Papermaking
The art, science, and technology of papermaking addresses the methods, equipment, and materials used to make paper and cardboard, these being used widely for printing, writing, and packaging, among many other purposes and useful products. Today almost all paper is manufactured using industrial machinery, while handmade paper survives as a specialized craft and a medium for artistic expression.
In papermaking, a dilute suspension consisting mostly of separate cellulose fibres in water is drained through a sieve-like screen, so that a mat of randomly interwoven fibres is laid down. Water is further removed from this sheet by pressing, sometimes aided by suction or vacuum, or heating. Once dry, a generally flat, uniform and strong sheet of paper is achieved.
Before the invention and current widespread adoption of automated machinery, all paper was made by hand, formed or laid one sheet at a time by specialized laborers. Even today those who make paper by hand use tools and technologies quite similar to those existing hundreds of years ago, as originally developed in China and Asia, or those further modified in Europe. Handmade paper is still appreciated for its distinctive uniqueness and the skilled craft involved in making each sheet, in contrast with the higher degree of uniformity and perfection at lower prices achieved among industrial products.
While monitoring, regulations and action by concerned citizens, as well as improvements within the industry itself are limiting the worst abuses, papermaking continues to be of concern from an environmental perspective, due to its use of harsh chemicals, its need for large amounts of water, and the resulting contamination risks, as well as trees being used as the primary source of wood pulp. Paper made from other fibers, cotton being the most common, tends to be valued higher than wood-based paper.
As a first step, cellulose fibres must be separated, impurities removed, and fibres processed to open up the fibrils, in a process or combination of processes among the following, or others, resulting in paper pulp. Especially for paper being manufactured directly from plant sources, be it bark, wood chips or leaves, the removal of non-cellulose components is the main goal at this time.
Breaking apart of the source material is done by mechanical means, often accompanied by heat and chemicals, in abundant water, followed by rinsing. Before the enforcement of responsible protocols became the norm, or where they are not enforced yet, the disposal of the harsh chemicals employed, large amounts of water polluted during rinsing, and contaminated steam polluting the air result in the loss of environmental quality. While very small in scale compared to large paper mills, hobbyists and cottage makers of paper need consider te environmental impact of their practices, and also prefer those with a minimal impact.
Responsible paper manufacturing practices require the recapture, treatment and reuse of the water and chemicals used, within strict safety and environmental protocols that are enforced according to local laws and custom. Until those the
Pulping is the process involved in extracting and preparing cellulose fibres from wood, rags or grasses.
"Macerating" chiefly depends on natural organic fermentation and time, the first step in the traditional pulping method. Tends to be gentler environmentally, as milder chemicals are used, if any, mostly relying in the decomposing action of natural yeasts. Macerating is similar to retting.
"Cooking" uses chemicals plus heat. Industrial paper mills achieve pressure and higher temperatures in large digesting chambers, hobbyist using a chemical-safe container, as many of the chemicals used would dissolve aluminum kitchen pots. Either must follow strict safety procedures. Some softer fibers need just some boiling in water to separate from their matrix and from each other. The main advantage of cooking is being much faster than macerating.
File:TheCritterBeater.jpg the Critter, a small Hollander beater manufactured in New Zealand"Beating" is mostly a mechanical process, accompanies, follows or is done instead of macerating or cooking.
"Stampers" used to be the primary tool in Europe until the adoption of the Hollander beater, Jordan beater, and hydropulpers. When used at an industrial level these machines are correspondingly large, while smaller versions are used by small-scale papermakers.
Many artists and hobbyists today use a common kitchen blender to prepare small amounts of pulp.
Preparation of gampi and some natural fibres, as well as recycled paper and repulping of industrial pulp need a minimal amount of beating compared to other sources of pulp, often being done with a paddle or a hand-held mechanical mixer.
File:AbacaPulpSheet.jpg a sheet of abaca pulp from the Philippines, as purchased in the United States. Abaca is a tropical plant related to the banana
Frequently paper pulp will be manufactured close to the source of fiber, then paper itself elaborated elsewhere. Water is removed from the pulp to reduce shipping costs and ease transportation, the pulp pressed and dried into thick sheets. This kind of pulp can give advantages to the papermaker, especially for those operating in a small scale: it allows access to types of pulp that would not be available from local sources, is less time consuming to prepare, and avoids the need to manipulate chemicals and then dispose of them, also reducing the corresponding use of water for rinsing.
Pulp is often bleached. Historically the UV action of the sun has been used, then chlorine-based chemicals became prevalent in the more recent past. The use of chlorine by paper mills is criticized as among the worst causes of papermaking pollution, in water, soil and air, especially dangerous in persisting organochlorines such as dioxin and others, worse when elemental chlorine is used. Safer chemicals such as oxygen are preferred in places where strict environmental oversight is enforced, often as hydrogen peroxide, this substance, and the sun, being the less dangerous means to bleach paper pulp available to the small papermaker.
Next, the pulp is mixed in a vat with large amounts of water and some additives to form "stuff", actually beingthe proper technical term for a thin suspension of paper pulp fibres in water as separate from each other as possible.
additives:
one of the most common is calcium carbonate, to promote an alkaline buffer that will prevent paper from breaking down in time. Research would indicate that earlier paper had a substantial, higher proportion of calcium carbonate, often from crushed limestone, but also from egg and oyster shells.
pigments to color the paper
formation aid, to thicken the stuff and promote better separation of the fibres is essential to some Eastern papermaking methods
sizing, to avoid ink from being absorbed by the paper too readily and to strengthen the paper, though often sizing is applied at a later step after drying as a coating, and not in the vat. Historically the most common sizing agent has been gelatin.
Then, a sheet of paper is formed or laid down when water is removed using a sieve or screen-like device.
In handmade paper this tool is called a mould, in industrial papermaking it will be an endless belt of a mesh-like material.
Either the mould is dipped in the vat, or prepared stuff in some container is poured on the mould.
Dipping, shaking, and lifting the mould from the vat sometimes requires considerable skill to achieve a uniform sheet of paper, as well as strength, especially for larger moulds. Some very large pieces of paper need several operators working together to complete this task.
generally gravity is the only force used for the first separation of water, but most industrial and some handmade paper methods depend also on vacuum, suction, and blotting.
The steps to follow those listed above are the object of much variation according to the tradition, machines, or innovations being used, but all share the same objective, that being to remove the most of the water, to result in a dry sheet of flat paper or paperboard.
In handmade paper each sheet formed is removed from the mould and piled on top of another prior to pressing, a procedure called "couching". In Western traditions a piece of felt is then added, separating each sheet. Most Eastern traditions do not use felt, instead adding just a string to facilitate separating the sheets after pressing. Some other traditions, chiefly in Central and South Asia, have depended on the sheet of paper drying directly on the mould, thus requiring multiple moulds for paper production.
It is often said that the press used by papermakers saw its origin in the oil presses available in agricultural regions. A converted car jack hydraulic type of press powers this step among many small papermakers today, and is also found in the laboratories of large paper mills.
Endless belt industrial papermaking machinery is designed in such a way as to complete drying by pressing, vacuuming and heating steps, resulting in a continuous very long single piece of paper. This often also involves calendering, where high pressure rollers achieve a smooth and shiny surface, sometimes also coating the paper with additives. The finished paper is then gathered in a roll, or else cut to size and packaged.
A "drying loft" was an essential feature of Western paper mills before automated machines, where paper was hung to dry on cow-hair ropes, that would not attach to the paper. Similar principles are still in use today among some artisan papermakers, while other favor forced drying using a fan in a box, among many options.
B. Franklin shared Chinese methods to accelerate the drying of paper using a heated surface, in an attempt to have American papermakers adopt those.
While a drying mat of rotten nets fibre by the seashore is part of an often repeated legend of the origins of paper in China, Eastern papermaking has used for thousands of years mulberry, gampi, bamboo, lokhta and other plans as the source of fibre.
Western papermaking has been historically the first major industry to depend on recycling: for hundreds of years the main source of fibre was rags, as in broken-down clothing that instead of being discarded or burned as useless trash was transformed into this new and valuable product, paper. Since the beginning of European and then American paper there was a serious dependency on linen and hemp clothing rags, old cordage, nets, and sacks, with frequent shortages and specialized laborers and businesses. Later, cotton from the American colonial plantations used in clothing became also an important source of rags, but papermaking had to wait for fibre from wood to really take off in the way we know it currently.
Most papermaking today depends on cellulose fibres extracted from wood using harsh chemicals and high temperature to remove lignin and other impurities, and bleach the pulp. Rags for pukp have almost disappeared, but recycling for paper has had a revival, especially cardboard for packaging will often exist in a cycle where the fibre is used over and over again, while post-consumer waste such as books, newspapers, office paper often form a percentage of a mix with pre-consumer waste and virgin fiber in some products that tend to be offered at higher prices than those made out of virgin wood pulp.
Contemporary alternative sources to cellulose from wood include the traditional plants, in some cases, such as with hemp and linen, being used directly as virgin fibre from the plant instead of trying to find the appropriate rags. Rags used for papermaking have become a specialty, because artificial fibers are so prevalent and hard to recognize and then remove once pulped. Cotton linters, which are the short fibres discarded by the textile industry, are especially appreciated for higher priced paper, often mistakenly labeled as being from rags.
The three main classic methods for papermaking by hand that Dard Hunter described in the early 20th century are still in use by modern practitioners. Some variations combine features from several traditions, while the availability of some machines has made certain steps easier than they when only manual labor was available.
The major distinguishing characteristics of these traditions are as follows:
So called "Western papermaking" uses moulds where the screens are attached to the frame. Couching involves a piece of felt placed between each sheet. This method has been used almost in the exact same way since its earliest records in the 15th century until modern times. The only major change was the adoption of wove screens displacing laid screens starting in 17??.
So-called "Eastern papermaking" as traditionally practiced in Japan and Korea and adopted by others elsewhere, requires a thickening formation aid chemical added to the vat. The screen is amovable from the frame, and sheets are piled up on top of each other for pressing. This method only uses "laid screens", that is, those where many parallel elements such as thin bamboo members form the sieve-like device used to concentrate the cellulose fibres to form the sheet of paper.
So-called "Tibetan papermaking" uses moulds where the screen is attached to the frame, the sheet of paper drying directly on the screen, no couching or pressing being done prior to drying. Also, the mould is not dipped in a vat, but instead floated on a pond and the stuff poured unto it, and then spread and distributed within the frame using a stick. The traditional use of wove fabric, such as silk, is seen by Dard Hunter as this being perhaps the original, over 2,000 year old papermaking method.
The oldest fragments of paper with writing, discovered in modern-day China, have been dated as far back as 200 years BCE. All variants of cellulose pulp papermaking that have been developed elsewhere trace their origins to this region of the world[a]. China is today the main industrial manufacturer and exporter of paper and paper products worldwide, although the adoption of machinery wasn't widespread in that country until the second half of the 20th century. While quite significant already, prior to the 1960s papermaking in China was the result of a cottage industry, with small and larger mills depending on manual labor and local sources of fiber, such as bamboo and grasses, with a somewhat large variation in the methods and tools used.
Endless belt machines, much improved after the Robert and Fourdrinier inventions of 1799 and 1801 respectively, today produce very uniform and reliable products at ever expanding industrial scale, as a continuous sheet of paper rolled up, eventually cut to size and packaged as is, or following other manual or industrial processing such as printing and coating.
Since the invention of the Fourdrinier machine in the 19th century, most paper has been made from wood pulp because of cost. But other fibre sources such as cotton and textiles are used for high-quality papers. One common measure of a paper's quality is its non-wood-pulp content, e.g., 25% cotton, 50% rag, etc. Previously, paper was made up of rags and hemp as well as other materials.
Economic, social and cultural impact of papermaking
Investment in papermaking associated with innovations in its manufacture have followed closely the progress of printing and literacy. Likewise, in a certain way as a circle, the availability of paper in a certain locality is necessary for the flourishing of printing, writing, and consequentially, the sharing of ideas there.
Historically, high tariffs for import of paper, and the absence local papermaking or its prohibition are easy to correlate with low literacy, low participation in politics, and lessened development, as well as the contrary effects when those policies and local papermaking ventures exist, this contrast being easy to see between the British colonies in the Americas, and the Spanish and Portuguese ones.
For these reasons the United States in its international aid after WW2 was promoting the making of paper, even in a small scale, reasoning that local teachers and other users of paper would be empowered by its availability and able to be more effective in the development of poor and devastated territories.
As a side effect, the rise in need for wood from trees to manufacture pulp has encouraged large companies to plant fast growing trees. This has even become a national policy in Uruguay, a country known as generally devoid of forest, now covered with extensive plantations of eucalyptus, the growers benefiting from some subsidies. Some of these developments, however, have been criticized as encouraging monocultures and being "not in my backyard" policies, as for example, eucalyptus globulus is considered a pest in parts of the United States, while multinational companies encourage its planting in Uruguay.
The fact is that paper, as a material fit for printing, is continuously falling in price and rising in availability. Because the pulp mills are more efficient when very large, requiring a like-size investment, this results in the ownership of industrial pulp and paper worldwide becoming concentrated among fewer giant multinational companies, while small paper mills and cottage paper makers have but disappeared, except for the ones serving a narrow market of those who can pay premium prices for very specialized products, or artistic and vanity crafts.
While papermaking was considered a lifework, exclusive profession for most of its history, the term "notable papermakers" is often not strictly limited to those who actually make paper. Especially in the hand papermaking field there is currently an overlap of certain celebrated paper art practitioners with their other artistic pursuits, while in academia the term may be applied to those conducting research, education, or conservation of books and paper artifacts. In the industrial field it tends to overlap with science, technology and engineering, and often with the pulp and paper business.
Some well known and recognized papermakers have found fame in other fields, to the point that their papermaking background is almost forgotten. One of the most notable examples might be that of the first humans that achieved flight, the Montgolfier brothers, where many accounts barely mention the paper mill their family owned, although paper used in their balloons did play a relevant role in their success, as probably did their familiarity with this light and strong material.
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