Editing Cologne Cathedral (section)

== Ongoing renovation ==

[[File:Köln, Dom.JPG|thumb|Never without scaffolding: the stones on the cathedral require constant renewal]]

The cathedral is a medieval building that was built very solidly from a structural point of view. At the same time, however, the stone structure requires continuous maintenance and renovation.<ref>Arnold Wolff: ''Die Gefährdung des Domes und die Arbeit der Dombauhütte,'' in: Arnold Wolff, Toni Diederich: ''Das Kölner Dom Lese- und Bilderbuch,'' Köln 1990, p. 73.</ref> The cathedral's master builder [[Barbara Schock-Werner]] said: "Cologne Cathedral without scaffolding is not a pipe dream, but a nightmare. It would mean that we would no longer be able to afford the cathedral."<ref>{{Cite web |title=Köln Reporter-Kölner Dom, die Dombauhütte und die Geschichte des Kölner Wahrzeichens |url=https://www.koelnreporter.de/op-jueck/koelner-dom-dombauhuette.html?K%C3%83%C6%92%C3%82%C2%B6lner=&cHash=80f2652cb86971633e4896fd93a22e54 |access-date=24 October 2024 |website=www.koelnreporter.de |archive-date=29 July 2024 |archive-url=https://web.archive.org/web/20240729194332/https://www.koelnreporter.de/op-jueck/koelner-dom-dombauhuette.html?K%C3%83%C6%92%C3%82%C2%B6lner=&cHash=80f2652cb86971633e4896fd93a22e54 |url-status=live }}</ref>

In fact, the completed cathedral was only visible without scaffolding for a few years. After the official completion of the cathedral in 1880, finishing work continued for around 20 years. Shortly before his death in 1902, master builder Richard Voigtel publicly stated that the cathedral had finally been completed. However, after the wings of an angel figure fell from the façade in 1906, the cathedral master builders resumed the renovation work.<ref>Rüdiger Marco Booz: Kölner Dom, die vollkommene Kathedrale, Petersberg 2022, p. 200f</ref>

The cathedral is built from different types of rock, which weather to varying degrees due to their characteristics.<ref>The materials used were [[trachyte]] and [[latite]] from [[Drachenfels (Siebengebirge)|Drachenfels]], from Stenzelberg, Wolkenburg and [[Wachtberg|Berkum]]; [[sandstone]] from [[Schlaitdorf]], [[Obernkirchen]] and [[Kelheim]], [[limestone]] from Krensheim and [[Savonnières-en-Perthois|Savonnières]] and [[basalt]] from [[Mayen]], [[Mendig|Niedermendig]] and Londorf: Esther von Plehwe-Leisen, Elmar Scheuren, Thomas Schumacher, Arnold Wolff: Steine für den Kölner Dom; Köln 2004</ref> The filigree buttresses and arches are exposed to the weather from all sides<ref>{{Cite web |url=https://www.deutschlandfunkkultur.de/dauerbaustelle-koelner-dom-seit-ueber-100-jahren-keinen-tag.1001.de.html?dram:article_id=365360 |title=Deutschlandfunk Kultur.de: Dauerbaustelle Kölner Dom |access-date=29 July 2024 |archive-date=7 October 2021 |archive-url=https://web.archive.org/web/20211007111334/https://www.deutschlandfunkkultur.de/dauerbaustelle-koelner-dom-seit-ueber-100-jahren-keinen-tag.1001.de.html?dram:article_id=365360 |url-status=live }}</ref>  and are attacked by water, the sulphur content of the air and bird droppings.<ref>Arnold Wolff: ''Die Gefährdung des Domes und die Arbeit der Dombauhütte,'' in: Arnold Wolff, Toni Diederich: ''Das Kölner Dom Lese- und Bilderbuch,'' Köln 1990, p. 82.</ref> Especially from the 1960s onwards, [[acid rain]] severely affected the stones and turned them increasingly black. It was only from the 1990s onwards that air pollution control measures reduced the level of pollution.<ref>[[Deutsche Presse-Agentur|dpa]]: ''[http://www.derwesten.de/kultur/warum-der-koelner-dom-schwarz-bleiben-muss-id10436601.html Warum der Kölner Dom schwarz bleiben muss.] {{Webarchive|url=https://web.archive.org/web/20151226130753/http://www.derwesten.de/kultur/warum-der-koelner-dom-schwarz-bleiben-muss-id10436601.html|date=26 December 2015}}'' In: ''[[DerWesten]].'' 9.&nbsp;March 2015.</ref>

The Schlaitdorf [[sandstone]], which was used from 1842 onwards for the transept façades and the upper parts of the nave and transept, shows the most intensive [[weathering]]. It is therefore constantly being renewed and until the 1980s was preferably replaced with Londorf [[basalt]] lava, which is considered to be very weather-resistant, but is not sandy beige, but grey in color.<ref>Arnold Wolff: ''Die Gefährdung des Domes und die Arbeit der Dombauhütte,'' in: Arnold Wolff, Toni Diederich: ''Das Kölner Dom Lese- und Bilderbuch,'' Köln 1990, p. 80.</ref> Since the 1990s, however, the cathedral master builders have endeavored to carry out the restoration with stones that come as close as possible to the original sandstone.<ref>{{Cite web |url=https://www.koelner-dom.de/fileadmin/media/PDF/newsroom/Geschichte_der_Koelner_Dombauhuette.pdf |title=Koelner Dom.de: Geschichte der Kölner Dombauhütte |access-date=29 July 2024 |archive-date=6 September 2023 |archive-url=https://web.archive.org/web/20230906140036/https://www.koelner-dom.de/fileadmin/media/PDF/newsroom/Geschichte_der_Koelner_Dombauhuette.pdf |url-status=live }}</ref> The cathedral works (Dombauhütte) has already tested numerous means of preserving the stones. A convincing method has not yet been found.<ref>[[Fraunhofer IRB]]: ''Labortechnische Untersuchungen über die Wirkung von Steinschutz- und Konservierungsmitteln auf die Natursteine am Kölner Dom.'' In: baufachinformation.de. https://archive.today/20120719164251/http://www.baufachinformation.de/denkmalpflege.jsp?md=1988023001701</ref> In addition, the iron anchors and dowels that hold the many parts of the architectural decoration are also beginning to rust. They are threatening to crack the stones and need to be replaced with steel parts. "It is therefore foreseeable that no one alive today will ever see the cathedral without scaffolding."<ref>Arnold Wolff: ''Der Dom zu Köln.'' bearbeitet und ergänzt von Barbara Schock-Werner. Köln 2015, p. 10.</ref>

Regular renovation work is required due to sporadic earthquake damage. For example, during the [[1992 Roermond earthquake]], the 400&nbsp;kg finial on the eastern pinnacle of the southern transept gable broke off, smashed through the roof and damaged the roof truss. Four other finials were loosened.<ref>{{Cite web |url=https://www.e-periodica.ch/cntmng?var=true&pid=sbz-003:1992:110::638 |title=e-periodica.ch |access-date=29 July 2024 |archive-date=2 June 2023 |archive-url=https://web.archive.org/web/20230602003802/https://www.e-periodica.ch/cntmng?var=true&pid=sbz-003:1992:110::638 |url-status=live }}</ref>

From May to November 2021, a remote-controlled drone took 200,000 high-resolution photos of all parts of the façade from a distance of five to seven meters and assembled them into a digital 3D model of the cathedral, which offers a very accurate representation with 25 billion polygons. This makes it possible to precisely document the current condition and the need for conservation and restoration, even in remote areas. The 3D model has a size of 50 gigabytes. The cost of creating the model was in the six-figure range.<ref>{{Cite web |date=9 December 2021 |title=5G und Cloud: Amazon und Vodafone vereinbaren Kooperation |url=https://www.faz.net/pro/digitalwirtschaft/5g-und-cloud-amazon-und-vodafone-vereinbaren-kooperation-17676143.html |access-date=24 October 2024 |website=FAZ.NET |language=de}}</ref><ref>{{Cite web |last= |title=Northdocks |url=http://northdocks.com/neues-und-in-den-medien/drohne-inspiziert-den-dom/ |access-date=24 October 2024 |website=northdocks.com |language=de-DE |archive-date=4 March 2024 |archive-url=https://web.archive.org/web/20240304181053/http://northdocks.com/neues-und-in-den-medien/drohne-inspiziert-den-dom/ |url-status=live }}</ref>