Cleaning of Bismarck Monument in Hamburg, Germany
In the middle of the Elbe metropolis of Hamburg, between Landungsbrücken, St. Pauli and Michel stands the world's largest Bismarck statue. Kärcher cleaned the 113 feet high and over 100 year old monument over a period of almost two months.
In the middle of Hamburg, between Landungsbrücken, St. Pauli and Michel stands the world's largest Bismarck statue, which is currently being cleaned by Kärcher. The granite surface of the 113 feet high and over 100 year old monument is heavily soiled by biological growth such as algae, lichens and moss and by graffiti. The work will take a total of two months, during which Kärcher's experts will clean the enclosure wall, the pedestal and the statue itself of any contamination.
In order to determine the optimum process, Kärcher experts carried out various tests and created sample areas in advance. "The chosen procedure without chemicals removes the impurities in a gentle way," explains Nick Heyden, who as project manager of Alfred Kärcher SE & Co. KG, is responsible for the on-site implementation. "We are proud to be able to make a contribution to the preservation of the monument with our material-conserving cleaning technology."
The Kärcher experts use three different cleaning techniques. First, larger plants on the surface are removed by hand before dust, bird droppings and other biogenic vegetation are removed with the help of a hot water pressure washer. The 176 to 194 degree hot water hits the surface at a pressure of 1 to 2 bar - a particularly gentle method for granite stone. The five cleaning experts then use a low-pressure particle blasting process with the blasting agent aluminium silicate (grain size 40-180 μm) to remove graffiti and lime deposits. Finally, the entire monument is vacuumed with commercial wet/dry vacuum cleaners, and at the end the last remaining dirt is rinsed off again.
The cleaning was often done in the early morning hours.
The approximately 176-194° F hot water hit the surface with a pressure of 1 to 2 bar - a particularly gentle method for granite stone.
Statue in tilted position
The cleaning of the monument, built between 1901 and 1906 in honor of the first Reich Chancellor Otto von Bismarck, is preceded by a comprehensive renovation, which is currently still in the planning stage. In order to use the 62-foot high base as an air-raid shelter, the foundation was filled with 2,200 tons of concrete during the Second World War - too much for the statics of the building. The monument was tilted and cracks appeared in the surface. One advantage of cleaning is that after removing the dirt, a precise inventory of the damage can be made.
Facts at a glance
Soiling: Dust, bird droppings, biogenic growth, lime, graffiti
Cleaning technique: Hot water pressure washer without chemical additives with 1-2 bar and 176-194 degrees water temperature, low-pressure micro particle blasting with fine aluminium silicate (40-180 μm) as abrasive
Execution: March-April 2020