A combination of airborne particles and the constant wetting and drying cycles all contribute to cause contamination near the surface of the stonework. This is often referred to as surface soiling and may not necessarily occur in a uniform manner across the entire surface of a building. This can result in the accelerated decay of the underlying surfaces and the need for extensive stone replacement, which can be a very invasive and expensive process. Whilst this process takes many decades, the removal of surface soiling on stonework is often desirable to prevent these much more serious problems from occurring in the future.
Historic Property Restoration Ltd is trained and well versed in the many stone cleaning techniques.
Intermittent Pulse Washing
A simple method particularly suited to limestones and marbles where the surface deposits are often soluble in water. Pulse washing allows the surface deposits to be gradually softened to a point where they can be removed by simple brushing.
This method is so effective that light surface tooling evident on the face of the stonework can be retained whilst the soiling is removed.
Low Pressure Micro Air
This system has been successfully used on some of our most prestigious buildings, such as scheduled ancient monuments. The flexibility of this system allows even the most ornately carved stone features to be cleaned without damage, leaving the tooling and surface patina intact.
Neutral Detergent Chemical
The use of high acidic chemicals in the past has left the industry very guarded when considering the use of chemical cleaning methods, as acid-based cleaners can dissolve the binders within calcareous sandstones. However, technological advances and a much greater understanding of the effects of chemicals on the stone matrix mean that in certain circumstances chemical cleaning can be an effective solution. Engaging a suitably qualifi ed contractor, and carrying out test panels as part of a pre-contract exercise is essential.
Particularly suited for use on heavily stained stone. The various chemicals are mixed to form a jelly, which is thinly applied to the stonework and then covered to prevent drying out. The poultice is removed after 24hrs and re-application carried out as necessary until the desired result is achieved. Alternative methods should be considered for more porous sandstones and limestones.
Testing, analysis, and sample panels are an absolutely fundamental part of the selection of an appropriate stone cleaning technique. Historic Property Restoration Ltd carries out this preliminary investigation work as an integral part of our stone cleaning service.