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A coating from the kitchen cupboard may help conserve historic limestone buildings around the world.
Scientists from Cardiff University in Wales, UK, say they have developed a new treatment using hydrophobic surface coatings, like those found olive oil, to protect historic limestone buildings from acid rain and other pollutants.
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Andy Barrett / WikiMedia Commons |
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Scientists say a coating of olive oil could help protect historic architecture from decay. The team tested limestone samples from York Minster, one of the largest Gothic cathedrals in Northern Europe.
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The coating technology also allows the masonry to “breathe,” the team reports in “Preservation of York Minster historic limestone by hydrophobic surface coatings” published in the journal Scientific Reports.
The team tested its theory on 19th-century limestone from the eroding York Minster, one of the largest Gothic cathedrals in Northern Europe. The building was constructed between 1220 and 1470 using mainly magnesian limestone and underwent a major restoration beginning in 1802.
Crumbling History
“Iconic buildings such as York Minster are suffering from the effects of weathering by atmospheric pollutants,” according to Dr. Karen Wilson, who led the research team.
“Periodic renovations and attempted restoration efforts using the best materials available at the time, in some cases, accelerated the decay,” Wilson added.
For example, linseed oil has been used on the cathedral, but it was found to darken the limestone, reduce salt permeability, and promote the growth of mold and decay.
Why Olive Oil?
A component of olive oil, known as oleic acid, reacts to limestone surfaces, according to the researchers.
Wilson’s team used a single layer of fatty acids combined with another fluorinated chemical compound to develop a water-repellent, breathable coating for calcite (a common form of limestone).
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Joanne Bergenwall Aw / WikiMedia Commons |
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Linseed oil used to protect York Minster actually darkened the limestone and promoted the growth of mold and decay, the researchers note.
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“It produces a nice barrier coating that stops water penetrating into the pores of the actual stone itself,” said Wilson.
Testing a ‘Great Success’
The team tested a small sample of stone from the cathedral with the new coating and exposed the stone to sulfuric acid.
X-ray absorption analysis showed that the calcium minerals remained largely protected from the acid, according to the report.
“We’ve got proof of our principle, our work with the Minster wall samples was a great success, now we just wait and see,” Wilson told a local news outlet.
The Cardiff team also collaborated with scientists from the University of Iowa and the UK science facility Diamond Light Source on the research. The researchers plan to carry out field studies by testing Minster walls on site over the next few years.
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