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Preventative Conservation

 

 

It was becoming evident that by-products of deterioration produced as paper, film and other organic materials aged, played a prominent role in deterioration, as did harmful oxidative and acidic molecules found in the environment surrounding archival collections. People understood that pollutant molecules such as ozone, sulfur dioxide, and oxides of nitrogen could damage their collections. These pollutants also damage buildings, statues and even living ecosystems. However, until recently, most people generally did not realize that indoor pollutant levels could be quite high. {Indoor pollutants are present in much higher concentration than those found outdoors, and can be significantly more harmful to artifacts than typical open-air pollution We were seeing damage from pollutants occur even in a controlled museum environment. 3} Indeed these compounds can even be produced indoors by a variety of materials and furnishings, as well as by heating equipment and various appliances. Deleterious pollutants and chemicals produced inside include deteriorative agents such as formaldehyde, peroxides, formic acid, and acetic acid, which can be emitted by wood, plywood, particle board and chipboard. Protein-based glues and wool can yield sulfides. Fumes from an underground parking area can cause elevated interior levels of oxides of nitrogen, and sunlight entering a building can be responsible for increased photolytic reaction rates, resulting in concentrations of oxidative and acidic molecules such as ozone, peroxides, nitric acid and other nitrogen-containing molecules which are present at higher levels inside than outdoors. Acids and other harmful molecules also migrate from adjacent acidic materials. Because the artifacts we save degrade over time and produce by-products of deterioration, and because they are generally housed together in high density storage areas, harmful compounds tend to accumulate in higher concentrations within the storage area.

 

Another common misconception used to be that the alkaline buffering in archival papers and boards dealt effectively with these deleterious compounds. Conservation scientists now realize it is important to understand that the protection conferred by alkaline buffering does have limitations. If an acid migrates to, or arises from within ( in the form of a by-product of deterioration), or forms from a pollutant coming into an alkaline buffered paper, and if this acid is in contact with a particle of alkaline buffer, the acid will be neutralized. However highly reactive oxidative gases such as ozone and peroxides are not acids, and pollutants such as sulfur dioxide and oxides of nitrogen do not become sulfuric or nitric acid until they combine with oxygen and water to form these acids. Dr. Charles Guttman and his team from the U.S. National Bureau of Standards published important research (Protection of archival materials from pollutants: diffusion of sulfur dioxide through boxboard, Journal of the American Institute for Conservation 32: (1993) 81 - 92) showing how readily pollutant molecules pass through alkaline buffered boards. Obviously severe damage to a collection can occur when these harmful molecules pass through an archival paper or board, unaffected by the alkaline buffer, and react with or form acids on the artifact housed within the archival container.

 

3. From an interview with James Druzik, Senior Scientist, the Getty Conservation Institute, printed in the October 2003 Decor magazine.