When I sit down to enjoy a good book, there's something about the physical experience that can't be replaced. The weight of the book, the texture of the paper, the smell of the pages ... and apparently I'm not alone! In a 2023 survey, 30% of Americans purchased hard copies of books while only 20% bought digital books.
I was surprised to learn there is so much science involved in creating paper! The process starts when trees are harvested and stripped of their leaves and bark. The wood is chipped and pulped, then an acid is used to pull the cellulose from the plant cell walls, a main paper ingredient, out of the wood.
The plant cellulose is further processed through bleaching and treatment by baths of water and different chemicals. This helps the fibers bond together through hydrogen bonds - the same type of bonds that hold water molecules together to create surface tension! 💧 Additives are introduced to the mesh of drying paper to make it more durable.
Fun fact: older paper making techniques used cotton from clothing and linen as a starting ingredient. This is probably where the term "rag" used to describe a newspaper came from. 📰
How durable can a book be? That might be answered with the oldest book printed on some version of paper. The Nag Hammadi codices from Egypt take that distinguished title. The leather-bound papyrus books are 1,693 years old! 😱
Preserving paper is also serious business. The Nag Hammadi codices have been around for a staggeringly long time, but your average paper documents can't survive nearly that long. This is a problem as historical and invaluable books and documents continue to age.
Luckily, chemists have a pretty good handle on what contributes to the breakdown of paper: acid! Cellulose naturally acidifies over time. Environmental factors like high humidity and pollutants in the air can also drop the pH of paper documents. Acidic conditions cause the cellulose chains to become shorter.
There are a couple strategies used to preserve very old documents. One is keeping them in very controlled, air-tight conditions (if you've visited the Declaration of Independence, you know what I mean!). Second is a strategy of washing the paper in an alkaline solution. This is a painstakingly delicate process where the integrity of the ink and paper structure need to be accounted for.
Would you be surprised to read that not all paper is created equal? It's all about the length of those cellulose chains. Flimsy paper with a short life span, like the kind used to print newspapers, have short cellulose chains. In higher quality paper, a carbohydrate called lignin is removed from the mix. This helps longer, stronger chains of cellulose to bond together.
You could imagine that for really old books and documents, the cellulose chains must be pretty sturdy.
When it comes to fiber length, not all plants are created equal, either! Check out the following graph of the ranges of fiber length of a variety of plants:
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If I wanted to introduce this chart to my learners, here are some questions I'd have to go with it:
💡 What does the lower number of each rectangle mean on the graph? In this type of graph, the bars represent the lowest and highest ranges of fiber length for each plant.
💡 What makes cotton such a good material for paper? Check out the range for cotton and see how it differs from the others.
💡 What is the best tree for paper making based on this graph? Which tree has the longest fibers?
I hope you enjoyed the fun paper facts in this article. You might never look at a printed book the same way again!
- Chris
