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Humboldt Forum

Used as the Humboldt Forum, the Stadtschloss Berlin houses modern exhibition rooms behind baroque facades that were created as a precise reconstruction. For the coloured sections, the planners relied on KEIM products. But how do you determine the historical colouring of a building whose last remains were blown up 70 years ago?

Architect:
Franco Stella Berliner Schloss-Humboldtforum-Projektgemeinschaft
Photos:
KEIM / Stephan Falk
Products:
  • Soldalit
  • Soldalit-Fixativ
  • Restauro-Lasur
  • Restauro-Fixativ
  • Optil

Baroque shell, modern core

With the reconstruction of the Berlin Palace, a piece of urban repair in the heart of Berlin is now complete. The palace was the starting point for the city's most famous architectural ensemble: the armoury, the cathedral, the Neue Wache, Humboldt University, Museum Island - they all related to the palace. And of all things, this original building block had been missing since it was blown up in 1950 after severe war damage. The reconstruction now closes the urban gap. Consequently, the reconstruction of the historical appearance is limited to the facades, while the interior completely meets today's requirements of a modern exhibition and event centre.

Searching for the right colour shade

But what colour should the reconstructed plaster facades be? Original building fabric was just as non-existent as the original building documents. So which sources should be consulted instead? Early pictorial representations were etchings made by Johann David Schleuen around 1750, but they were not coloured. It was not until paintings by the Biedermeier artist Eduard GΓ€rtner from the beginning of the 19th century that coloured depictions of a yellowish castle can be found, but by this time the building was already over 100 years old. A comparative reconstruction also proved difficult: the facades of the rococo Sanssouci Palace in Potsdam, for example, are yellow, while the baroque armoury opposite the Berlin Palace, for example, is painted pink. Finally, a preserved piece of plaster was found that had been stored in Charlottenburg Palace. This original find, about the size of a hand, shows a quince-like yellow hue and could be dated to 1820 by a restorer's expert opinion. According to today's knowledge, this is the earliest confirmed colouring, so that this tone was chosen. It also harmonises with the sandstone of the columns, cornices, window jambs and balustrades.

Dedicated to the original

A great deal was done in the painting process to achieve a look that was as close as possible to a historical appearance. Instead of the emulsion paints commonly used today, mineral products from KEIM were used. KEIM Soldalit was first applied to the lime-cement plaster as a base colour. To ensure that this layer did not appear too opaque but slightly cloudy, the painters thinned the paint by 50 % with KEIM Soldalit-Fixativ. In order to achieve a depth effect at the same time, KEIM Restauro-Lasur was then applied in two work steps, also diluted - as in the past with a brush, so that the facades show the craftsman's process of creation. A slightly different shade of yellow was used on the projecting plaster surfaces than on the recessed surfaces. This fine differentiation emphasises the plasticity of the facades.

Discovery in the basement

Before construction began, archaeological excavations took place on the site of the former castle. Remains of the cellar and catacombs came to light, as well as remains of an old monastery that had once stood there. The wall sections were secured, restored and covered with a concrete ceiling. Today, visitors can delve deep into the past there and see a separate exhibition about the history of the place. The ceiling was given a black-grey coat of KEIM Optil, which is inconspicuously restrained and allows the original components and exhibits to take precedence in terms of design.

Products used in this project

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