종이작업(파삐에 꼴레)

[폴리오]

Abstract
The prairie paper project was designed with students in fifth through tenth grade in mind. I developed it in my home kitchen with the help of my daughter Rachel, a fifth grader. This project teaches a basic industrial technology, papermaking, and it provides opportunities to introduce some basic chemistry and environmental issues, as well as exploring the artistic possibilities offered by home made paper.
This project is not packaged for classroom use; that is left up to the project leader! Depending on the level of the students and the time available, the project leader may have to do more or less preparatory work; the project can probably be completed in one day, but it is probably preferable to spread it out over four sessions.

Introduction
Papermaking in the 20th century in the United States is strongly associated with pulpwood, but it was not always so. The ancient Egyptians used papyrus, a wetland reed, to make paper. The preferred raw material in the late middle ages was linen rags, that is, used cloth made from flax, nettle or hemp fibers. In 19th century America, there were paper mills that made paper from materials such as oat straw.

The Prairie Paper Project is an introduction to papermaking using straw. To further the connection to the vanishing natural environment of the Midwest, I used straw from big bluestem grass, one of the grasses that once towered over Iowa's tallgrass prairies. Any other source of straw would have worked. One of the most interesting sources of straw for such a project would be reed fragmides grass; this is used as a source of commercial pulp fiber in parts of eastern europe. Reed fragmides grass is a plume-topped wetland grass that grows to heights of 14 feet and is common in roadside ditches in the northeastern United States, with some patches found as far west as central Iowa.

Papermaking begins with the collection of raw materials, and continues through the preparation of the raw material, making pulp, screening out the sheets of paper, drying the paper and optionally, finishing the paper. This presentation begins with a summary of the materials and tools you need for making your own paper, followed by step-by-step instructions for making paper from straw.


Materials, Tools and Supplies
A pair of pruning shears, a sickle, or even a pocket knife will come in handy for harvesting the straw used for papermaking; poultry shears work very well for cutting up the straw, particularly the kind with a notch near the base of one blade.

You need two plastic buckets, one for soaking the straw, and another for preparing the alkali solution used later for boiling the straw. For small projects, plastic one-gallon milk jugs with the top cut off work well.

The caustic solution you need for boiling the pulp can be extracted from fireplace ashes. A bucket full of ashes will suffice; the ashes should contain very little charcoal or unburnt twigs, but small amounts of such impurities will cause no problems. If you prefer to buy your chemicals instead of extracting them yourself, sodium hydroxide (caustic soda, also known as drain cleaner) works as well.

Rubber gloves and safety goggles. All the standard precautions taught in junior high science classes for the handling of strong acids and bases apply to the caustic solution you'll be using to boil your straw.

An anvil, hardwood cutting board, or a heavy stone block. You need some work surface on which you can beat your straw into a pulp. What matters is that the surface is at least a foot square, preferably a bit bigger, and that it will stand up to a beating whith whatever you use for a hammer.

A wooden or rubber mallet for crushing your straw and pounding it into pulp. I used the flat end of a flat ended hardwood rolling pin, but a real mallet would have been better.

A stainless steel pot for boiling the straw. The solution you'll be boiling is caustic enough to attack aluminum! The solution leaves no residue, unless you boil it dry, so no unusual cleaning measures are required after use before using the same pot for food preparation.

A large sieve, preferably plastic or stainless steel mesh, for filtering the caustic solution used to boil the straw. Most common kitchen sieves are tin plated steel; the caustic solution may blacken these, but this is not harmful. Do not use an aluminum collander; the caustic solution will attack it! A paper towel or rag to line the seive improves the final filtering of the solution.

A blender for converting your straw to pulp. By the time your straw is ready for pulping, it is clean enough that it won't interfere with later use of the blender for food preparation after a normal cleaning.

A rectangular tub to hold the dilute pulp. This must be fairly large. I used a large kitty litter tray; this was just barely large enough.

A framed screen to lift sheets of pulp out of the tub. This must fit comfortably in the bottom tub, with ample room on the sides for your hands. Fine mesh window screen is on the coarse side, nylon stocking material is a bit too fine. Both should work if they are tightly stretched over a wooden frame.

A pair of boards larger than the screen, for pressing and preliminary drying of the paper. This is optional! There are other ways to dry the sheets.

A supply of felt or denim rectangles larger than the screen, to separate the sheets of paper during pressing and drying. Again, these are optional.

A smooth clean surface to hold the paper during the final stages of drying. Picture windows, formica counter tops, or similar surfaces are all effective; alternately, an oven or clothes-iron to provide the heat needed to dry the paper quickly.

A putty knife, pocket knife, or butter knife to help lift sheets of dry paper from the surface where you left them to dry.

Cleaning supplies to clean up after the project. You'll be very lucky if you don't spill quite a bit of water, and when you beat the pulp, it'll spatter everything nearby. If you dry your paper by sticking it to a counter or window, there'll be little bits of pulp left behind that need cleaning up.


Raw Materials
I harvested a big fistful of big bluestem straw from a native prairie remnant in Iowa City in the early spring, long after the seeds had fallen from the stems. In years where there is heavy snowfall, most of the stems will have been beaten down by that time of year, so an earlier harvest may be appropriate. It's irresponsible to harvest native grasses from an endangered ecosystem such as the tallgrass prairie before they drop their seeds, but with big bluestem, the seeds fall soon after the first snowstorm. You don't have to worry about adverse effects of trampling a prairie remnant when the ground is frozen, but you should be particularly careful when the ground is wet.

The nodes or joints in a grass stem aren't great for papermaking, so I chopped them off and only used the internodes, the straight stiff segments of stems between nodes. I also stripped off the grass leaves and used only the hard stiff stems themselves. Big bluestem grows to heights of over 6 feet (2 meters), and the internodes are long enough that this wasn't very labor intensive. You can make a few sheets of paper from one fistful of internodes, and a large fistful of grass gave me enough for an ornamental display of big bluestem as well as enough internodes to make a small stack of paper.

I soaked the internodes for a week in cold water, as a preliminary step, to begin softening the pulp. The water turned yellow-brown with pigment leaching out of the stems, so I changed the water a few times during the soaking. This long soaking was probably unnecessary; an overnight soaking would probably have been sufficient.

While the grass was soaking, I filled a bucket half full of water and then added enough fireplace ashes to it that it was 3/4 full of the ash/water mixture. Part of the ashes dissolves in the water, making the caustic solution you'll need later. After the ashes had soaked for a while, I poured the mixture through a seive into a stainless steel pot, discarding the seived out wet ashes in a plastic bag in the garbage. Some ash managed to get through the seive, so I transferred the solution back to the bucket, rinsed the pot, and then lined the seive with a sheet of paper towel before filtering the solution again. The solution that results is highly caustic (it is a strong base). Safety note: Keep your hands out of this solution, and if it does splash on you, rinse it off immediately with lots of water. A sign of danger when working with caustic solutions is a soapy sensation between your fingertips; this is the result of a chemical reaction between your skin and the caustic solution that makes soap as it eats away your skin. Time for rubber gloves and goggles!

Historical Note: The first patent granted by the US Government was on July 31, 1790 to one Samuel Hopkins of Vermont for a process of making potash (potassium carbonate or potassium hydroxide), from wood ashes and pearl ashes. This patent was signed by George Washington as President and Thomas Jefferson as Secretary of State. There were only 3 other patents issued that year by the US Government. (Thanks to H. H. Murray)


Preparation for Making Pulp
It is possible to make pulp directly from soaked grass stems, relying entirely on mechanical methods (beating and chopping) to separate the cellulose fibers from the stems. Such pulp is called mechanical pulp and is generally considered inferior because the extra beating required shortens the fibers and because the plant residues in the paper speed its eventual decay. Mechanical pulp is perfectly appropriate for newsprint -- the process is cheap and we don't care of yesterday's newspaper turns yellow and brittle tomorrow.

To make a higher quality paper from your soaked grass stems, you'll have to chemically soften the bond between the cellulose fibers in the stems. In the papermaking industrym, pulps made this way are classified as chemical pulp. I did this by boiling my grass stems in the caustic solution described above, so what I made is an alkali or basic pulp. There are also acid pulp processes and some that use neutral chemistry. It is noteworthy that the kraft process used to make the pulp for kraft paper, the brown paper used for paper bags and corrugated cardboard, is also an alkali process, and is only slightly more complex than the process described here.

Before I started my chemical pulp processing, I crushed the wet grass stems in order to speed the penetration of the solution into them. If I'd had access to a rolling mill such as is used for sugarcane or sorghum, that would have been helpful; a rubber mallet would also have worked. I used a kitchen rolling pin, and as a result, I could only crush a small handful of stems at a time.

After crushing, I boiled the stems in a stainless steel pot for perhaps 30 minutes. The smell quickly shifted from the lingering smell of fireplace ashes that originally hung over the caustic solution to a sugary smell. The smell of sugar is no accident! The hard parts of a grass stem are made of cellulose fibers cemented together by lignin and hemicellulose, just like wood. When you boil this mixture in your caustic solution, it attacks this cement, breaking it down by a chemical process known as base hydrolisis while leaving the longer cellulose molecules largely unchanged. The products of this chemical breakdown are sugars from broken cellulose mollecules and an assortment of vanillin-like compounds from the lignin that enhance the sweet smell.

After simmering, the liquid in the pot was dark brown and very sweet smelling. In the chemical industry, this liquid is known as black liquor; I poured it down the drain. This liquid waste is no more dangerous to the sewer system than food wastes you might dispose of while cleaning your kitchen, and any residual caustics in the solution are no more dangerous to the sewer system than drain cleaners. Municipal sewage treatment systems can handle small quantities of these chemicals with no difficulty.

I rinsed my boiled grass stems twice, and then wrung them out, freeing more brown liquid before I rinsed them again. Wringing out the stems, you'll discover that they're soft and pliable, quite different from the stiff stems that went into the pot an hour previously. Furthermore, when you wring out a handful of stems, the fibers begin to separate. That's a sign that you've gotten rid of most of the lignin and that the cellulose fibers are free and ready to be pulped! Safety note: Thorough rinsing and wringing removes the last of the caustic solution. After this point, you can safely handle the stems and pulp with your bare hands.

If you want to take a break and come back on another day to complete your papermaking, this is a good time to stop. Store your cooked and rinsed straw in clean cold water until you can get back to it.


Making Pulp
There's a labor intensive way to make pulp, and an easy way. Try both! The labor intensive way is to beat your boiled straw into a pulp, literally. This is messy, but it produces a high quality pulp. Take a small fistful of softened grass stems and put them on your beating block, then begin beating them. I used a rolling pin. Work until you've got a blob of stringy wet mush with little evidence that it was ever straw, then set that aside and start beating another fistful. It's hard to overbeat your pulp using muscle power.

In the middle ages, one of the first applications of water power to industry was in the automation of pulp beating. In a hammer mill a row of hammers is mounted over a trough holding the pulp to be beaten, and the water wheel powers the cam system that automatically raises and drops the hammers.

Today, the lazy man's way to make pulp is to use a blender. Cut a small handful of softened grass into chunks no longer than an inch (any longer, and the fibers will be long enough to snarl up your blender), add half a blender full of water, and then blend at high speed until it's a creamy pulp; about a minute seems to do. Pour out your finished pulp into a waiting tub, and then check the blender's blades before you process another handful of fibers; the blades frequently accumulate a snarl of long fibers.

Pounded chemical pulp has some very long fibers, while blender pulp fibers are all short -- you cut them short to start with, and the blender blades sliced the fibers even shorter as they finished the pulping process.


Lifting out Sheets of Paper
The actual papermaking process requires a tub and a mold or screen. I used a large kitty-litter tray as a tub to hold the pulp, and that was barely deep enough. The mold used to form a sheet of paper is a screen mounted on a wooden frame that should be a bit over half the size of the tub you use. The term deckle is sometimes used for the mold or screen used to form sheets of paper, but this term actually refers to a detatchable edge around the top of the mold; such an edge is not strictly needed, and I did not use one for this project.

The screen used for the mold should be open enough to easily pass water while being fine enough to sweep a mat of pulp out of the water. Particularly with the long fibers you get with hand beaten pulp, you can get away with a fairly coarse screen, even window screen, but I used a fine nylon mesh.

If you embroider a pattern on the screen you use for your papermaking mold, the embroidery will show up as a watermark in the paper you make. This is how most watermarks are made! Don't worry about fancy stitching; what matters is that you block some of the holes in the screen. In commercial papermaking, the patterns for watermarks are usually made of coarse wire that is held in place on the wire screen of the mold with finer wire stitches.

Fill the tub 3/4 full with water, then add a fistful or two of beaten pulp or a few blenders full of blender pulp and swish it around with your hands until the pulp is uniformly suspended in the water. For a large tub, you'll have to add more pulp. To form a sheet of paper, dip the mold in the water, edge first, until the edge is on the bottom at one side of the tub, then slide the edge along the bottom slowly as you slip the rest of the mold into the pulp solution, screen side up.

Once you've settled your mold to the bottom, using a side to side motion to avoid trapping pulp between the screen and the bottom, agitate the dilute pulp with a free hand and then pull firmly up on the mold, lifting it out of the pulp. The goal is to pull firmly enough to force water through the screen, while at the same time, avoiding having strong currents flowing sideways over the surface that might wash the accumulated pulp off the screen. The purpose of a deckle or removable frame around the top side of the screen is to block these currents; if you use a large mold, you'd probably profit by adding a deckle to your papermaking mold.

It may take a few trials before you manage to lift a good uniform sheet of pulp out of the tub. If you aren't satisfied with a sheet, it is easy to return it to the tub, just set the pulp-covered surface of the screen flat on the surface of the water in the tub and gentle wiggle it, and the pulp will resuspend itself.

After lifting a sheet of wet pulp out of your tub, it's a good idea to pause to let the water drain away. Tilt the screen slightly out of the horizontal, and as soon as you're confident the wet pulp won't start to slide, tilt it up more steeply, until it's almost vertical, encouraging the excess water to drip from the lower edge.

There are a number of options for removing the paper from the screen. One is to let it dry on the screen and then peel it off after it dries. Another option is to press the paper side of the screen against a dry absorbant surface such as a layer or two of old denim or felt; this is called couching the paper. The dry denim or felt on which the paper is couched sucks the water out of the paper and holds it by capillary action, allowing you to pull the screen away and use it again.

Yet another option is to couch the paper on a hard surface such as a wall, counter top or windowpane and let it dry there. Again, surface tension should hold the new paper to the hard surface as you lift the screen away. This method is the traditional one used in Tibet!

If you couch one sheet of paper directly onto another, you can make two-ply or three-ply paper. Multi-ply paper made with thin plies of long-fiber pulp is sometimes a bit stronger than single-ply paper, and some artistic papermakers will embed things like flower petals between the plies. If you stack up enough plies, you'll make cardboard. One weakness of multi-ply papers is that they sometimes delaminate unless an adhesive is included in the wet pulp -- various gums, gelatin, or starch can all serve this purpose.

When couching a freshly lifted sheet of pulp, always pull the mold away from the wet paper starting at one edge; this makes it easier for a bubble of air to get between the wet screen and the wet layer of pulp. If you have trouble making the screen release the wet pulp, you should have paused longer to let the excess water drain away, but you can sometimes rescue a good sheet of paper by blowing hard from the back side of the screen in order to start an air bubble between the screen and the paper.

If you have a stock of denim or felt squares, pile new squares of dry denim on top of the newly couched paper, and then dip out another sheet and set it down on top of the stack. You can keep stacking alternate layers of paper and denim for quite a while, as long as you keep refreshing the pulp in your tub every time you run low enough that it's hard to dip out a decent layer of paper.

When you're done making paper, you'll have some pulp left in your tub. Do not pour this down the drain. The cellulose fibers in the pulp are almost perfectly designed for clogging drains! Instead, dump your used pulp outdoors where it can decay naturally, for example, on a compost heap. Your pulp is eminently biodegradable and will rot as quickly as the grass from which you made it.


Drying and Finishing
If you stack your paper between dry sheets of denim or felt, as suggested, you can pile the stack on a board, then put a second board over the pile and press out quite a bit of water. Put the bottom board on a slight slant near a floor drain, then pile weights on the top board to press it overnight.

If you want your paper quickly and can't wait overnight for dry sheets of paper, you'll need to speed up the drying process! You can speed the drying process by using multiple layers of dry felt or cloth between each layer when you are couching your sheets, or you can add layers of dry newspaper between layers of denim to soak up the water. If you press, then change the newspaper or intermediate fabric layers and press again, you can remove large amounts of water fairly quickly.

After pressing out as much water as you can by such techniques, you'll need to use some heat to get the last bit of water out of your sheets of new paper. One option is to cook the sheets dry by baking them in a warm oven. The resulting sheets of paper are likely to cockle (develop a rippled texture).

Another option for fast drying to couch the sheets of paper between lightweight layers of fabric, for example, pieces of bedsheet, with layers of dry newspaper or felt added between the lightweight layers. After pressing as much water as possible out of the new paper, the paper-fabric sandwiches can be ironed with a dry iron on an ironing board to drive out the last of the water.

If you aren't in a hurry, you can leave your stack of paper and felt in the press overnight, and come back to it the next day. When you get back to it, carefully peel the still-damp denim off the topmost sheet of paper in your stack, then lift the denim carrying that sheet and plaster the sheet to a hard clean surface before you peel the denim off the back of the damp sheet. If you let your paper finish drying with one side plastered to a flat surface such as glass or formica, it will end up with one very flat side, making a far better surface for writing than you get by oven drying or ironing between layers of fabric.

When the paper is completely dry, peel it off the flat surface. If the surface was very clean to begin with, the paper may actually lift free as it dries. Otherwise, it may stick, in which case you'll have to carefully ease it up from the surface with a knife.

The paper I made this way from big bluestem grass had a light golden color, with a bit of a sheen to the smooth side of the sheets. I've also made paper this way by recycling office paper; the result was almost like blotter paper, but the paper I made from big bluestem grass took ink very well, without any blotting. I have also made some workable quill pens from the stems of big bluestem grass, so an obvious way to use your finished paper is to draw or write on it with a homemade pen. Reed fragmides grass is far better for pen making than big bluestem, and members of the fragmides family, have been used for this purpose for at least two millenia. One fun option is to round out the project by making not only paper and pens, but also ink. Ink made from soot ground up with a bit of water and a bit of liquid soap and then diluted to a thick liquid works surprisingly well.

Some papermakers hammer finish their paper; pounding on the dry sheet with a hammer packs the fibers more closely and interlocks them in much the same way as pounding on a layer of fur makes it into felt. Another final finishing technique worth experimenting with is to starch and iron the paper in exactly the same way you'd starch and iron a shirt. This is called sizing; it makes the paper less absorbent and less transparent, making it better for pen and ink drawing or for two-sided printing. Commercially made paper is frequently sized with starch, clay or gelatin.


Environmental Notes
An interesting way to eval‎uate this project from an environmental viewpoint is to look at the amount of waste you produced and compare that to the amount of paper you produced. How much water did you use? What did you pour down the drain? How much solid waste did you produce? How many paper towels did it take to clean up, and how does this compare with the number of sheets of paper you made? Finally, how could you reduce the amount of waste you produced?

An economic analysis of the project is also worthwhile! How many hours of labor did you put in, and how many sheets of paper did you make? Divide, and you get man-hours of labor per sheet of paper, then multiply by the number of sheets in a ream of commercially available paper to find out how many hours of hand labor went into making a ream of paper before papermaking was industrialized.

The relatively small quantities of liquid waste produced by a project like this are easily dealt with by a municipal sewer system, but when a papermill processes many tons of pulp a day, the chemical residue from boiling the pulp poses huge problems. When large quantities of this black liquor were dumped directly into rivers, the results were locally disasterous.

The situation was improved when paper mills were required to install wastewater treatment systems, at huge expense, but in the long term, the greatest benefit has come from discovering that the wastewater from pulp processing can be used. The key to finding uses for this wastewater is to look at what it contains. The dominant breakdown product of the chemical destruction of lignin and hemicellulose is a somewhat dirty mixture of sugars and phenol compounds. Microbal decay of this solution, when it was dumped into rivers, produced alcohols, ketones, and other smelly environmental poisons. The same decay process, when carried out in a fermenting vat, can produce alcohols, ketones, and other valuable industrial chemicals. Furthermore, the vanillin-like compounds among the lignin breakdown products are a significant source of artificial vanilla flavoring.

Another use for the waste from pulp processing is as fuel. The alcohols, ketones and other chemicals mentioned above are almost all good fuels, but it isn't necessary to reduce the sugars in the waste to alchohol in order to burn them -- as long as the water content of the waste isn't too high, it can be burned directly or mixed with other fuels and burned. It takes quite a bit of energy to boil tons of pulp and then dry tons of wet paper in a commercial paper mill, and burning the waste products from papermaking is one way to reduce a mill's energy costs.

Whether or not the black liquor is fermented, the final result is almost always burned these days in order to recover the ash. This ash, with lime added to restore the alkalinity, is recycled as the basis of the alkali solution used to process the next batch of pulp.

The paper you produce using the method outlined above is not the clean white color of common typing paper, but rather, a pleasing golden color. Paper mills that produce white paper frequently deal with such colors by bleaching the pulp, generally with chlorine compounds, and the wastwater from this bleaching process contains potentially dangerous chlorinated organic compounds. There is an active effort to find alternative bleaching processes, but consumers should be aware that high quality unbleached papers are available when a perfect white color isn't needed.