Dictionary of Moisture Protection & Restoration

Cleaning (procedures and materials) The removal of all foreign matter from the stone, masonry unit and mortar. This is usually the first phase of a restoration or preservation project. It will establish the criteria of the colors and textures to match when repairing the damaged stones. Sometimes, contractors prefer to do the cleaning last. However, a mock-up should be performed first to establish the criteria. Cleaning is probably the most important phase and the most misunderstood procedure. More damage is done during the cleaning operation than any other phase of restoration. Too often the cleaning phase is rushed and destructive. Instead of starting with the gentlest type of cleaning, the contractor will often start with the most abrasive type and severely damage the stone. Cleaning methods should be only strong enough to do the required job and no more . When using cleaning products focus on the pH; this is the concentration of hydrogen ion in a solution. A small change in the pH value is a large change in concentration of hydrogen. Cleaning requires a good knowledge of the stones. Quartz stones have a greater resistance to acids and high alkaline detergents. Granite, which is primarily quartz, will take aggressive cleaning without damaging the stone; limestone will not tolerate any cleaning agent because of its calcium content. When using detergents, poultices and diluted acids solutions, watch the pH.

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