As the scaffolding on the Town Hall was lowered, some people have asked why the stone and brickwork building hasn’t been extensively cleaned. As with all elements of the project the historic nature of the building has dictated the appropriate and approved treatment.
In the past, historic masonry was frequently cleaned because cleaning was equated with improvement. However, experience has shown that inappropriate cleaning and coating treatments are a major cause of damage to historic buildings, resulting, in some cases, in irrevocable damage. Advice from English Heritage is that the cleaning of brickwork particularly, should be avoided wherever possible.
Abrasive blasting was popular in the early days of cleaning masonry because dramatic results could be achieved. However sand or grit blasting commonly tears or pits the surface of the brick, which will then soil and weather more rapidly. The fired face of the brick can also be removed by this method, rending the brickwork porous to rainwater.
On close inspection, the condition of the brickwork on the Town Hall was found to be good so cleaning was not advised. Built up dirt was more obvious on the lighter stone sections of the building and so it has been gently cleaned with water, which is generally agreed to be the safest method of cleaning.