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New ‘coat’ keeps limestone from eroding

CARDIFF U. (UK) — A new treatment for historic limestone buildings protects them from erosion by acid rain and atmospheric pollutants while allowing the stone to “breathe.”

Working on York Minister’s iconic magnesian limestone cathedral, Karen Wilson and Professor Adam Lee of the School of Chemistry have developed the new treatment by utilizing “hydrophobic surface coatings.”

“Iconic buildings such as York Minster are suffering from the effects of weathering by atmospheric pollutants,” according to Wilson, who led the research.

“York Minster is one of the largest Gothic cathedrals in Northern Europe, and has occupied the same site since 600 AD. Along with many other historic structures of its era, York Minster is eroding at a noticeable rate, and periodic renovations and attempted restoration efforts using the best materials available at the time have, in some cases, accelerated the decay,” she adds.

Using a single layer of fatty acids combined with another fluorinated chemical compound, the Cardiff University team, in collaboration with scientists from the University of Iowa and Diamond Light Source, have developed hydrophobic and super hydrophobic surface coatings for calcite (a common form of limestone) that delay the formation of damaging gypsum crusts by sulphur oxides.

When applied to 19th century stone from York Minster, the same coatings repel sulphuric acid permeation.

The research, funded through the EPSRC/AHRC Science and Heritage Programme and published in the journal Scientific Reports, could now be used to help conserve other historic limestone buildings around the world.

“You only have to look at Cardiff’s Cathays Park civic center and Cardiff University’s own Main Building to see the number of historic limestone buildings we have here in Wales,” says Wilson.

“Wales, like many other parts of the UK, also has an abundance of beautiful limestone churches, cathedrals, and other landmark buildings. We hope our work at York Minister will offer a new treatment to preserve limestone buildings across Wales already suffering from the effects of erosion.”

Source: Cardiff University

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