This information is reprinted from the For Beginners column of Hand Papermaking Newsletter #92 (October, 2010).
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The fibers you use and the way you prepare them can produce a vast array of papers; you can stretch this range of properties even further by combining additives with your pulp. You might do this to affect the surface of the paper, the way it accepts ink, its opacity, or its pH. One of the most common additives in Western style papermaking is sizing. A ketone dimer sizing such as those sold by papermaking suppliers is a synthetic liquid mixed into your pulp after beating to prevent ink from bleeding when applied to the dried paper. Alternately, paper can be externally sized with gelatin after it has dried.
Some ketone dimer sizing can double as retention aid (or retention agent). Retention aid may be purchased in powder or liquid form and helps pigment adhere to the fiber. Directions for use vary with supplier. When using the ketone dimer sizing as retention agent, the pulp is thoroughly mixed with this additive before mixing in pigment. When using a separate retention agent, this is often mixed in after the pigment, causing the pigment that had been floating around in the water to suddenly cling to the fiber with seeming magic, clearing the water of pigment and indicating that the pulp is not over-pigmented and thus should not bleed. I have found that pigments are absorbed most readily when using retention agents provided by the same supplier as the pigments. Certain pigments will adhere more readily than others. The particular pigments that give you trouble may vary with the make-up of your water.
Formation aid (synthetically, polyethylene oxide or PEO) can have several effects. Formation aid is a slippery, slightly gelatinous liquid that aids in Japanese-style sheet formation. Formation aid gives a smooth flow to the fibers, and thus is often added to pulp paint to help control its spread. It also slows the drainage of the pulp, so can be utilized in work in the deckle box or in creating very large sheets of paper where the manipulation of the mould in sheet formation is slower. Coagulant (polyacrylamide powder or PNS) can also act as a formation aid if no other additives are present in the pulp and will act as a flocculent, causing fibers to clump. This can be used to decorative effect, adding flocculated fibers of one color to a vat of another color. Natural formation aids include tororo-aoi, a root that traditionally supplied this additive for Japanese-style papermaking, and okra.
Calcium carbonate can be added to pulp as an alkaline to lower the pH, and will make the resulting paper more opaque as it fills the spaces between the fibers. This can be desirable for digital or other printing processes. (See “For Beginners” in Hand Papermaking Newsletter #82 for more on making paper for digital printing.)
Read the manufacturer’s directions to start, and experiment to expand the range of effects you can create with your handmade paper. Keep detailed records in your paper sample book so you can reproduce your most successful proportions. This is especially important once you bring these papers into other creative processes that have their own sets of variables.
Copyright 2010 Hand Papermaking, Inc.