How the weathered stonework of the historic York Minster could be preserved… using olive oil
09:51 GMT, 30 November 2012
Conservationists have come up with a novel way of preserving the crumbing walls of the historic York Minster – coat it with olive oil.
The naturally derived ingredient is known for being a key part of a healthy diet as well as beneficial when smoothed on to the skin and hair.
But now scientists claim it would be a 'cheap and simple' way to repel water and pollutants from ancient rock.
Fresh idea: York Minster could be painted with a 'hydrophobic' substance to repel water but allow the stone to breathe
The building was constructed between 1220 and 1470 using mainly magnesian limestone, but this material, together with limestone, is prone to attack by pollutants such as oxides of sulphur in rain.
Pollutants locked in the stonework can rise to the surface in the form of sulphates and crystallise in small cracks and crevices, weakening the stone, which is then broken down and washed away by rainwater.
Versatile: Olive oil is known for its health-boosting properties – but now it could be used to benefit famous architecture
Researchers from Cardiff University
said: 'In common with many historic structures of its era, the exterior
stonework of York Minster, the largest Gothic cathedral in northern
Europe which has occupied the same site in England since 600 A.D., has
suffered extensive weathering by atmospheric pollutants.'
Linseed oil has previously been used to
conserve York Minster, but was found to darken limestone and reduce
salt permeability, stopping the porous rock from 'breathing' and promoting mould and decay.
They proposed the use of 'hydrophobic surface coatings' such as 'naturally sourced free fatty acids'.
These, it was suggested, would protect from acid rain but not block the stone microstructure.
The Minster has had some restoration work over the years, but it is thought this could have accelerated erosion.
Dr Karen Wilson, co-author of the report and formerly of York University, said: 'It’s long-term work. The next step is carrying out field studies by testing the Minster walls on site over the next few years.
'We’ve got the proof of our principle, our work with the Minster wall samples was a great success, now we just wait and see.'