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 means it is easily damaged and safe, effective solutions to conservation issues can prove difficult to find.
Over the years, Royston Cave’s carvings have seen significant loss of detail. Edges now appear softer and more rounded, particularly noticeable with facial features. In some cases, elements have almost been entirely lost.
Most damage appears to be caused by fluctuations of moisture in the cave, resulting from water ingress, which causes minor structural changes and internal pressure in the chalk. This creates fine, hairline cracks between the raised carved detail and the cave wall. The cracks are then colonised by worms and microbiological growth, 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.
Heritage at Risk
In 2018, Royston Cave was added to the Heritage at Risk Register. The register highlights the heritage sites most at risk, in an attempt to protect them.
What is chalk?
Chalk is a soft, white, rock. It is made from the skeletal remains of plankton, compressed together over millions of years.
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 drainage systems above. Repairs were made which significantly reduced the frequency of flooding and severity of water ingress.
During heavy rain, leaks 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. It is therefore accepted that some water ingress will always occur in this type of subterranean site.
Extensive areas of microbiological growth can be observed in the cave. Most of the material is black or brown in colour and is most noticeable near light, indicating the photosynthetic nature of the organisms.
Microbiological growth of this type is not only aesthetically unpleasant but can cause physical deterioration as it attaches itself to the chalk.
Treatment with biocides may have a negative effect on the chalk so the 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 Fungas Gnats
Significant damage has been caused by worms ingesting the chalk. In some areas, whole sections of the chalk surface has been eaten away and its detail lost. They are thought to feed on nutrients in the chalk which enter the cave as a result of leaks and flooding, especially from sewage pipes.
Soil and dirt was removed from the base of the cave and from horizontal surfaces in the cave wall to reduce their habitat. This also revealed a number of additional floor carvings, some showing lying figures.
Larvae found in the cave were identified as a type of Fungus Gnat. This species are almost always associated with cave-like habitats. A UV insect lamp is used to attract and trap them in their flying adult stage. This interrupts and limits their breeding cycle reducing the reproduction of new larvae. The lamp
operates on a timer to minimise microbiological growth.
Until the mid 20th century, visitor access to Royston 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 disperse visitor-generated CO2 levels. A filter prevents large debris from entering the cave and is cleared regularly to prevent blockages.
Despite the cave’s relative stability, small moisture 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.
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 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, and periodic photographic surveys are undertaken to assess the ongoing rate of deterioration.