Stone Cleaning at GraniteForYou.com

• Stone cleaning
• Principal cleaning methods
• Published Guidelines
• Industry Reaction
• Stone cleaning Conclusions

Principal cleaning methods

The principal cleaning methods used

Two fundamental methods of cleaning buildings have habitually been adopted, although a number of specialised techniques have become available in recent years:

Physical methods: these include brushing and rubbing, washing and steaming, wet and dry abrasives, or surface redressing.

Chemical methods: applied as liquids or poultices, these may employ the use of alkaline treatments, acidic treatments or organic solvents, singly or in combination.

Special techniques may promote the use of impregnated sponge, laser technology, ultrasonic equipment, heat lances, gypsum inversion, bacteria, poultices or gels, and surfactants (degreasants or soaps).

Not all treatments are appropriate for all materials, and extreme care needs to be exercised when deciding which system to adopt. Due to the need to minimise the risk of damage, the 'do not clean option' should also be borne in mind.

Measures to be adopted to minimise risk where cleaning is acceptable in principle

Determining the actual testing methodology, and the validity of trial area results, can be an elaborate process if it is to be carried out effectively and meaningfully. Topics that should be considered include colour measurements, depth profiling, surface roughness tests, and the use of scanning electron microscopy, determining the petrology (the geological structure of the stone) and pH values, porosity and permeability measurements, before and after test cleaning. Care needs to be exercised when contemplating the consequences of washing chemicals into underlying masonry during rinse-off stages, and the question of how to stop 'wash-in' occurring on porous stone surfaces when 'washing off' chemicals should also be addressed.

Reporting and recording the consequences of tests should lead to a full analysis of results before writing a relevant specification and obtaining statutory consents (if required). Risks may also be reduced by carefully selecting an experienced and suitable contractor; by determining the training and experience of site operatives; by ensuring effective site controls and health and safety precautions; and by the maintenance of adequate site progress records.