Revelations Beneath the Surface: Paper and Fiber Microscopy
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is one aspect of paper conservation and often helps in dating the manufacture of the paper, determining the provenance of the paper, and in selection of appropriate treatment procedures to use in the preservation of the paper. This article introduces the principles of fiber identification and presents two case studies of art papers.
Fiber Sources The most common fiber materials used in paper manufacture are from plants. The most important fibers used by the papermaking industry in North America and Europe are the tree species of the coniferous gymnosperms and the dicotyledonous angiosperm, commonly referred to as softwoods and hardwoods, respectively. Other plant fibers used in papermaking are often referred to as "nonwoody" and are frequently used in the manufacture of high-quality fine art papers or in those countries where woodpulp supply is limited. The nonwoody fibers include the bast fibers from the stem of the flax plant, the seed hairs from the cotton boll, vascular bundles from the stem of plants like wheat and bamboo, and vascular bundles from monocotyledon leaves—typically abaca or manila hemp—and sisal. Other types of nonplant fibers such as animal hairs, mineral fibers, and synthetics can be found in specialty paper products (Table I).
Fiber-Identification Procedure Fiber identification involves taking samples from the paper and viewing them at 100 X magnification or greater, typically with a light microscope. The sample is dispersed on a microscope slide using tungsten needles and a water
droplet to isolate the individual fibers. The sample is examined to assess the overall composition of the paper and the morphology (shape, dimension, texture) of the fibers. Samples are often treated with chemically reactive stains or reagents, and the resulting color or reaction observed helps with identification. Graff C stain and other iodine stains1'2 are the most common, all-purpose stains used by paper-fiber microscopists. These stains not only accentuate fiber detail, they stain fibers a range of colors from yellow to blue to red depending on the amount of lignin present in the fiber. This color reaction gives information about the type and extent of chemical processing (cooking, bleaching) used in making the paper pulp. Scanning electron microscopy (SEM) is particularly useful in visualizing the surface qualities of the fiber or paper and in the evaluation of the degree of fiber refinement or beating.
Purpose of Fiber Identification Identification of the fiber content of the paper may aid in dating the manufacture of the paper, determining its origin, understanding the artist's technique, and understanding and appreciating the physical and chemical behavior of the paper. These factors guide the paper conservator in the selection of treatment procedures to use in the preservation of the paper. It is possible to date or at least postdate the manufacture of paper because it is known when certain fibers, fiber mix-
Table I: Classification of Fibers. I.
Plant Fibers A. Wood Fibers 1. Gymnosperms (softwoods:
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