Pulp & Processing
In early Western papermaking, paper was made from linen and hemp rags that had been retted, often cooked in an alkali and flushed with water while being pounded to a pulp. This is a fine place to start, but a bit equipment- and labor-intensive. We can skip all that hard work by turning to paper pulp suppliers who sell various fibers that have been partially processed and are ready for blending or beating and sheet forming. Paper suppliers sell many varieties. Some need only be blended; others (like kozo) need to be cooked and pounded.
Besides linen and hemp, one can produce a wide variety of paper from flax roving, abaca half stuff, cotton rag, and cotton linter. Each has its own appeal, characteristics, and processing needs. Whereas linen is more likely to make crisp, rattly writing paper with very little processing, fibers sourced from seed hair (like cotton rag and linter, for example) can produce blotter paper when beaten briefly; further processing is required to make printmaking papers and even more for writing papers.
[...]Hydration and fibrillation occur during fiber processing, when the heavy hammers of a stamper and the beater blades of a beating engine smash into wet shards of linen and hemp rags, causing the fibers of the cloth to stress, fray, and swell with water. Various degrees of hydration and fibrillation are responsible for producing the wide variety of papers we have come to enjoy. While shorter fibers articulate laid lines and are desirable in some watermarked paper, folding endurance and tear strength are eventually diminished by prolonged processing.[...]
Obtained from the phloem or outer bark of jute, kenaf, flax and hemp plants, bast fibers (similar to traditional Japanese paper fibers) are very durable due to hemicellulose, a natural binder not found in abundance in seed hair fibers. Treated properly, these bast fibers can produce a crisp, rattly sheet of paper without a prolonged process of brutally beating and hammering on the bark fibers. Kozo, mitsumata and gampi are the three main fiber species whose inner bark (bast) fibers are used in Japanese papermaking. Hemp, mulberry, bamboo and straw are used to make washi. If you elect to use these amazing plants, the inner bark (with the outer bark already stripped) is also available from papermaking suppliers. Preparing these fibers for papermaking requires soaking, cooking for half a day in a mild alkali (like soda ash), rinsing, and pounding with a mallet. In this papermaking paradigm, longer processing (cooking) produces softer paper while shorter cooking yields harder paper, as more of the natural binder hemicellulose is lost the longer it is left in the cook.
-excerpted from Donald Farnsworth's Determinate Papermaking, 2017