European Day of Restoration: Protecting Cologne's cathedral

Since 2018, the European umbrella organization of restorers' associations has been organizing the European Restoration Day.

This year it falls on October 16 and in Germany the motto is "Cultural Heritage in Climate Change" and is focussed on restorers' efforts towards environmental protection.

With 200 events held around Germany, restorers provide an insight into work that is typically done behind closed doors, whether in museums, private studios, universities, churches or even castles. "We want to make people aware of the importance of cultural heritage and the key role of restorers in the preservation of cultural assets," the association says on its website.

One restoration focal point is Cologne's main landmark: the Cologne cathedral.

As one humorous saying in the city goes: "When the Cologne cathedral is finished, the world ends."

This refers to the fact that the church is nearly always seen bedecked with scaffolding. "That's a good thing," says cathedral master builder Peter Füssenich, "because if the cathedral were scaffolding-free, it would mean that the structure had fallen into disrepair."

Cologne Cathedral attracts millions of visitors

The Cologne Cathedral Builders' Works (Kölner Dombauhütte), the cathedral's construction team, is the organization tasked with preserving the Gothic cathedral for posterity.

After all, the cathedral has been standing for 700 years. It defied the Thirty Years' War between 1618 and 1648, and was considered a national symbol of Germany when it was completed in the 19th century.

Miraculously, it managed to stay standing despite bombing during World War II and was hailed as a symbol of postwar reconstruction.

Today, the famous structure, which was designated a UNESCO World Heritage Site in 1996, attracts up to 7 million visitors a year.

What often does not get attention is the team of people working for the Cathedral Builders' Works, who are responsible for the cathedral's construction and maintenance. Restoration is a backbreaking job that requires a great deal of knowledge and even more craftsmanship.

In the 19th century, when the medieval cathedral was nearing official completion, the team of builders grew to 500 people.

In 1902, the cathedral's then master builder, Richard Voigtel, announced that the cathedral construction was complete. However, when a statue of an angel fell from the facade only four years later, construction work quickly resumed.

Today, the Cologne Cathedral Builders' Works has 100 employees. It includes specialists in every trade, whether in stone, glass, metal or woodworking.

'Nothing more grandiose than this building'

Tanja Pinkale, head of the stone restoration workshop, is one of them. The trained stonemason and restorer has dedicated herself to working on the Cologne cathedral and says her work is part scientific, part craftsmanship. Half of her time, the 32-year-old pores over plans and figures in the office. But as often as she can, she gets up on the scaffolding "at the stone," as the stonemasons say.

"There is nothing more grandiose than this building!" says Pinkale.

The Gothic cathedral with its twin towers rises above the metropolis. Rung by rung, Pinkale climbs the towering scaffolding made of poles and ladders.

The north side of the cathedral, where the choir chapel faces Cologne's central train station, is currently the cathedral's largest construction site. This is because the trachyte masonry from the 13th century has begun to crumble.

To be repaired, it must first be carefully sandblasted to preserve as much of the surface as possible. "We're doing it as gently as possible," the restorer promises.

Accompanying her on the wind-swept platform at a height of 15 meters (49 feet), is deputy master builder, Albert Distelrath, who manages the construction site. With a connoisseur's eye, he examines the crystal inclusions that are so typical of trachyte.

In the Middle Ages, the volcanic rock was shipped to Cologne from the Drachenfels near Bonn, where the Cathedral Builders' Works had its own quarry. The location of Cologne cathedral and other sacred buildings along the Rhine River is no coincidence.

Staying true to the original

"Trachyte is good," says Distelrath, "but unfortunately also very inhomogeneous." If the temperature fluctuates, this leads to tension and cracks. Salt and frost penetrate. Parts of the stone chip off.

Around 50 types of stone have been used in Cologne cathedral over the years. Almost all walls and pillars are made of trachyte. The builders used columnar basalt and tuff for the foundations, and tuff for the vaults.

"We try to reconstruct all elements of the cathedral as true to the original as possible, down to the last detail," says Pinkale. The surviving workpieces from the Middle Ages and the 19th century serve as models.

Stone for restoration works, with the right color, structure, water absorption and drying properties, is now obtained from a quarry in the Italian town of Montemerlo near Padua. Surfaces are smoothed and joints filled with a specially developed mortar.

Climate change is damaging the cathedral

But the deterioration of the stone is not the only threat to the cathedral.

For a long time, it was also damaged by the sulphur in the air that clogged the walls and turned them black. That has changed. "The air is cleaner now," says the stone restorer, "but the greenery grows faster." Moss, grass, small trees — the vegetation turns the cathedral into a large biotope.

But in fact, climate change is the main concern for the restorers. "Heavy rain, storms, drought — the cathedral wasn't built for such a climate!" says Pinkale. Their work here is a race against time. 

A climate station now monitors the wind and weather around the cathedral. The data is followed by researchers, and if the winds are too strong, the police close the cathedral square.

It will take a good 15 years for the trachyte masonry, the oldest part of the cathedral wall from the 13th century, to be cleaned and restored. "Actually, I already know which projects I will be working on in the next 40 years," laughs Pinkale as she carefully climbs down the scaffolding again. 

This article was originally published in German.