metals group” discovered that iron clamps going from stone to stone created a kind of reinforcing belt running the circumference of the walls.  This innovative use of metal was adapted inside the building to lighten the structure and attach shafts. While metal had been identified around the top walls in the 19th century, researchers hadn’t understood until now how thoroughly iron was integrated into the design and construction of the building.

“The metal means they could use less stone as they progressed through the building,” Bruzelius said, “this made the cathedral lighter and more efficient: less stone to quarry, transport, carve and lift. The visitor at ground level can’t see the metal clamps, which are embedded in the structure, but when you are working from the scaffolding, and can get your nose within two inches of the wall, you understand their fundamental role in holding the parts together. It’s an internal, hidden support system.”

  • Who built Notre Dame? There are very few documents on the construction of the cathedral, but the “stone and mortar” research team was able to examine surfaces closely enough to document the mason’s marks – basically a signature each stone worker would leave as evidence of his work.
  • Innovation over time. The cathedral took a century to complete, and researchers now can see evidence of how building methods and technology changed in that time, Bruzelius said.

“The cathedral was built over the course of more than 100 years and reflects a lot of experimentation and structural innovation,” Bruzelius said. “Lifting devices got better, they started using different types of chisels, so stone cutting became more efficient. The building is full of change and experimentation. When you walk inside, the cathedral looks totally unified, but up high and close to the walls, you see that the masons were constantly introducing new ideas.”