Paper quality depends on the properties of the cellulose fibers and the sizing of the paper for receiving ink and related materials. Animal glue was used originally; it was replaced by resinous glue around 1806. This treatment necessitates the use of alum to bind the resin to the fibers. Alum as a sulfate contributes to fiber decay. Consequently, other materials have been selected to replace alum and it is now possible to manufacture papers which are neutral and remain neutral in the presence of heavy air pollution. The proper restoration, storage, and exhibition of prints and drawings calls for such paper.