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.