Mad About Science: Paper

By Brenden Bobby
Reader Columnist

This is an article about the very thing you’re holding in your hands right now (unless you’re reading this online). Regardless, how meta is that?

Courtesy image.

We often take for granted the novelty of paper as an invention. It is designed to store a coded copy of the thoughts of a human mind for thousands of years while remaining lightweight and portable, yet something as trivial as a pinch of your fingers could easily destroy it.

The earliest known form of paper is papyrus, which was used in Egypt as early as the 4th century BCE. Papyrus paper was made from tissue of the papyrus plant’s stem called the pith. Early paper wasn’t layered in sheets like modern books, but instead rolled up into scrolls. This is actually the origin of the term “scrolling through your phone.”

It’s worth noting that just because the earliest example of paper dates from this era does not mean that paper didn’t exist before then. Due to the fragility of the material — and the suboptimal conditions in which it was likely kept during these periods of history — paper from before this time probably didn’t survive. This makes pinpointing an exact date for the invention difficult (if not impossible), much like other developments from antiquity like pottery and the wheel.

Papyrus was the nearest approximation to modern paper the western world would see for centuries. China developed a form of papermaking more closely related to contemporary paper, in which a number of fibrous plants were soaked and beaten into a pulp before being pressed together into a sheet. The process of creating paper was a closely guarded secret for centuries, until sometime during the 500s, when Buddhist monks in Japan replicated the process. Not long after, this form of papermaking began appearing throughout the Middle East and India as well.

It wasn’t until the 1600s that much of Europe began favoring paper made from plant fibers. Virtually all surviving medieval manuscripts from Europe were written on parchment, which is actually very thin animal hide treated with chemicals to hold ink. The Declaration of Independence and the U.S Constitution are both written on parchment, likely from a calf or goat.

The methods of paper creation haven’t changed that much in nearly two millennia, though the process has scaled up. Most of the process is now automated and designed to produce huge rolls of paper that are then cut into individual sheets. While the amount of paper that a manufacturer may have produced 1,400 years ago was likely a page or a large scroll, modern machines are designed to churn out giant rolls weighing 30,000 pounds or more. 

How many materials would be required to make a single roll of paper that large? You’d have to ask someone who works for a paper mill, because I couldn’t find that math anywhere.

The current process starts with the felling of a tree. Most modern paper is made from fibrous conifers like pines, firs and larches. The logs are thrown into a drum-like machine that tears the bark from the wood, then sends the bark away to be used somewhere else for things like bags of mulch or compost. The logs are then fed through a chipper that dumps literal tons of chips into massive piles that are then put into a vat to be chemically treated and turned into pulp.

Pulp is like proto-paper. This is a mass of lignin, the organic polymer that gives trees their woody texture. Lignin is a core part of what makes paper hold its form, as the chemical bath during pulping removes organic impurities and water from the lignin. After the chemical bath, the pulp is squirted into the first section of the papermaking machine — a mechanical beast that can be as long as nearly 400 feet in some factories. The pulp is squeezed between sets of huge stone rollers that spread and flatten the fibers into sheets. This is usually done several times before the paper sheet is put through a series of drying processes.

The drying process varies from mill to mill, though some employ a form of suction that pulls the water from the paper while others use a heated air treatment. In most cases, up to 90% of the water used and expended by the papermaking process is re-used in earlier stages.

Paper is bleached to get crisp, white paper that sharply contrasts black ink. This generally isn’t performed on newsprint, which is why you’ll notice some discoloration in newspapers. Office paper and paper destined for books is bleached with oxygen and hydrogen peroxide solutions to selectively whiten pigments without compromising the structural integrity of the paper.

After the bleaching process, the paper is ready to be cut into uniform sheets. Common practice at mills is to divide one large roll into multiple sizes depending on the customer’s demand, while wasting virtually zero of the paper in the process. Based on their customer’s needs, staff at the mill will run some calculations through a simple algorithm to divide the sheet up almost perfectly. A standard 8.5-inch-by-11-inch sheet of paper is often cut from the same roll as an 11-inch-by-17-inch sheet.

Sheets are divided and bundled together to be shipped to their customers. Most paper is eventually recycled, and ends up coming back to the mill to undergo the cycle all over again, mixed with other used paper to reconstitute its integrity. 

Specialty papers like photo paper are coated in chemicals to help them better retain colors with less ink bleed and also provide a glossy surface, but otherwise the process is virtually identical. This is true of paper destined to become cardboard, wax paper and tissue paper as well.

Curious about how the words get into the paper from there? I guess you’ll just have to recycle this issue and grab another one next week.

Stay curious, 7B.