The Cochno Stone

West Dunbartonshire Scotland, UK
In collaboration with the University of Glasgow

In early September 2015, Factum Foundation and the University of Glasgow archaeology department undertook a test excavation of the Cochno Stone. Considered to be one of the largest (8 x 13 m) and finest sets of Neolithic or Bronze Age (3000 to 2000 B) cup and ring petroglyphs in Scotland, the stone was sadly reburied in 1965 to protect it against vandalism.

A video by May Miles Thomas on the test excavation of the Cochno Stone

First excavation test

The excavation test aimed to assess its current state of preservation in order to plan a full excavation. Within the 4x1m area excavated, evidence of graffiti led to broader implications for the recent history of interaction with the ancient monument.

Kenneth Brophy (Senior Lecturer in Archaeology at the University of Glasgow) explaining to school children the history of the Cochno Stone and the Factum Foundation's aims for the future.

The majority of images of the Cochno Stone originate from archaeologist Ludovic MacLellan Mann, who visited the site in 1937 and researched his ‘archaeo-astronomical’ theories by painting on the cup-and-ring markings. Photographic evidence led to initially believing the markings to be white. Still, recollections from the local community suggested that Mann had also included red, blue and even green for his colour-ins.

The test excavation not only found the sandstone in good condition and under less earth than expected, but also deepened the understanding of the significance of the Cochno Stone’s biography within its local context. Over the three days of the excavation, a large number of people visited the site and shared childhood memories and theories from before the 1965 re-burial. As a result of the test, Historic Scotland and West Dunbartonshire Council both permitted to continue the excavation through the ‘Revealing the Cochno Stone’ project and hopefully produce a facsimile that would ensure the legacy of this extraordinary monument for the future.

In 2016, the project gained worldwide attention, with the story rapidly going viral in numerous reports in print, radio and television – reaching as far as Tasmania. The project was also brought to the attention of the Scottish Parliament by the local MSP, Gil Patterson, in recognition of the importance of the work being undertaken. (Read more on the Clydebank Post).

Coverage on BBC News Scotland

Plan of the Cochno Stone with the excavated area highlighted

Ludovic Maclellan Mann painting in the markings in 1937

Map showing the location of the Cochno Stone in West Dunbartonshire

The full excavation

The excavation began on September 5th with a team of students from the University of Glasgow Archaeology Department, led by Dr Kenny Brophy, working with Green Light Environmental Ltd. Factum Foundation also contributed, with help from Ferdinand Saumarez Smith, Tom Don, Dani Trew and with stone conservator Richard Salmon providing technical advice.

While the wet weather made working conditions difficult, the Cochno Stone was slowly revealed after three days. The final cleaning was carried out with the help of the Clydebank Fire Department.

One of the most exciting parts of the cleaning process was the revelation of evidence of Ludovic Maclellan Mann’s paint markings, with yellow lines radiating out from the area at the highest point that he believed to be of the greatest importance for interpretation, red horizontal lines crossing these rings marked in white and some cups marked in green. The most visible areas of this were towards the edges of the stone's perimeter on the left-hand side in the middle (as pictured above) and on the right-hand side towards the top. This was a particularly significant finding in that it provides material evidence for an informed reconstruction of the markings, supported by the photographic evidence. It also presses more questions about how long his markings were left on the surface of the stone following their application in 1937.

Removing the bulk of the soil from the stone with a mini digger.

A fire-fighter from the Clydebank Fire Department cleaning the surface of the stone, directed by Richard Salmon

Recording

With the stone cleaned, Factum Foundation proceeded to record the surface using different sets of digital data:

Drone photogrammetry proved quick and effective in generating a first 3D model of the surface of the stone for general communication and project coordination. While the data is considered low-resolution for Factum Foundation’s standards, it was nevertheless impressive in providing a broad map of the surface onto which higher-resolution data could be aligned.
High-resolution photogrammetry, carried out in sections using a photogrammetry rig. A simple horizontal rig with a step motor operated a Canon 5DS R camera and ring-flash along the length of the guide, taking periodic shots of the surface of the stone. Strips were marked off, working from the lowest to point up breadthways along the length of the stone. This required the tripods to be adjusted and readjusted to get the correct level for the recording at each new position.
LiDAR laser scanning, often used in archaeological excavations, was carried out by Scottish Ten with a Leica P40 to map the entirety of the stone and its immediate surroundings, providing an extra reference to ensure the geometric accuracy of the entire model.

When the 3D data layers were processed and merged at Factum Foundation’s studios in Madrid, an accurate, complete and high-resolution viewer of the Cochno Stone was created for study and dissemination purposes. In addition to the new photographic evidence collected on site, the data is of enough quality that a facsimile of the Cochno Stone could be produced if the need ever arises.

The stone was later re-buried with a geotextile laid across its surface and a thin layer of soil evenly distributed under the spoil. A ceremony led by dowser Grahame Gardner accompanied the stone’s return to earth, where it will lay waiting for a new future.