Cologne Cathedral is one of the most iconic and well-visited buildings in Germany, attracting around 6 million visitors per year. The cathedral's sandstone exterior is often perceived as dirty, and this is due to the way that the sandstone reacts with the sulphuric acid in the rain, turning dark grey over time. The cathedral is constantly being cleaned, but the process is lengthy and expensive.
Characteristics | Values |
---|---|
Reason for dirtiness | The sandstone used in the construction of the cathedral reacts with the sulphuric acid in the rain, turning the stone dark grey over time. |
Maintenance | Workers clean the façade almost constantly. |
What You'll Learn
The type of stone used to build the cathedral
The Cologne Cathedral is constructed from a variety of stones, including sandstones, carbonates, and volcanic rocks. The original building stone, Drachenfels trachyte, is a light grey, porous, porphyritic trachyte with phenocrysts of sanidine. Trachyte is a type of igneous volcanic rock. The Drachenfels trachyte was sourced from quarries in the Siebengebirge, near Cologne, and was used for the medieval sections of the cathedral. However, by the time construction resumed in the 19th century, the Drachenfels quarries were no longer operational, so alternative stones were used.
In the 19th century, the first replacement stone used was local latite from the Siebengebirge, followed by sandstone from Schlaitdorf in southern Germany. When a railway was built between Cologne and Minden, "Obernkirchner" sandstone from Lower Saxony was used, as it could be easily transported. In the 20th century, "Krensheimer Muschelkalk", a limestone consisting of shell fragments, was used, followed by decay-resistant basalt lava from "Londorf". Presently, the cathedral is using trachyte from "Montemerlo" in Italy to replace the deteriorated Drachenfels trachyte, and sandstone from "Bozanov" in the Czech Republic to replace the Schlaitdorfer sandstone.
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The effects of acid rain
One of the most visible effects of acid rain is the damage it causes to buildings, monuments, and statues. The Cologne Cathedral, for example, has turned dark grey due to the reaction of sulphuric acid in the rain with the sandstone used in its construction. This process of discolouration is a common effect of acid rain, affecting other monuments and buildings around the world, including London's Westminster Abbey, the Colosseum in Rome, and India's Taj Mahal.
Acid rain also causes corrosion and deterioration of various materials, including marble, brick, limestone, and certain metals. The corrosion of marble and brick surfaces leads to the pitting and canyoning of buildings, monuments, and statues, causing severe damage over time. Additionally, metals such as bronze, nickel, zinc, copper, and carbon steel are susceptible to corrosion from acid rain, as evidenced by the streaks and discolouration on bridges and other metal structures.
The impact of acid rain extends beyond man-made structures. It also affects plant life, wildlife, and aquatic ecosystems. Acid rain can irreparably harm soil and trees by disturbing their pH levels, making them more vulnerable to naturally occurring chemical threats and hindering their ability to recover from injuries and damage. Additionally, acid rain contributes to the slow death of plants and trees due to nutrient starvation and oxygen deprivation, ultimately disrupting the natural balance of the ecosystem.
To mitigate the effects of acid rain, it is crucial to reduce emissions of sulphur dioxide (SO2) and nitrogen oxide (NOx), the chemical precursors of nitric and sulphuric acids. This can be achieved by transitioning from fossil fuels to green energy sources such as wind and solar power. By addressing the root causes of acid rain, we can help preserve our environment, infrastructure, and historical landmarks for future generations.
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The cathedral's proximity to the train station
The Cologne Cathedral is conveniently located right next to the main train station, making it easily accessible to visitors. However, its proximity to the train station has also contributed to the accumulation of dirt and grime on the cathedral's exterior.
The train station's presence near the cathedral has had a noticeable impact on its cleanliness. One visitor commented on the hundreds of years of filth that seemed to cover the cathedral, possibly due to the soot and pollution from passing trains. The steps leading to the cathedral were particularly mentioned as being dirty and in need of a clean.
The train station's proximity also extends to the overall impression of the area. The combination of a dirty railway station and the unkempt surroundings, including beat-up old stores and graffiti, can detract from the initial beauty of the cathedral.
Despite the negative impact of the train station's proximity, the Cologne Cathedral remains a popular destination for tourists and visitors. Its impressive size and architecture, as well as its historical significance, make it a must-see attraction. Visitors can easily access the cathedral during a short layover or train transfer, contributing to the high number of annual visitors.
While the train station's presence has contributed to the dirtiness of the Cologne Cathedral, it is also a testament to the cathedral's resilience and longevity. The cathedral has endured for centuries, withstanding the effects of pollution and the passage of time, to remain a majestic and awe-inspiring landmark in the heart of Cologne.
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The building's age
The Cologne Cathedral is a UNESCO World Heritage Site and has been a tourist hotspot for 800 years. Construction of the cathedral began in 1248 and was completed in 1880, taking over 600 years to finish. The cathedral was built to house the Shrine of the Three Kings, which holds the bones of the Three Wise Men from the Bible. The cathedral is the tallest twin-spired church in the world, the second-tallest church in Europe, and the third-tallest church globally.
The cathedral's long construction period is partly due to the fact that most of it was built before electricity or steam power, so all the massive stones had to be lifted, carved, and affixed using simple tools. Additionally, church-building is expensive, and there were periods when the project was halted due to a lack of funding.
The cathedral's dark colour is not due to a lack of maintenance but because it is made of porous sandstone, a soft rock that absorbs air impurities easily. The sandstone reacts with the sulphuric acid in polluted rain, turning dark grey over time. This is why repaired sections look much lighter than the rest of the building, but they, too, will darken to match the older stone over time.
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The effects of World War II
Cologne Cathedral was hit by 14 bombs during World War II. The building did not collapse and remained standing in an otherwise flattened city. The cathedral's twin spires were an easily recognisable landmark for Allied aircraft bombing. Badly damaged, the cathedral nevertheless stood strong. Repairs to the damaged parts were finally finished in 1956, though some sections were deliberately left unprepared as a memorial to what had happened.
The cathedral's stonework was also affected by the war. The sandstone used in its construction reacts with the sulphuric acid in the rain, turning dark grey. This is why repaired sections look much whiter and lighter than the rest of the building, although in time they will darken to match the older stone. The cathedral's workers are constantly cleaning the façade, but it is a never-ending task.
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Frequently asked questions
The sandstone used to build the cathedral reacts with the sulphuric acid in the rain, turning it dark grey over time.
No, but the cleaning process is lengthy. By the time the workers finish cleaning the facade and start over, the first parts need cleaning again.
No, the interior is also affected by the dirt from the outside.
No, the cathedral was not always so dark grey. The sandstone gradually reacts with the sulphuric acid in the rain, changing its colour over time.
The cathedral is constantly being renovated and repaired. However, the sandstone used to build the cathedral is porous and susceptible to air impurities, making it challenging to preserve.