The conservation of manuscripts and books is one of the most challenging issues in conservation science, because the organic biomolecule of cellulose is susceptible to rapid degradation as a result of the combination of several factors, both environmental and connected with the papermaking techniques that have been used since the end of the 19th century. Basically, paper undergoes degradation because it contains materials that catalyse degradation reactions.

The chapter focuses on some of these aspects and, in particular, discusses the role of acidity in the degradation processes. Within this conceptual framework, state-of-the-art methods for mass-deacidification, single-item treatment and application of anti-oxidants are discussed. The recent important contribution of nanotechnology to the development of innovative deacidification methods is then presented.