Historic Churches 2021

28 BCD SPECIAL REPORT ON HISTORIC CHURCHES 28 TH ANNUAL EDITION Houses of Parliament using infra-red photography. Although Adrian was in post at Cologne University, he and two colleagues agreed to carry out imaging studies on The Last Judgement , so long as secure access could be provided. Following consultation with the parish, and architect (Antony Feltham- King), arrangements were made to erect a secure, fixed scaffolding so that all areas of the wall painting could be studied. The platform had to be particularly stable for the imaging techniques proposed. Each of Gillian’s terahertz scans took around 40 mins to complete. The slightest vibration would ruin the result, so we all had to vacate the scaffold. Adrian used an Osiris infra-red camera, which took images at a wavelength of 1700nm (1.7 microns) and was much less sensitive to vibration. Evidence of medieval paint under the 19th century repaint, was detected by both Gillian’s and Adrian’s teams; and the best results are shown here. With a full scaffold the entire surface of the wall painting could be studied at close quarters. In terms of the future for the painting, the most significant finding from this and the previous survey was the extent of detached painted plaster. In places this was pronounced, and in some areas there was risk of imminent loss. Treatment trials were carried out; these included securing detached painted plaster, securing paint flaking, and cleaning. Scaffold access enabled Antony Feltham-King and the structural engineer, Andrew Waring, to consider larger structural issues. THE CONSERVATION PROGRAMME In 2019 the programme of conservation largely focused on securing detached painted plaster, replacing earlier loose plaster repairs, and cleaning; with some time spent securing areas of paint flaking. Areas of detached painted plaster were secured by injecting either lime slurry or lime grout into voids behind the painted plaster. Once the slurry or grout was introduced a spring- loaded press was positioned to hold the treated section of painted plaster in position while the slurry/grout cured. Cleaning was undertaken in three stages. Firstly, loosely adhering dirt and dust were removed using soft artist’s brushes, directing the unwanted dirt and dust into the nozzle of a vacuum cleaner. This operation was also valuable because it meant the entire surface of the wall painting could be closely observed in a methodical manner. Instances of paint flaking were consolidated. For the second stage, more stubborn surface dirt was removed using small damp sponges. The visual improvement from this alone was apparent. The final stage involved the use of a chelating agent applied as a gel by brush. Residue from this operation, both dirt and chelating agent, was removed using cotton wool swabs dipped in de-ionised water. The improvement in the appearance of the wall painting from this stage was marked. Another factor which enhanced the appearance of the wall painting was the removal of an iron tie bar, set horizontally across the middle of the wall painting. When the idea of removing the iron tie was first considered, it was decided not to in case this lead to structural damage. However, during the course of the work, loose cement mortar was removed where the tie bar pierced the south wall, revealing that the tie bar had rusted through and was no longer functioning as intended. Following consultation with the architect and structural engineer permission was given to remove the tie bar. As a result of cleaning, traces of the medieval painting can be seen in the top third of the painting under the 19th century repaint. Analysis of paint samples from The Last Judgement , taken during treatment, showed that there is another paint layer below this one, indicating that there was at least one earlier medieval scheme. As one moves down the painting, evidence of more than one overpainting becomes increasingly apparent, with the greatest amount of overpaint in the lowest third of the wall painting. Unexpected passages of medieval painting were found at the very bottom of the wall painting, and on the wall immediately below it. More than one layer of medieval paint was identified and some of what we found remains on view; the rest has been painted out using reversible paint. It is worth taking binoculars when visiting St Thomas’s, so that you can see these passages clearly. The second component of the programme of conservation concerned the walls of bays one and two of the nave. This aspect proved to be more rewarding than anticipated because the result achieved from cleaning the ashlar was much better than originally hoped for, and some particularly interesting findings were made. The most significant of these was that the shields on the capitals at clerestory level, six on each side of the nave, are painted with merchant’s marks. When the wall painting was created, in the late middle-ages, Salisbury was the sixth largest city in England, and St Thomas’s attracted financial support from wealthy merchants. The marks are a permanent reminder of those who invested in the building of the church. Another discovery was medieval paint on the engaged columns above the capitals. It is possible that the paint, a field of black with a bright border in Peter Martindale consolidating areas of detached plaster: the metal bars which hold the pads in place are supported off the scaffolding Joanna Pucci cleaning the surface with a chelating agent applied as a gel by brush. Residue from this operation, both dirt and chelating agent, was removed using cotton wool swabs dipped in de-ionised water.