Mechanical wood pulp
Description
A mass of wood fibers produced by physically grinding rather than chemically treatment. To produce mechanical wood pulp, bark-free, cut wood is sent to a sandstone abrasion-type grinding machine. It is then screened and filtered to remove large pieces and foreign material. The resultant pulp contains Lignin, Hemicellulose, Resin, and colouring materials which yellow and deteriorate the paper over time. Thus, the pulp is often bleached with Peroxide or hydrosulfite to improve whiteness. Groundwood paper is produced from coniferous trees. It is inexpensive and has low strength but high opacity and bulk. It is used for newsprint and other low cost printing papers. Groundwood paper is chemically unstable.
Synonyms and Related Terms
mechanical wood-pulp; groundwood pulp
Physical an Chemical Properties
Tests used to determine the presence of mechanical wood pulp in a paper are: 1) Iodine-Zinc chloride test gives a positive yellow, 2) Aniline sulfate turns yellow for positive, 3) Paranitroaniline turns orange, 4) Phloroglucinol turns red (Roberts and Etherington 1982), 5) and Graff "C" stain will turn yellow due the presence of lignin.
Additional Images
Softwood groundwood pulp stained with Graff "C" Stain at 10x
Softwood groundwood pulp stained with Graff "C" Stain at 40x
Resources and Citations
- R. J. Gettens, G.L. Stout, Painting Materials, A Short Encyclopaedia, Dover Publications, New York, 1966
- Matt Roberts, Don Etherington, Bookbinding and the Conservation of Books: a Dictionary of Descriptive Terminology, U.S. Government Printing Office, Washington DC, 1982
- Encyclopedia Britannica, http://www.britannica.com Comment: "Papermaking." Accessed 15 July 2004.
- Walter Rantanen. "Fiber ID Course." Integrated Paper Services. June 2013. Lecture.