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One of the big challenges of our time is figuring out how to preserve our history. In Europe, that means protecting some glorious buildings that date back to the Dark Ages.

From London, NPR's Philip Reeves has the story of a team of scientists who hope to do just that, with a little help from one of the world's most basic cooking ingredients.

PHILIP REEVES, BYLINE: The British have some stunning cathedrals. York Minster, in the north of England, is one of the most magnificent of all. They began building it 800 years ago. Two-and-a-half centuries later, work was complete.

The result was one of Europe's largest Gothic cathedrals.

(SOUNDBITE OF CHURCH BELLS)

REEVES: There's something very confident about the sound the bells of York Minster, yet the cathedral has had a rough ride through history. It's been pillaged and looted. There have been devastating fires and lightning strikes. Today, there's another threat: acid rain.

The medieval craftsmen who built York Minster used rock from a nearby quarry. It's a type of limestone particularly vulnerable to damage by atmospheric pollution. The cathedral stones are decaying. British scientists and archaeologists have teamed up to try to find a solution.

We're not talking here just about the pollution created by this modern car-crazy age. You see, limestone has a memory. Locked within the stones of York Minister are the residues of pollution churned out in the 19th century, by the factories and power plants of Britain's Industrial Revolution. Those residues slowly permeate to the surface of the stone with alarming effect.

KAREN WILSON: All the salts can actually build up in the microstructure of the stone and eventually crack it, and large pieces will start to fall off the building.

REEVES: That's Dr. Karen Wilson from Cardiff University in Wales. She heads a research team trying to develop a protective coating for York Minster and other ancient buildings. They want something that's water-repellent and keeps out that acid rain. But they also need it to let the limestone breathe, allowing the nasty stuff from the Industrial Revolution to escape.

Protective coatings have been tried before over the last century or so. One idea was to oil York Minster. They experimented using linseed oil. This damaged and discolored the stone, making it darker. But it did give Wilson and her team an idea. They turned to the kitchen cupboard and came out with...

WILSON: Olive oil.

REEVES: That's right, olive oil. Wilson can explain the science.

WILSON: The main component of olive oil is something called oleic acid. And the nice thing with oleic acid is it has one end of it that will selectively react with the stone. And then another end - which is a very long hydrocarbon chain - will give you the hydrophobic properties to repel the water.

REEVES: The oleic acid gets mixed with another substance to create the protective coating. Tests have been carried out using samples of the cathedral's stone. Wilson says it's early days but the results are looking good.

What a nice thought: One of the world's greatest Gothic cathedrals somehow survived all that pillaging and all those fires. And now, maybe, it'll stand for another 800 years, thanks to a little salad dressing.

Philip Reeves, NPR News, London.

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