Masonry Magazine August 2001 Page. 15
While abrasive injection systems are gentler than the sand, shell and cob methods, they are still abrasive and not accepted for restoration of registered historic landmarks or structures being considered for listing. A major problem is that these new camouflaged sandblasting systems are being sold as chemical-free and causing a resurgence of these archaic systems. "Chemicals" has become a negatively-charged word, but, in restoration, its application can be most beneficial.
The chemical method involves different proprietary formulations for individual substrates. Only those chemical manufacturers, whose formulations and technical expertise have been shown to be continually proven effective, should be considered.
Most clay masonry requires a proprietary mild blend of inhibited acid ingredients with a biodegradable surfactant detergent to suspend and remove the carbon, soot and pollution. Building owners and architects are to be warned of contractor's "sidewalk moonshine mixes," raw acids, lye flakes, and jobsite concoctions that give chemical cleaning a bad name and damage the concept and reputation of professionally manufactured/blended products. The professional products are diluted with water to the best ratio that will effectively clean the surface. The dilution rate is determined by doing test sample cleaning areas. Test, pre-cleaning, demonstration areas are mandatory prior to any responsible type of chemical cleaning project. Testing on any type of surface is conducted by choosing areas that are most indicative of the soiling condition on the structure.
Many buildings incorporate different types of building materials in their construction. Each individual masonry type must be tested and the same equipment that would be used during fullscale operation must be used for the test. For example, don't use a garden hose to wash a test area if a pressure washer will be used during full-scale operation.
Building owners and architects are to be warned of contractor's "sidewalk moonshine mixes," raw acids, lye flakes, and jobsite concoctions that give chemical cleaning a bad name.
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The Differences The Cut
MASONRY AUGUST, 2001 15