The Garrick Club (named after the 18th Century actor David Garrick) was founded in 1831 by a group of literary gentlemen to promote relationships between artists and patrons. Built in 1864, the Garrick Club had never been cleaned and was covered in a black sulphated crust, once common to all Victorian buildings of London. The decision to clean it proved to be fairly controversial because its grimy facade was of historical interest and had become famous among architects, aesthetes and Londoners in general. However, the sulphated crusts had become so thick that it had started to cause the lime render to delaminate and fall onto the busy Covent Garden street below. This determined that it was time something was done. In 2005, a major restoration project was undertaken in agreement with the Garrick Club’s House Committee with full support of English Heritage.
Plowden & Smith were commissioned to undertake conservation cleaning trials and to create a method statement and specifications for cleaning the facade. Removing the sulphated crust and the general build-up of dirt was not straight forward, as analysis indicated that soiling was generally about 2mm thick and the gypsum cruel 0.5mm thick. The rendered surface had been applied in several layers and the bonds between the layers were potential weak spots that could fail if excessive amounts of water were used for cleaning.
The sulphate crust forms either an insoluble or partially soluble layer and common cleaning methods include high pressure water systems, such as JOS (a low pressure vortex process using a mixture of air, fine inert powder and water) and DOFF (which uses a combination of pressure washing and high temperatures). However, these methods were not very effective or efficient on their own due to the high level of soiling and patchy cleaning results. In addition, the large amount of water required risked delamination of the render and when water is left to trickle down the surface of a building it can become stained, which is nearly impossible to remove at a later date.
Cleaning trials identified that a poulticing technique commonly used in ceramic and sculpture conservation could be successfully used for cleaning the building. Gels made from Laponite RD and water were particularly efficient at maximising water contact with the building’s surface without causing saturation of the structure or substrate, which therefore minimised risk to the original surface. Furthermore, there were no health and safety risks for staff, the public or the environment and in fact Laponite RD is commonly used in food manufacture.
Poulticing methods were combined with the more conventional methods of cleaning. The DOFF system was used to wash the whole building down, removing loose surface dirt and debris and to pre-wet the surface. The JOS system was used to selectively remove stubborn, thicker areas of crust. Where the sulphated crust exceeded 20mm, manual cleaning had to be employed using chisels until the crust was thin enough to finish the cleaning with the JOS system.
When the surface was still damp the Laponite RD was applied and immediately covered in cling film. This was left on for several days before being washed off. This resulted in the complete removal of the black sulphation and revealed the original straw colour of the render.
The combination of the JOS, DOFF and Laponite RD cleaning methods proved to be highly controllable and effective. The surface finish was even and retained a patination consistent with its age. We were careful not to over clean the sculptural details such as the scrolls and swags; if they were over cleaned the swags would look flat and washed out from ground level, losing their sculptural impact. This methodology matched the original brief, which was to achieve a sympathetic rather than a severe clean.
