Q. Why does old newspaper become discolored faster than other paper?

A. The raw material of paper is cellulose contained in wood pulp. Paper is made by dispersing cellulose in water, filtering it, drying it and forming a sheet on a plate.

For example, the raw material of Japanese paper is cellulose from trees such as the mulberry. It makes strong paper and is used for paper money.

The paper used for newspapers is foreign paper and its raw material is the pulp of different trees. That pulp contains lignin in addition to cellulose. About 20 to 30% of lignin is contained in dried wood and it plays a role in reinforcing the cells of plants and at the same time binds cellulose. While paper made of pulp without lignin do not discolor easily, newspapers which use a massive amount of pulp with lignin discolor more readily.