This information is reprinted from the For Beginners column of Hand Papermaking Newsletter #41 (January, 1998).
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Dyes & Pigments
While some papermakers would not imagine tampering with the unaffected shades of natural fibers, others can not imagine making paper without the bounty of color--bright and bold, or soft and subtle. If you incline toward the latter, knowledge of dyes and pigments--including some basic chemistry--is a necessity.
Use of dyes as a colorant has the advantage of penetrating the fiber, resulting in a somewhat more flexible and translucent sheet than paper colored with pigment. Because dyes to not interfere with hydrogen bonding, the resulting sheet is also stronger. However, dyed paper will generally fade over time as the chemical elements continue to react to sunlight and oxygen. And since dyes are water-soluble, bleeding is often a problem; and so is clean-up, as felts, blotters, and even vats absorb the dye. Dyes require a mordant to set the color.
Natural dyes can be made by macerating plant materials, soaking overnight, boiling, straining, then adding fiber to the colored liquid. Dyes are also available commercially.
Pigments are the colorant of choice for most papermakers. Inorganic pigments which come from the earth (e.g., iron oxide, titanium oxide, etc.) have already endured the ravages of time, so the resulting paper has excellent light-fastness. Synthetic pigments have similar properties. Since pigments are insoluble, they must be "attached" to the fiber using a retention agent, which changes the chemical charge of the fiber allowing it to attract the pigment rather than repel it.
Professional pigments available from papermaking suppliers come with suggested formulas for the amount of pigment and retention agent to use based on the quantity of dry pulp. When properly pigmented, the pulp should be colored, and the water should remain clear. A little pulp placed on a blotter should not bleed color into the blotter.
It is important to note that fiber can become saturated with pigment, in which case adding additional pigment or retention aid will only result in extra particles floating around with no place to attach. See Bobbie Lippman's "parking space" explanation in the Summer 1993 issue of Hand Papermaking magazine.
Keep in mind that in addition to the dye or pigment used, there are many other variables: the type of fiber used and how it was beaten, water quality, other additives, time, temperature, etc. As in other aspects of hand papermaking, experimentation and detailed recording of results in your own studio, while tedious, is crucial. The pay off is long-lasting, vibrant, and beautifully colored paper.
Copyright 1998 Hand Papermaking, Inc.