Due to the variable nature of stone and its response to the environment means that a standard approach to cleaning is not possible. As a result cleaning and repair of buildings is a specialist procedure.
Before we list the methods of cleaning, we use. We would always recommend carrying out a full survey and test sample to establish the best method of cleaning as there will be a huge variance in cost between these methods.
These are just some of the methods we can use when cleaning a property.
STONE MASON CLEAN
Clean mains-pressure water provides a nebulas mist spray to loosen the dirt, which enables handheld soft brushes to agitate and clean the surface.
DOFF (Thermatech ®) SYSTEM
Involves superheated hot water, or steam that is for general cleaning of masonry surfaces. However, this can also be used for the removal of paint and algae.
Chemical based gels are used to cover areas of localised staining such as tar, to loosen and break down its resistance to cleaning. This process is usually backed-up with the use of other methods such as DOFF.
WET VORTEX MILD ABRASION (also referred to as JOS)
Projects a low-pressured air and finely powdered calcite through a special TORC nozzle, which gently wears away pollutants, in particular, carbon.
Incorporates solvents, chemical based acids and alkaline to remove staining, it is best suited to terracotta, sandstone, granites and heavily soiled brickwork.
However, this method is not favoured in conservation works to listed buildings and not recommended by advisory bodies and conservation architects. However, on occasions when authorised, using specialists and masonry cleaning chemicals, this method can be used.
N.B.: Please note it is important with this method to allow for scaffold access and the work area must be fully sheeted, allowance for water must have run-off and collection measures.
Is used when a high degree of control is required, used on sensitive materials and is ideal for statues. However, this is a painstakingly slow process and, therefore, can prove to be an expensive option.