We all have noticed that newspapers turn yellow after a few days if we leave them aside. But also interesting newspaper clippings that we keep in folders turn yellow after a while. Why does paper turn yellow with time?
Hardly any other invention in human history has had such an immense influence on the development of society as that of paper. Formerly a luxury item, it has now become a cheap mass product albeit with a finite shelf life. The reason for this is the components of wood that have been in the paper since the middle of the 19th century.
We first wrote on parchment made from animal skins and before 1850 on hand-made paper, which consisted of shredded cotton rags and was referred to as rags. The paper industry now used cheaper raw material wood to extract the cellulose.
To obtain pure, stable cellulose from wood, the raw material has to be broken down through a complex chemical process. The product is so-called wood-free papers that hardly turn yellow. Paper production became much easier with the invention of mechanical wood pulping, in which finely ground wood is processed directly into paper.
But the cheaper variant of papermaking has its downsides. Since the wood pulp paper contains all the components of the wood, this paper reacts with light. Just as a wooden board darkens in sunlight, the paper that is exposed to daylight has a yellow tinge. A substance called lignin, which is contained in wood, is responsible for this.
Paper Destroys Itself – What causes the paper to yellow?
But that’s not all. Paper made from cellulose has to be strengthened to make it writable. For this purpose, substances containing aluminum sulfate are used as glue. In turn, acids are formed from this. These split the cellulose chains in the paper into smaller pieces. The paper loses its strength and becomes brittle. The massive breakdown of cellulose ultimately leads to paper disintegration. The self-destruction of paper affects virtually all writings and books that were produced after 1850. For archives and libraries, paper crumbling is a ticking time bomb, because restorers can only save a few fonts with great effort.
But paper disintegration is also an issue for household use. Interesting newspaper clippings, as well as anniversary edition books or documents, are not immune from this. And even your favorite book becomes unsightly and porous at some point. Particularly cherished or important pieces can be packed in acid-free paper sleeves but never in PVC film. And, above all, stored in a cool, dry, and dark place. This cannot stop the paper from falling apart, but it can slow it down considerably.
With today’s most popular way of quickly doing a scan, the question arises again as to which storage medium is the most suitable and, above all, the most durable. There is also the option of copying really important things onto acid-free paper and keeping them as light-protected as possible.
Good to know: In the paper industry, a rough distinction is made between paper, cardboard, and cardboard. Because of the many possible combinations of raw materials, production, processing, and use, a distinction is now made between 3000 different types of paper.