Paper Basics

(a short pedantic tutorial)


Paper is so inexpensive and ubiquitous, that most of us give it little thought, paying more attention to the message on the paper or what's wrapped inside it, than to the paper itself. In our "disposable society" paper is one of our most disposable items.

However..........

Up until the mid-1800's paper was a relatively expensive commodity and was available only in individual hand-made sheets. Paper was pretty much limited to the size of a paper making frame that could be handled by one or two people. There were two problems; the ability to manufacture in high volume and the source of raw material.

Rags were used exclusively for high quality paper; various other materials (e.g. grass & straw) found their way into lower grade papers such as cardboard or wall coverings. With the rapid industrial growth of the 1800's the use of paper grew rapidly, and the supply of raw material simply did not keep pace. This became particularly acute during the US civil war when saving rags was viewed as a patriotic duty, (much as at least some of us(?) can remember saving tin cans and paper during WWII.)

The economics changed rather abruptly when a satisfactory method was developed for manufacturing paper pulp from wood and the paper-making machine (popularly called the Fourdrinier machine) was invented. The price of raw materials dropped and paper was for the first time available in long rolls. Both events happened at just about mid-19th century. (e.g. the first wood pulp mill in the US was constructed in 1863 near Philadelphia.)

In its purest form, paper is an amazingly simple and natural material, although it has a rather brutal beginning. A material such as linen, cotton, or chemically treated wood chips is reduced into almost pure cellulose fiber. In the mechanical pulping process the fibers are mashed, flattened, and fibrillated in a water slurry, the process being appropriately described as "beating". The result is a liquid pulp with is supplied wet to the paper-maker or dried in sheets to be reconstituted for later use.

To form a sheet of paper, the slurry of pulp is deposited on a screen, (in a hand-held fame with deckle or on a continuous belt as in the modern Fourdrinier machine), and the water allowed to drain off. Further pressing of the sheet removes water and encourages a weak chemical bonding between the cellulose fibers. Thus, satisfactory paper can be made by a process that is ancient and remarkably simple.

Modern commercial papers are significantly different from those of the 1800's. First, wood pulp has become the dominant raw material. Wood fibers tend to be shorter than those in linen or "rag" papers. Thus a wood-based paper has significantly different physical characteristics than a linen paper. (Hence some of the differences between the paper used in currency and that used in our daily newspaper.) An 1800's manila paper, used in paper rowing shells, would have actually contained a large portion of very long manila hemp fibers. (Modern "manila" paper retains the name alone to describe an appearance, not fiber content.)

In addition, extensive use is now made of additives for the treatment of paper and pulp during manufacture. Thus while "wet strength" would generally be accepted as a positive property for many papers, 19th century boat builders used their paper's natural "wet weakness" to allow them to form it over the complex curves of boat molds and coped with waterproofing the paper after the hull was built. Our suspicion is that high-tech "papers" or paper substitutes, like duPont's Tyvek, would be difficult to form over a mold, but we are willing to be proven wrong.

This implies that a simple duplication of 19th century technology is going to be difficult to achieve. We lack the easy availability of the materials and the machinery (unless you want to install a paper factory in your garage and start collecting rags.)

I recommend the paper museum link in the "links" section for more information on paper manufacturing and history.

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© Ken Cupery 2011