Billingsgate House and Bathhouse is one of the many archaeological sites hidden beneath the streets of central London. This remnant of Roman Britain can be found in the basement of a rather unassuming office complex on Lower Thames Street, between Monument and Tower Hill.
In the 3rd century, when this House was built, it would have been right on the banks of the River Thames, providing it not only with a beautiful setting, but also with easy access to fresh water for its bathhouse and other household necessities. However, what was a very convenient feature during its occupation, has become a complicated conservation challenge today.
Although the occupants of the London area have been changing the flow of the River for centuries, the ground water table remains high and our archaeological site, in turn, remains damp.
Water movement through the site brings with it a rich array of soluble salts. These travel through the remains of the Bath House, while they are dissolved in water, and crystallise whenever the environment gets drier (hence the term ‘soluble’ salts). These salts are slowly but surely causing a variety of damage, including delamination of the ceramic building materials and crumbling of the original mortar.
This is a complex conservation problem to solve , given that there is a ready supply of dissolved salt in the ground water and that it is not possible to achieve environmental conditions that could minimise evaporation of the water and crystallisation of the salts. One response has been to add ‘sacrificial sand’ to areas of the site around the archaeological remains. This acts to encourage groundwater to move through the sand instead of the archaeological remains, and thus reduce salt efflorescence on the actual structure. In spite of this, the salts nevertheless continue to appear on the archaeological remains. Although the salts are certainly a conservation problem in the long run, they also damage the public perception of the site as they give the impression that the Bath House is unloved and not well cared for.
Contesting this impression, students taking the Applied Heritage Management Master Class at the Institute of Archaeology work on the site every year to improve its accessibility, interpretation and condition.
The conservation part of this project this year focused on recording the distribution of salts and the damage they have caused. We mapped the general distribution of the salts, identified areas of damage on different materials and in different areas of the site, and also compared the concentration of this year’s salts with pictures taken during last year’s survey.
Our findings point to the need to increase the frequency of regular cleaning and removal of the salts. An annual cleaning would help reduce the presence of salts onsite, and mitigate future damage from the crystallisation of salts. This would be good for the long term stability of the Bath House, but would not remove the cause of damage, as ground water continues to move through the site, depositing the damaging salts. Improving the care of the Bath House will make it more interesting and enjoyable for visitors, and this may bring about better opportunities for funding for the long-term preservation of the Billingsgate Bath House. This is just one of many examples when conservation and public engagement work towards the same goal of making heritage more accessible to a wider audience, both for the benefit of the archaeology and the people interested in visiting or researching it.