Läckö Castle to be refurbished with the aid of conservation research

Läckö Castle makes quite an impression even from a distance. Majestic in white, it looms large against the blue sky. The fact that the façade needs repairing isn’t obvious from a distance. It’s hard to guess that a painstaking refurbishment project is under way with the aid of conservation research and a contract education programme provided by the University of Gothenburg.
“This has been one of the most challenging and fun things I’ve done,” says Jonny Eriksson, project manager for the programme and Senior Lecturer at the Department of Conservation.

He meets us in the castle’s car park and escorts us a couple of hundred metres to the work site, where piles of grey stone blocks are stacked next to a work shed. However, the scene is dominated by the massive brick kiln. In it, grey limestone from Kinnekulle is transformed and shortly thereafter applied to the façade of Läckö Castle.

Läckö castle’s façade was last refurbished in the 1970s. Today, the façade is turning grey and the render is letting in penetrating damp. To ensure the refurbishment conserves the building’s cultural heritage, a contractor with knowledge of antique render was required. But no such contractor could be found. That’s why castle architect Allan Ahlman approached Jonny Eriksson at the University of Gothenburg and asked him to provide a contract education programme.

“The Department of Conservation has been involved in research at Läckö on the use of antique craftsmen’s methods for around 20 years. First with researcher Eva Malinowski, and I’ve been involved since 2005,” says Jonny Eriksson, who has a background as a plasterer. His thesis entitled Kalkbruk – krympsprickor och historisk utveckling av material, metoder och förhållningsätt (Lime render – shrinkage cracks and the historical development of materials, methods and approaches) was published last year.

One of Sweden’s biggest rendering companies, Puts & Tegel, was awarded the refurbishment contract following a public procurement process. Three of the firm’s plasterers participated in the programme. The basic premise was that render produced using antique craftsmen’s methods could be adapted to modern production conditions.

“We started the programme with a trip to Kinnekulle, where we selected suitable limestone, crushed it and sorted it into different fractions. Then we packed the kiln and started it up,” says Jonny Eriksson.

There is a slightly worrying creak as we climb a rickety ladder to come up to the level of the kiln’s roof. Jonny carefully moves aside the sheet metal roof, which is in place to protect the kiln and prevent moisture getting inside if it rains. Visible below is a space measuring six cubic metres where the limestone is packed in and burnt.

“No mortar is used between the bricks in this kiln. All the bricks are just stacked on top of each other so that the kiln can be disassembled and reassembled elsewhere.”

. It is vital that the firing temperature is between 930 and 960 degrees Celsius. Afterwards, the burnt limestone is packed into well-sealed barrels to be slaked with water in the next stage.

This is where the grey limestone of Kinnekulle changes colour to a golden yellow. It is vital that the firing temperature is between 930 and 960 degrees Celsius. Afterwards, the burnt limestone is packed into well-sealed barrels to be slaked with water in the next stage. A chemical reaction then forms a putty, a binding agent that is mixed with sand to become mortar, which is then used to render the walls of the castle.

The plasterers have had the opportunity to test the method and materials on a 25 square metre trial surface.
“The trial surface has acted as a palette where we’ve been able to test the recipe for the mortar. We have looked at how the mortar works with the machines, how it bonds to absorbent and non-absorbent bases, and many other parameters.”

It is a mild, clear day without a breath of wind. There is an earthy smell of autumn. The crunch of gravel under our shoes can be clearly heard as Jonny shows us around the site. He explains that the first firing of the kiln last November offered a few surprises.
“We had to deal with the challenges that reality can throw at us. We were able to see what worked the way we expected it to, and what we needed to change.”

The contract education programme included methodological development, which is something Jonny is continuing through the supervision of the refurbishment.
“If you work the way we do, then the research questions arise out of the actual work process. There’s no other way to develop them.”

We leave the work site and slowly stroll up towards the castle. The leafy trees on Kållandsö island are blazing with colour on this autumn day: warm yellow, bright orange with a splash of red. In the midst of all this colourful splendour is the fairytale-like castle.  Lake Vänern with its intense shade of blue shines on all sides. The castle was originally built as an episcopal castle in 1298, but its current aspect dates from the 1650s.

Once at the entrance, you notice the scaffolding. It covers the part of the façade where the castle chapel is located. Here you can see that the pale cream-coloured mortar that Jonny and the plasterers from Puts & Tegel have prepared is slightly less white than the render on the rest of the castle.

“Our mortar is very close to the original render used in the 17th century. In the 1960s and 70s, the castle was refurbished using titanium white, cement and mica, but that’s not how the castle looked originally.”

A lot of parties are involved in the refurbishment project: architects, curators, the Swedish National Heritage Board, the Läckö Castle Foundation and the National Property Board of Sweden, which owns the building. There is a desire for consensus, but sometimes opinions diverge.

“For example, we’ve had a big discussion about the colour of the façade. I like the soft, pale primary colour in our mortar. Others think we should paint it with lime wash to make it lighter. We haven’t made the final decision yet,” says Jonny Eriksson.

Läckö castle needs a new façade

WHAT Läckö Castle is getting new render similar to that originally used in the 1650s. This refurbishment is being made possible thanks to conservation researcher Jonny Eriksson having taught plasterers at the firm Puts & Tegel how to produce the render using methods that the original plasterers would have used.

WHEN The contract education programme began in August 2019 and lasted for just on one year. Puts & Tegel, the contractor whose employees participated in the programme, has now begun its refurbishment of the castle. Jonny Eriksson is supervising and inspecting the work.

WHY To preserve historic buildings and pass down antique craftsmanship to modern tradespeople. Render and mortar have a thousand year long history in Sweden. Being able to produce the render in the traditional way is important in maintaining the authentic appearance of cultural heritage buildings.

Jonny Eriksson

IS: Senior Lecturer at the Department of Conservation

In the news because: He is Project Manager for a contract education programme for plasters.