The conservation treatment of stone sculpture and architectural stone.
From ancient roman marble heads, architectural details and fireplaces to contemporary sculpture the task of conserving and restoring stone is diverse.
As conservators we try to understand how change to a material or object occurs and how it can be slowed down or its effects reversed. Conservation treatment involves change for the sculpture or stonework and so we are always aware of the long term implications of action taken in statue or sculpture conservation.
Stone restoration and conservation demand the individual condition and requirements of each project to be taken into consideration. Whether it is sculpture repair or restoration or architectural stonework treatment, the process in each case relies on a detailed understanding of each stone type and follows a process of inspection, testing, preparing, cleaning and restoration.
In the example of architectural stone, atmospheric conditions will often have the largest part to play in their need for attention.
The build up of sulfate deposits can form a black crust on the surface which will inhibit the stone’s ability to breathe. When water becomes trapped under this crust the expansive forces of freeze thaw cycles can result in damage to the stone. The trapped water can also contribute to the crystallization of soluble salts already in the stone resulting in more deterioration.
Cleaning these deposits along with the build up of dirt, organic matter and staining are therefore often our main concerns when treating outdoor stonework.
Our principle is to preserve the stone as much as possible therefore prioritising the use of non abrasive, non aggressive cleaning methods; this often involves the application of a poultice which softens the unwanted material making it more easily removable manually. A Doff steam cleaner can also be used for large areas of resilient dirt on harder stone.
Any stone repairs we apply to either damaged sculpture or stonework are of a softer nature to the intrinsic stone, this allows them to act in a sacrificial nature when the stone expands and contracts under different environmental conditions.