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. The Association for Gravestone Studies - FAQ Page 6 of 13 <br />(liquids and powders) are not recommended for cleaning <br />masonry. They are rendered insoluble by calcium ions <br />present in stone and hard water. They may also produce <br />free alkali and fatty acid salts. <br />2. Non-ionic Detergents (e.g., Photo Flo - a Kodak <br />product): Non-ionic detergents are recommended for <br />cleaning gravestones. They are electrically neutral cleaning <br />agents that do not contain or contribute to the formation of <br />soluble salts. They provide better wetting of the masonry <br />surface and, therefore, successfully facilitate the removal of <br />general soiling. Non-ionic detergents are available from <br />conservation, janitorial, and photographic suppliers. A <br />suggested cleaning solution is one ounce non-ionic <br />detergent to 5 gallons water. <br />B. Acidic Cleaning Materials <br />1. Hydrochloric or Muriatic Acid, Phosphoric Acid (e.g. "Lime Away," <br />'Naval Jelly"), oxalic acid are not recommended for general cleaning of <br />gravestones. The use of hydrochloric or muriatic acid may result in ferrous <br />chloride (rust) staining and the deposition of soluble salts. Muriatic acid, <br />which is readily available in hardware stores, is a raw acid. It is a by- <br />product of processing steel and contains metallic particles that can cause <br />ferrous staining. <br />C. Alkaline, Corrosive, and Biocidal Cleaning Materials <br />1. Sodium Hydroxide (e.g., "Borax"), Sodium Hypochlorite (e.g., "Clorox" <br />"liquid chlorine") is not recommended for general cleaning of stone. <br />2. Calcium Hypochlorite (e.g., Chlorine, "HTH," "Shock Treatment"): <br />Calcium hypochlorite or chlorine is effective for the removal of biological <br />growth. It is a granular product that is not to be confused with "liquid <br />chlorine" or sodium hypochlorite. Calcium hypochlorite is available from <br />swimming pool suppliers. A suggested cleaning solution is one ounce <br />calcium hypochlorite to one gallon hot water. This product should be used <br />only when a waterhose with a good water pressure (e.g., 55 psi) is <br />available. <br />3. Ammonium Hydroxide (e.g., household ammonia): Solutions of <br />household ammonia are recommended for cleaning light colored stones. <br />Ammonia is particularly effective for the removal of biological growth. <br />One cup ammonia to one gallon water. <br />4. Quaternary Ammoniums (e.g., algaecides or biocides for swimming <br />pools): Quaternary Ammoniums have a slightly different chemical <br />structure than ammonium hydroxide. They are especially effective for the <br />removal of biological growth, particularly stubborn black algae. <br />Quaternary ammoniums are available from swimming pool suppliers and <br />list ingredients such as alkylbenzyl trimethyI ammonium, benzyl alkyl <br />dimethyl ammonium chlorides, or benzyl aklyl dimethyl ammonium <br />bromides. <br />5. Trisodium Phosphate (e.g., "TSP, "Calgon"): Trisodium phosphate is <br />not recommended for cleaning monuments. It can cause the formation and <br />deposition of soluble salts. "Calgon" contains trisodium phosphate and a <br />number of additives that may be detrimental to monuments. <br />http://www.gravestonestudies.org/faq.htm 3/12/04 <br />