Many types of paper, particularly bonds, ledgers, index, and book papers are bought on the basis of fiber composition. This test method is used to evaluate the fibers in the paper and to ensure the purchaser that the composition and types of fibers are in accordance with the specifications. It will also show whether the composition is free of inferior fibers which the specifications particularly prohibit. It is also significant as to the structure and quality of the paper. In order that the examination may be interpreted into practical significance, it is important that the analyst should be experienced in the field of pulp and paper microscopy.

For accurate results, considerable training and experience are necessary. The analyst should make frequent use of standard samples of known composition or of authentic fiber samples and should become thoroughly familiar with the appearance of the different fibers and their behavior when treated with the various stains.

Morphological characteristics identify special fibers such as straw, flax, esparto, and certain types of wood, such as southern pine, Douglas fir, western hemlock, and various species of hardwoods, so that the correct weight factors may be applied. A knowledge of morphological characteristics of the different fibers is helpful and, in some cases, essential for their identification. Some information on this subject is given in the Appendixes.