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Monument Preservation 101: Cleaning Masonry

By Dustin Hornsby
Cleaning tombstones and markers is a crucial part of preservation. However, many common cleaners can severely damage masonry.
Household bleach or other oxidizing cleaners may chemically react with the surface and leave soluble salts in the pores.  The damaging effects of soluble salts are intimately linked with the wetting and drying cycles of the masonry.
All masonry is porous. Water, chemicals, and other minerals can seep into the stone through its pores. The salts created form the chemical reaction will dissolve in water and be carried inside through these microscopic channels.  When the masonry dries, the water evaporates, and the salts crystallize.


The fine pores cannot accommodate the increasing accumulation of salts and are eventually broken apart by the expansive forces of the crystal growth, causing the surface to decay.
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Environmental and mechanical concerns, such as the type of masonry, should be taken into consideration when determining a cleaning regimen for a marker. The method and frequency of cleaning should be determined by a professional.


Feel free to contact the restoration staff at Historic Oakland Foundation if you have any questions;

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