Mass deacidification is a term used in library and information science as one possible measure against the degradation of paper in old books, the so-called "slow fires". The goal of the process is to increase the pH of acidic paper. Although acid-free paper has become more common, a large body of acidic paper still exists in books made after the 1850s; this is because of its cheaper and simpler production methods. Acidic paper, especially when exposed to light, air pollution, or high relative humidity, yellows and becomes brittle over time.[1] During mass deacidification an alkaline agent is deposited in the paper to neutralize existing acid and prevent further decay.[2] Mass deacidification is intended for objects on acidic paper that will be lost if no action is performed.