Using 3D scanning to preserve York Minster’s heritage

Challenge

York Minster wanted to improve its process for repairing and replacing damaged grotesques. It asked the University of Sheffield Advanced Manufacturing Research Centre (AMRC) to help it decide how to use 3D scanning to save its stonemasons time and money.

Background

York Minster is one of the largest Gothic cathedrals in the world, its huge walls adorned with stone characters known as grotesques and gargoyles (the difference is that the latter feature a water spout). Many of these are hundreds of years old and represent some of the most historically significant sculptures in the UK. But sitting outside in all weathers, they suffer from erosion and often need replacing or repairing.

Increasingly severe rainfall due to climate change is leading to increasing erosion. The medieval guttering, fit for purpose for centuries, can no longer remove water fast enough. This leads to leaks and causes the stone to fail sooner than it would have in the past.

Replacing the grotesques involves stonemasons chiselling the stone to get to the grotesque, removing it, and recreating it in their workshop. Many of these grotesques are at great height — at its highest the building is more than 70 metres tall — so this is difficult and time-consuming work.

The Minster was keen to make this vital conservation work more efficient with modern technology. A 3D scanner would allow the Minster's stonemasons to record stones at varying points in their lives, from freshly-carved grotesques to hundred-year-old, well-weathered stone coming off the building. By producing a detailed scan of a grotesque before it was removed from the wall, its staff could also create a lifelike version to work from in the safety of their workshop.

With so many scanners on the market, they weren’t sure where to start, so they turned to the AMRC’s experts to help.

Innovation

The engineers at the AMRC were quick to understand the benefits of 3D scanning for the stonemasons. The scans make it possible to see more detail in the stone. The scan can then be used to CNC the basic shape of a grotesque in polyurethane modelling block, before the stonemason completes the fine detail. This takes away the less skilled and more onerous elements of the task and leaves the stonemasons to concentrate on their craft.

The AMRC analysed how four different 3D scanners worked in the uniquely challenging environment of the Minster. High in the air on freestanding scaffolding, four scanning companies produced accurate scans of the same moss-covered grotesque. The AMRC’s engineers then studied the results to determine the best scanner for the Minster to use.

Result

Through the comparison of the four scanners, it became apparent that the price did not necessarily correlate with the quality. They found that the lowest cost scanner was able to compete with the most expensive. Their detailed analysis also highlighted the quality of the data down to very small details, allowing for an excellent 3D scan to be produced.

Based upon cost, scan quality and ease of use up on the scaffold, the AMRC recommended the best scanner for the stonemasons’ purposes. The Minster duly bought the scanner with the highest quality results.

The scanner is now being used to create accurate scans of individual blocks on the Minster to be 3D-printed or cut on a CNC saw to assist in vital repairs, and record important historic features of the Minster's fabric for future generations.

Impact

This project has allowed York Minster to future-proof its processes using modern recording technology. It helps the stonemasons in their day-to-day conservation of this extraordinary building, while also creating a historic record for future generations. It has also significantly reduced the cost of their repair work.