X-rays are being used on parts of York Minster in an effort to protect the historic building from further erosion.
Researchers are using the equipment to find out how badly the Minster's limestone structure has decayed.
The results will be used to help advise conservation experts how further decay can be avoided.
Dr Kate Giles from the Department of Archaeology at York University, said: "Our aim is to preserve as much of the medieval Minster as we can."
Erosion has been a fact of life for the Minster since it was first built in medieval times but in the past 200 years that has been made worse by pollution.
Dr Giles said: "If you imagine, like in a hospital, what we're doing is looking at the composition of the stone but also the historic mortars that are between the stones in the Minster.
"We can actually look at the chemical composition of these things very closely to work out what's happening inside the stone and inside the mortar and how that's accelerating the processes of decay."
The X-ray project is being led by Cardiff University's School of Chemistry and the work is a collaboration with York University's Department of Archaeology.
It will take three years to complete and it is hoped that the research will also help conservation experts decide what materials to use while restoring the East Front.
Dr Giles said: "Where we need to actually replace stone we'll have an informed understanding of what's happening to it and why we need to do that."