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Bonn uni renovations: Specialised restorers work on ornate Koblenz Gate

Bonn uni renovations : Specialised restorers work on ornate Koblenz Gate

The richly decorated Koblenz Gate at Bonn University is currently hidden by scaffolding. The historic façade is in need of renovation. For this, the building and property management company ‘Bau- und Liegenschaftsbetrieb’ (BLB) NRW is relying on the support of restorers and specialised companies.

Hundreds of motorists and cyclists pass through the historic Koblenz Gate every day. Since last weekend, the passageway with its golden columns and sculptures has been concealed behind scaffolding. Nick Westerhelweg from the Cologne branch of the Bau- und Liegenschaftsbetrieb (BLB) NRW which is responsible for the restauration, explains what has to be taken into account during renovation of the gate. Over the years, wind and weather have left their mark on the listed building, which now has to be renewed and restored.

The extensive work on both the façades will take about a year, says Westerhelweg. “Some of the upcoming work can only be carried out at certain temperatures or in dry weather, so the duration of the renovation is highly dependent on the weather.” Traffic on the B9 will not be affected again until after the renovations, when the scaffolding will be dismantled. BLB NRW will provide information about this in good time.

Construction work will also continue to be part of the university's operations. The façade of the rest of the main building will be renovated in the near future. There is also constantly work to be done at the Faculty of Education on Römerstraße, which the university is using as temporary accommodation until further notice and whose final future is still unclear.

Following setting up the scaffolding on the Koblenz Gate, the next step is to remove the damaged plaster so that the exposed masonry can dry. The BLB is speeding up this process with the help of infra-red heaters and heating rods, reports Westerhelweg. “Only then, where necessary, can the natural stones be consolidated, and the cracks and joints refilled.” Afterwards, the façade will be plastered and repainted.

Westerhelweg explains that there are many other special restoration steps that restorers and other specialised companies carry out on the ornate gate. “The work on the masonry of the Koblenz Gate, for example, is comparable to that on historic churches and requires the same expertise.” For example, the specialists clean the natural stones on the balustrades on the gate roof, and carefully rework the gilded ornaments. BLB NRW is coordinating with Bonn city’s heritage protection authority on how the renovation will proceed and which materials will be used.

To ensure that the façade is not so badly affected by the weather in future, the masonry is also being sealed, says Westerhelweg. In addition, the sheeting on the entire gate will be renewed so that rainwater can drain off better.

Bonn gilder Wiebke Nett restored the lions and crown of the Old Town Hall several years ago and is proud of her work. “They're still bright gold,” she says. Nett explains what is important for gilding to be able to withstand the wind and weather. Rule number one: linseed oil. “Rain beads off the oil,” says Nett. The gilder must not use protective varnish as this would affect the oil. In addition, the gold should be as pure as possible. According to Nett, the gold leaf must have at least 23.5 carats. To put this into context, the highest carat number is 24. "Pure gold is more weather-resistant," explains Nett. "I always say: then it will last 100 years."

And what else does a gilder need on a job like this? "You have to have a head for heights," says Nett and laughs. “The first day on the scaffolding is tough, but eventually you do jump from board to board.”

(Original text: Christine Ludewig, Translation: Caroline Kusch)