Royston Cave is a Grade I listed, scheduled monument. This means it is a protected site of national importance. The cave is cut into chalk; a very soft and porous rock. The nature of chalk makes it highly susceptible to damage and safe, effective solutions to conservation issues can prove elusive.
Over the years, Royston Cave’s carvings have seen significant loss of fine detail and sharp edges. All carvings now appear softer and more rounded, particularly noticeable with facial features. In some cases, figurative elements have almost been entirely lost.
It appears that fluctuations of moisture in the cave, resulting largely from water ingress, create minor structural changes in the chalk. This leads to internal stresses which creates fine, hairline cracks between the raised carved detail and the cave wall. The fissures are then colonised by microbiological growth and larvae, causing the cracks to enlarge. Eventually these sections of chalk crumble away. Although this process is relatively slow, it appears constant and ongoing, and further loss is likely to take place.
WHAT IS CHALK?
Chalk is a soft, white, porous rock. It is made from the skeletal remains of plankton, compressed together over millions of years!
Original Entrance Shaft
HERITAGE AT RISK
In 2018, Royston Cave was added to the Heritage at Risk Register. The programme identifies and highlights those sites most at risk in an attempt to protect them.
Reclining FIgure, 1952
Reclining Figure (damaged), 2009
Fungus Gnat, © Tobit Curteis Associates
Royston Cave has been subject to severe flooding on a number of occasions. This was determined to be largely the result of the failure of the drainage system above. Repairs were made which significantly reduced the frequency of flooding and severity of water infiltration.
During heavy rain, water ingress and flooding still occur. Because of the porous nature of chalk, and the bedding planes it contains, it is difficult to prevent all water ingress and is accepted that water penetration will always occur in this type of subterranean site.
Extensive areas of microbiological growth can be observed in the cave. Much of the material is black or brown in colour. This is most noticeable near light, indicating the photosynthetic nature of the organisms.
Microbiological growth of this type is not only aesthetically damaging but can cause physical deterioration as it secures itself to the structure.
Treatment with chemical biocides would erode the chalk and pose public health and safety issues, so the microbiological growth is tackled by limiting the use of the cave lights and using biocidal UV lamps. In recent years, the microbiological growth has worsened. This may correlate with increased visitor numbers.
WORMS AND GNAT LARVAE
Serious damage has been caused to Royston Cave by worms. In some areas, whole sections of the chalk surface has been eaten away and its detail lost. Soil and impacted dirt was removed from the cave floor and horizontal surfaces to reduce their habitat.
The removal of soil revealed a number of additional floor carvings, some showing lying figures. It also uncovered numerous small holes in the chalk, some of which are clearly man made.
Fly and larvae found in the cave were identified as a type of Fungus Gnat. This species are almost always associated with cave-like habitats. The larvae leave deposits on the surface of the carvings which are particularly disfiguring. Treatment with a chemical pesticide would erode the chalk and pose public health and safety issues. Instead, a UV lamp is used to attract the adult flies, removing them from the cave, and limiting the breeding cycle. The lamp now operates on a timer to minimise microbiological growth nearby.
During the 18th and early 19th centuries, access to the cave was often uncontrolled. During this period the cave walls suffered extensive vandalism and graffiti. It is possible that alterations were made to some carvings but, due to subsequent deterioration, it is impossible to determine where this may have taken place.
AIR AND MICROCLIMATE
A study of the microclimate inside the cave indicated that conditions are relatively stable. The average temperature remains at approximately 12.5°c throughout the year, with average humidity levels in excess of 90%.
A grille in the cave ceiling allows sufficient natural ventilation to dissipate visitor-generated CO2 levels. A filter prevents large debris from entering the cave and the filter is cleared regularly to prevent blockages.
Despite the cave’s relative stability, small fluctuations do still occur and, while this continues, it is likely that slow deterioration will take place. As a result, the carvings will need infrequent, but occasional, treatment.
Existing cracks and vulnerable surfaces from previous losses have been re-adhered or consolidated. This treatment focused on stabilising small areas where there was most significant risk of loss, particularly around some of the raised features. This was undertaken with lime based mortars and nano lime dispersions to ensure compatibility with the carvings, minimise variations in porosity, and provide similar visual appearance. Further remedial treatments may be required in the future to prevent further losses to the carvings.
Conservation of Royston Cave is our paramount concern. We continue to monitor water ingress and maintain environmental controls to stabilise the microclimate. The ventilation grille is cleaned on a regular basis in order to prevent blockages, CO2 levels are periodically checked, and the continued use of the UV biocide lamp maintains a low gnat population. Regular condition surveys are carried out to highlight whether intervening treatment is required, to ensure micro-cracks are stabilised before major fractures or significant losses take place.
A complete photographic survey of Royston Cave has been undertaken by English Heritage, and a detailed topographical survey has also been carried out. We aim to utilise close range laser scanning to create a highly accurate 3D model of the cave, to be used critically in the preservation and education of Royston Cave. Future periodic condition surveys and laser scans will assess the ongoing rate of deterioration.
We believe long term conservation can be viewed in three distinct phases; preventive measures to control the underlying causes of deterioration; treatment to stabilise damaged areas; and long term assessment, to monitor the condition of the cave and control new issues before significant damage occurs.
We would like to thank all teams, particularly Historic England and Tobit Curteis Associates, who have contributed to the conservation of Royston Cave and who continue to help preserve this unique monument for future generations.
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