The most harmful contaminant in the atmosphere is sulphur dioxide, a gas produced by the combustion of fossil fuels. Sulphur dioxide is absorbed by the paper and converted into sulfuric acid. This acid causes discoloration, brittleness and eventual disintegration of the paper fibers. Most damage to paper is caused by improper handling, storage, and display methods. Poor handling causes tears and stains left from dirty, oily hands.
People often attempt to repair tears with pressure sensitive tapes or glues.
These adhesives migrate into the paper causing irreversible stains and are very difficult to remove. Prints and important documents are often stored rolled up or in boxes made of highly acidic cardboard or wood. In addition they are typically stored in either the attic or the basement with high levels of temperature and humidity. Unfortunately, improper framing with acidic matboards and plain picture glass actually speeds deterioration instead of providing protection. Pictures that have been kept in a frame containing wood-pulp matboard for just a few years begin to show a characteristic brown stain that corresponds with the inner edge of the mat opening.