Padrão dos Descobrimentos - Lisbon, Portugal

Kärcher cleans the Monument to the Discoveries

In addition to the Brandenburg Gate, Kärcher cleaned a second building of historical importance in the summer of 1990: the Padrão dos Descobrimentos ("Monument to the Discoveries").

The monument, which stands at the entrance to the port of Lisbon, was built in 1960 in honour of the Portuguese explorers. Its interior houses a maritime museum and a viewing platform, accessible by a lift. The 65-metre-high building depicts a stylised sailing ship carrying the heroes of Portuguese seafaring.

The monument is constructed from brick and faced with limestone tiles. This limestone showed two types of dirt: one consisting of dark-coloured organic deposits like lichen, moss and dirt, and the other a white gypsum efflorescence. This is likely to have formed as a result of a chemical reaction between the limestone and the sulphur dioxide in the air.

It became clear after several tests that it would not be possible to remove the dirt using a high-pressure cleaner (150 bar/ 1,000 litres of water). Even chemicals made no difference: acidic cleaning agents cannot generally be used on limestone, and alkaline cleaning agents did not achieve satisfactory results.

Only the Facade Clean Trailer was successful in removing every inch of the dirt. This machine uses an air stream to which spray agent can be added in a precisely regulated dose. Adding water at the spray nozzle prevents the development of dust. The technical equipment consists of a compressor and water pump, both of which are driven by a diesel engine. The machine also features a blasting device with pressure chamber. All of the engines are stored compactly on a vehicle trailer.

Removing the dirt in two stages with a break of one to two hours between procedures proved to be most effective for this monument, rather than cleaning in one procedure. After a cleaning period of around four weeks and a final impregnation of the monument's 6,000 m² surface with Kärcher's RM 441 stone impregnator, a ceremony was held to open the monument to the public.

For Kärcher, this project further confirmed its expertise, especially in challenging cleaning tasks.