Paper and papermaking
by Chris Woodford. Last updated: March 9, 2021.
If you weren't glued to your computer screen right now, you might be reading this article on paper from a book; for about 2000 years until the appearance of the World Wide Web, virtually all written information was distributed in printed form. The idea of getting information from inked-up sheets of paper is starting to seem a little bit old-fashioned, but that doesn't mean we're going to ditch paper anytime soon. People have been predicting the arrival of the "paperless society" for decades and it still seems no nearer; if anything, we use more paper now than ever before—and not just for printing. Huge amounts of paper and card are still used for product packaging, in towels and diapers, and in a wide variety of building materials. It's probably no exaggeration to say that paper is the world's favorite material. Let's take a closer look and what it is and how it's made!
Photo: Even in the computer age, we still use vast quantities of paper. This photo could have been taken yesterday; in fact, it was shot in 1943 at the huge Southland Paper Mills near Lufkin, Texas, and shows newsprint (paper for printing newspapers) made from wood pulp using the Kraft process. Photo by John Vachon for the Office of War Information, courtesy of US Library of Congress.
What is paper?
Paper is a dried, compressed mat of plant fibers—nothing more, nothing less. It's a bit like clothing you can write on. No, really! Clothes are made by weaving together yarns such as cotton and wool spun from natural fibers. Paper is more like the fabric we call felt, made without the weaving stage by pressing together cellulose fibers extracted from plants and trees so they knit and fuse to form a strong, solid, but still very flexible mat.
How is paper made?
Most paper pulp is made from trees (mainly fast-growing, evergreen conifers), though it can also be made from bamboo, cotton, hemp, jute, and a wide range of other plant materials. Smooth papers used for magazines or packaging often have materials such as china clay added so they print with a more colorful, glossy finish.
Photo: Paper can be made from lots of different materials. 1) Trees felled for papermaking. Although many different tree species can be used, hardwoods provide the bulk of the fibers in paper, while softwood fibers are used more for strength. 2) Stacks of hay waiting to be made into low-grade paper in Hebei Province, China. China and the United States are the world's leading paper makers, each producing close to 80 million tons of paper per year. Photo by Simon Tsuo courtesy of US DOE/NREL (US Department of Energy/National Renewable Energy Laboratory).
Here's the basic idea: you take a plant, bash it about to release the fibers, and mix it with water to get a soggy suspension of fibers called pulp (or stock). Then spread the pulp out on a wire mesh so the fibers knit and bond together, squeeze the water away, dry out your pulp, and what you've got is paper!
Paper is really easy to make by hand (try it for yourself) but people use so much of it that most is now made by giant machines. Whichever method is used, there are essentially two stages: getting the pulp ready and then forming it and drying it into finished sheets or rolls.
Chart: Recycled paper (green line) has now overtaken woodpulp (brown line) as the main source of raw materials. In Europe (EU plus Norway and Switzerland), about 72 percent of paper was recycled in 2019, compared to just 40 percent in 1991. Even so, very large amounts of wood are still consumed to make paper: roughly 154 million cubic meters of wood are used by the European paper industry each year (28 percent hardwood and 72 percent softwood), but only about 40 million cubic meters of that (less than a third) finds its way into papermills as usable pulp. Chart based on statistics from Key Statistics: European Pulp and Paper Industry 2019, Confederation of European Paper Industries (CEPI), 2020.
Papermaking by hand
The raw plant material is placed in a large vessel filled with water and literally beaten to a pulp to make a thick suspension of fibers called half-stuff. This is formed into sheets of paper using a very basic frame made of two parts: a metal mesh called a mold that sits inside a wooden frame known as a deckle (a bit like a picture frame). The mold and deckle are dipped into the half stuff and gently agitated so an even coating forms on top, with most of the water (and some of the pulp) draining through. The deckle is then removed from the mold and the soggy mat of paper is placed on a sheet of felt. This process is repeated to make a number of interleaved sheets of paper and felt, which are then placed inside a screw-operated press and squeezed under immense pressure to squash out virtually all the remaining water. After that, the sheets of paper are taken out and hung up to dry.
Photo: Look really closely at almost any ordinary paper and you'll see just how fibrous it is! The photo on the right is a closeup of the one on the left. It might look like a pile of folded fluffy bathroom towels, but really it's sheets of paper! This is 100 percent recycled Evolve paper made by M-real.