Neri (Part 2)

In part 1 of this post, I described neri and spoke of its essential role in sheet-forming. Now, in part 2, I’d like to start by taking a look at some of the common mistakes that are made when referring to neri.

1) Neri is sometimes described as sticky, or a kind of glue or paste, or something that makes the fibres stick together.
The material has similar properties to eggwhites, or to (the substance which exudes from) okra, so I suppose it is sticky in a way. But I don’t advocate the use of the word sticky because it connotes a kind of adhesive, which is not the intended role of neri. Gooey, mucilaginous, viscous, or ropy all seem like more appropriate ways to describe neri. Gooey is pretty spot-on, but unfortunately not particularly grown-up. I think there are two main reasons that neri is misinterpreted as a kind of glue. First, what is now almost universally referered to as neri was historically in certain locations called nori. The fact that nori can also mean “glue” in Japanese, has surely not helped to clarify the role of neri in the papermaking process. And second, while neri is not an adhesive as we normally think of them, it does in fact help the fibres bond to one another on a molecular level. This has to do with hydrogen bonding, the magic behind all papermaking. Neri made from tororo is hydrophilic (having a strong affinity for water), with a negative electro-chemical charge, which is also true of the fibre, leading to strong molecular bonds between the fibre, water, and neri in the vat. As water and neri are forced out of the sheet during the pressing and drying processes, the hydrophillic fibres will seek to replace those bonds they had with water with bonds to other fibres. It is thousands (millions?) of these molecular bonds between fibres that hold the finished sheet together. Remember that neri is essentially absent in the finished sheet. This is key in understanding neri as a formation aid, and not an adhesive. It encourages the hydrogen bonding process during sheet-forming, and in the end “disappears.”

2) Neri is occasionally introduced as a size agent or gum, with the purpose of preventing ink or pigment from bleeding when applied to the finished sheets.
As above, the presence of neri in the sheet-forming process generally leads to sheets with tighter chemical bonds and therefore a less porous surface, but it is not added to the vat with the intention of sizing the paper. To size a paper, the papermaker will not rely on neri, but instead will add a sizing agent, either during or after the sheet-forming process.

CULTIVATION, PROCESSING, AND VARIATIONS
In Japan neri is most commonly derived from the roots of the tororo-aoi plant. In English, the plant seems to be known by many different names, including Sunset Mallow, Sunset Hibiscus, etc. Its scientific name is Abelmoschus manihot, in the Malvaceae (or Mallows) family. Other members of the Malvaceae family include cotton and okra. Indeed, the seed-pods of tororo-aoi can be difficult to distinguish from okra, and okra is sometimes used by hobbyists as a substitute for tororo-aoi. Some papermakers grow their own tororo-aoi, but most order it from a supplier, who grows the roots specifically for the papermaking trade. She prunes back the leaves, stems, and buds of the plant during the growing season to encourage the roots to grow as big as possible. In the fall, she harvests the roots, and ties them into huge bales, and ships them to papermakers across the country. In appearance, the roots somewhat resemble ginger roots.

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At the papermaking studio, the roots are crushed and left to soak in water. The crushing is most often done by hand, with a mallet, but is occasionally completed in some kind of motor-driven stamping device. While soaking over the course of anywhere from a few hours to a few days, the roots will exude a gooey substance. The resultant liquid is strained through a plastic or metal sieve (or historically through cedar  branches!) to remove the roots. Finally, the mucilage is filtered once again through a fine fabric before being added to the papermaking vat.

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Most papermakers in Japan use a solution of a preservative called Creosol to store the roots, and may also use a small amount to preserve any neri that they produce. On rare occasions, the roots are preserved simply by drying them out, but the efficacy of the resultant neri is rather weak. The only papermaker I have met who still preserves his tororo in this way makes gampi paper. He says that since the gampi fibre is shorter in length, and naturally has a bit of its own gooeyness, the reduced efficacy of dried tororo is enough for his purposes.

The most commonly used plant for neri (by far) is tororo-aoi, but some papermakers use nori-utsugi (hydrangea paniculata Sieb) or a combination of the two. Despite its higher price, some papermakers swear by a combination of tororo and nori-utsugi, saying they could not make their characteristic paper if forced to use tororo or nori-utsugi alone. Historically, neri was made from other plants such as ginbaiso (deinanthe bifida), binan-kazura (kazura japonica), and aogiri (firmiana platinafolia), but I have personally only come across one living papermaker who is trying to make and use neri made from these other plants.

As one might expect, synthetic neri is also available. It is a polyacrylamide powder, and when mixed with water, it produces a liquid like that derived from tororo-aoi. Synthetic neri has its advantages, as it is not susceptible to heat, friction, or bacteria in the way that natural neri is. Additionally, the papermaker can store the powder indefinitely under the right conditions, and there are no roots to process or store. However, it does have a variety of disadvantages as well, the most serious of which is that it does not seem to break down and disappear the way that natural neri does. The long-term effects of synthetic neri remaining in sheets, though mostly presumed to be benign, is still not fully understood. Sheets made in the traditional manner (including the use of naturally derived neri) have been shown to last hundreds, even a thousand years or more with little or no degradation. As a selling point, this is an advantage that most papermakers are not willing to cede. Synthetic neri is standard in the machine-made papermaking world, but is still widely frowned upon among hand-papermakers. In the end, however, even the most diligent papermaker may add a small amount of synthetic neri to the vat during the most dogged days of summer.

USAGE
Once the papermaker has prepared his neri (from whatever source), it is ready to be used to set up the vat for papermaking. Once he has mixed the fibre thoroughly with the water in the vat, neri is added. The mixing-in of neri is usually done with a bamboo pole, using long, circular, and sharp strokes. The papermaker will be careful not to mix the solution too long, as neri’s efficacy breaks down with extended manipulation. The papermaker uses his careful understanding of the desired thickness and quality of the paper being made, the base stiffness of the neri, the ambient temperature, the type and quality of the prepared fibre, and possibly other factors, to judge the amount of neri to add, and the length and intensity of mixing. Some papermakers know if they’ve added enough neri based on the sound the bamboo pole makes running through the solution. Others will pick up a handful of solution and tip it back into the vat, observing the condition of the solution as it falls. Some papermakers (especially novices), may need to try forming a sheet to determine if the ratio is just right.

CONCLUSION
I sometimes refer to neri as “the magic ingredient” in the Japanese papermaking process. It really is what allows washi to be washi-like; it gives washi many of its unique characteristics that set it apart from western papers. I hope this description is helpful. Please let me know if you have any ideas or questions about neri by leaving a comment.

Neri (Part 1)

I’m beginning a series of posts that will introduce and describe elements of the world of Japanese paper (washi) and papermaking. I’m picking neri to describe first, because I feel that it continues to be one of the most misunderstood materials associated with Japanese papermaking. In part 1, I’d like to describe the material and explain why it is essential to the Japanese papermaking process. Part 2 will talk about what neri is NOT, and explain how it’s prepared and used.

Along with the prepared bast fibres (kozo, mitsumata, and gampi), and cold, clean water, the third essential ingredient in the Japanese papermaking process is neri. Neri is a mucilaginous liquid derived from plants (usually tororo-aoi – see part 2 for description) that is added to the papermaking vat. The addition of neri slows the drainage of the pulp solution through the screen of the papermaking tool (among other things) and allows the papermaker to more easily form sheets of even thickness.

Sometimes referred to in English as formation aid, papermakers in Japan have made use of neri since some time during the Heian period (794–1195). Washi scholars have ascertained the date for the adoption of neri by looking at the formation quality of historical paper samples — some time during the Heian period, the papers become more even in thickness, with a much cleaner formation quality. Many experts speculate that the adoption of neri came after papermakers found that making paper with gampi fibre, which has its own gooeyness, allowed them more time to manipulate the pulp solution back and forth across the surface of the papermaking screen, resulting in stronger, more even sheets of paper. It’s speculated that this discovery encouraged papermakers to seek out another source for mucilage to add to the papermaking vat for use with kozo and other fibres which have no mucilaginous qualities of their own. Whether neri is a Japanese discovery, or an innovation that entered Japan through (most likely) China or Korea, is still in debate. Historically, papermakers in different regions of Japan referred to the material by different names, including nebeshi, tamo, sana, nire, and most prominently nori (more about nori in part 2). The term neri comes from the papermaking area of Echizen and it seems that use of this word has now spread throughout Japan to the point of being nearly universal, due in part to Echizen’s prominence as a papermaking region.

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Neri has a complex role in the sheet-forming process, but stated simply, neri has three unique characteristics that make it essential to the papermaking process. First, it works to slow the drainage of the pulp solution from the sugeta (papermaking tool), allowing the craftsperson time to manipulate the solution back and forth across the surface of the su (screen). Second, it encapsulates the individual pulp fibres to distribute the fibre evenly in the vat. Third, it more or less disappears when the papermaking process is complete.

DRAINAGE — The most critical function of neri is to slow the drainage of the pulp solution through the su. If a pulp solution without neri is scooped into the sugeta, the water will immediately drain through the su, leaving a clumpy mess on the surface. When neri has been added, the drainage of the pulp solution slows dramatically. In this way, the papermaker has time to deftly rock the sugeta back and forth and from side to side, evenly distributing the fibres across the surface of the su. Stated simply, by controlling the amount of neri in the vat, and thus the drainage rate on the screen, the papermaker can more easily dictate the thickness and quality of the paper.

DISPERSION — The second function of neri is to encapsulate each individual fibre, allowing the papermaker to uniformly distribute the fibre in the vat of water, and retarding the fibres’ natural tendency to sink in the vat. Scientifically speaking, the neri has a negative charge, and after encapsulating the fibre, it works to repel the fibres from each other, which prevents flocculation (clumping) of fibre. Even dispersion leads to sheets of even thickness, but it also allows for stronger and greater chemical bonds, which makes for stronger paper. Japanese papermakers talk about “koshi ga aru” (a kind of firmness) as a highly sought after characteristic, which comes at least in part from stronger and greater bonds. Other desirable traits are a compacted and less porous sheet surface, and a surface lustre — both of which are a result of increased and stronger bonds between fibres, achieved through even dispersion.

DISAPPEARANCE — The third special characteristic of neri is that, even though it has the power to slow the drainage, once the paper is formed, pressed, and dried, neri doesn’t remain in the paper, except in trace amounts. In this way, the resulting sheet of paper is essentially a mat of bonded cellulose fibres. This may seem hard to believe, but chemical analysis of finished sheets has proven it to be true. Somehow the compound breaks down, and is carried away with the water/moisture that is removed during the pressing and drying of sheets. It may be easier to understand when one considers the fact that neri made from tororo-aoi is extremely sensitive to temperature, friction, and bacteria. This is part of the reason why the best paper can be made in the winter season, when neri is most effective, and paper made in the summer, when neri is weak and quick to lose it effectiveness, is usually poor quality, limp paper. The fact that neri weakens and eventually disappears is part of what makes sheet-forming so difficult, but it is also the reason neri can safely be used in the process.