Restoration glass for a reconstructed city building

Project | Material

The background

The city quarter located between Frankfurt’s cathedral [Dom] and city hall [Römer] was a vibrant space in the historic city center with opulent patrician houses, old-style side streets and picturesque courtyards – until its destruction the Second World War. To reclaim the quarter’s vibrancy for this modern metropolis on the river Main, a major urban planning project was established in 2007. From 2012 – 2018, an area in the historic old city covering 7000 m2 was to be reconstructed.

Among the 15 buildings to be restored is the Haus zur Goldenen Waage that had been the city’s most well-known tourist attraction (Markt 5). The core of the building is a timber-framed construction from the Middle Ages that had undergone reconstruction up to 1619 by its eventual owner, the wealthy spice trader and confectioner Abraham von Hameln. It received an opulent Renaissance facade and lavish timber framing and was crowned with a Rhenish waved gable.

The solution

The firm carrying out the work, Kramp & Kramp based in Lemgo, opted for restoration glass from SCHOTT for the glazing. The firm PaX constructed the windows and doors.
 

• The exterior window panes of the new box windows used single-pane restoration glass.
• The interior panes used triple glazed glass with corresponding thermal insulation (Ug=0.5 W/m²K) and the latest fittings technology.

For the glazing, SCHOTT’s TIKANA^® restoration glass and RESTOVER^® light was used. This glass is machine drawn using the traditional Fourcault process which, in contrast to float methods, intentionally results in irregular glass surfaces (longitudinal undulations) and thickness. This produces characteristics shared with the glass originating from the different epochs while also enabling a range of processing options to fulfill construction and financial constraints.

Choosing the right glass requires not only consideration of historical contexts but also how the building is going to be used in the future. The lightly structured glass products TIKANA^® and RESTOVER^® light were therefore chosen for the “Goldene Waage” project.
  

• TIKANA^® is otherwise particularly suitable for buildings in the Bauhaus style. Its slightly irregular surface blends harmoniously into classical modern buildings.
• RESTOVER^® resembles window glass manufactured at the turn of the century. Its small thickness allows easy installation in historical window frames and profiles. The portfolio is completed by the RESTOVER^® light variant, whose surface is less structured and less similar to mouth-blown glass than the RESTOVER^® plus variant.
  
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A total of 390 panes of SCHOTT restoration glass, with a special s-form lead coating (Karniesblei), were used to cover a window area totaling 110 m2. This has given the facade a coherent look despite the use of modern insulated glazing on the interior panes. A special color tone was applied to the wooden surfaces as well as to some of the fittings to give the windows a highly impressive and unique appearance.