Exposure to light typically gets most of the blame for fading photographs. However, air pollution can sometimes be an even bigger cause.
The inks, pigments, and metals used in photography can chemically react with air pollutants and degrade images, even in the absence of sunlight. This is not a big problem in modern cases since the process is slow and the original digital photograph can just be reprinted. However, it’s not that simple when it comes to historic photographs with only one original copy. Protection from air pollution is something that needs to be considered to preserve them.
Ozone is one of the most damaging pollutants to photographs. Ozone is made by a photochemical reaction between nitrogen oxides (NOx) and volatile organic compounds (VOC), both of which can be released by burning fossil fuels.
Ozone is a highly reactive gas that can interact with and damage many different substances, including those used in a wide variety of print types.
For example, “gelatin silver” prints (most 20th-century black-and-white photographs) degrade in a way known as “silver mirroring.” The silver in the images can react with ozone, and other pollutants, causing a sheen to develop on the surface of the image.
Nitrogen oxides, and even indoor fumes from solvents and paint, can have the same effect. Dry deposition of acids can make the paper more brittle and cause other types of prints to fade in different ways.
The effect of pollution on photographs is cumulative, so even low concentrations can be damaging if exposure is long-term. Warm and humid conditions also worsen this process by speeding up the chemical reactions at the root of the degradation.
The Library of Congress (LOC) recommends storing photographs in an area with humidity and temperatures as low as possible for this reason. The LOC also suggests filtering incoming air, ensuring good air circulation, and avoiding drafts of unfiltered air from outside.
Storing photographs in airtight sleeves or boxes can also help. While this advice may be most important for institutions with historical collections, it also applies to anyone with old family pictures or modern inkjet prints they plan on preserving for a long time.
In addition to protecting your photographs, learn what you can do to limit air pollution. Follow NYS open burning regulations and avoid products with unhealthy fumes to help protect your health and your photographs.
Photo of a 100+ year old gelatin silver print, seen in two different angles of light, displaying silver mirroring provided.
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