Lime mortar
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Lime mortar to restore historic buildings

Scottish researchers have been taking lessons from the past to keep the country's historic buildings standing.

Historic Scotland has been collaborating with Heriot-Watt University to find 21st century ways of using lime mortar.

It holds together most of Scotland's historic buildings and 20% of its housing stock. It fell from general use in the 1920s, but now science is helping it make a comeback.

BBC Scotland's science correspondent Kenneth Macdonald reports from near Bonchester Bridge in the Borders.

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