Collyweston slate research looks to bring back unique roof stone
Sat on rooftops in historic villages, churches and stately homes, Collyweston slate has helped define the look of some of England's most well-loved traditional buildings.
Starting out in the Northamptonshire village of Collyweston centuries ago, mining for the slate throughout the East of England hit its peak in the late 1800s.
But it stopped altogether in the 1970s, with extraction of the distinctive limestone becoming commercially unviable.
Now English Heritage and other partners are researching whether mining could become commonplace once again, by seeing if they can speed up the timely process of the rock being ready for the roof.
"We've been testing for about a year and we're trying to get the process of the stone being prepared for roofing from three years to within a few weeks," said Chris Wood, head of buildings conservation and research at English Heritage.
"We have got a lot more work to do - this is essentially only testing and trying to get the method right.
"It was very successful in the lab, but to do it on a basis where it might be commercially attractive is a lot more work."
To get the stone prepared, Mr Wood said it traditionally used to be left outside for three winters until the frost revealed layers that could be broken into perfectly flat slates.
But by dousing the rock in water and then putting it in a large freezer, tests have shown the natural freeze-thaw process can be sped up significantly.
"It has tremendous potential to be commercially viable again and we're confident the process can be refined," said Mr Wood.
"There is huge demand for the slate because it's a unique stone and there is potentially a big market to tap into.
"There are hundreds of buildings around Northamptonshire, Lincolnshire, Cambridgeshire and even in London and east Yorkshire that still have the slate on them.
"But because supply is so low, it's made it expensive and many old unlisted buildings are being stripped of Collyweston which is harming the historic environment."
Mr Wood said it was becoming the desire of planners and residents in historic areas for Collyweston slate to be used again in new housing, so their look is kept in line with older buildings.
He said the research has a few more months remaining, but hopes a successful outcome can lead to Collyweston slate being seen on buildings for years to come.
"We want to maintain the distinctiveness of roofscapes in historic areas and there's an impetus to reduce the loss of materials from unprotected buildings," said Mr Wood.
"It's a highly sustainable and green industry and hopefully an active market can start once again with apprentices learning new skills and rural areas having greater employment prospects".
See more on the history of Collyweston slate and the efforts to rejuvenate the industry on Inside Out, on BBC One in the East on Monday at 19:30 BST.