Brightness of Paper

1368 Words3 Pages

Theory and Concept of Test

Brightness of paper is important to determine and understand because the brightness of paper will directly affect the print quality and color of a job. Brightness is different from “whiteness” of paper in that a “bright” paper can be blue, red, green, or any other color since the test measures the amount of diffused light reflected from the surface, as opposed to the amount of the visible spectrum reflected. Brightness of paper, as defined in Tappi T452, is determined by the percentage reflectance of blue light measured at 457nm by comparing the sample to an ideal white standard (Goyal,2000). There are 2 methods used to test the brightness of paper. Tappi T452 describes a method in which the sample is illuminated at a 45o angle and measured through a blue (457nm) filter. However this method is prone to inconsistency as the instrument is sensitive to the surface of the paper, and therefore requires consistent grain direction orientation for every sample. The ISO brightness tester uses diffused light to illuminate a large area of the sample which results in a measurement that is almost completely independent of the surface of the paper (Wilson,1998). Paper brightness is enhanced using optical brighteners and fluorescent dyes because they emit blue visible light when exposed to ultraviolet light in its surrounding illumination (Wilson,1998). However, optical brighteners are less effective on papers with high lignin content, therefore fluorescent dyes are preferred. Bleached paper fibers will result in a paper with lower opacity which requires the addition of fillers and pigments (Wilson,1998).

Expected Outcome and Educational Gains

Paper with high lignin content (such as newsprint) is expected to have a ...

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...ttention will likely require a higher brightness paper, however jobs such as newspapers and some books do not require high brightness paper as minimum eye strain is achieved with low brightness papers. Some books may require high brightness paper, while others prefer a softer shade. Paper for optical character recognition documents require minimum brightness levels to be permissible.

Works Cited

Wilson A. Lawrence. (1998). What the Printer should know about paper. GATFPress. Pittsburgh.

Field G. Gary. (1999). Color and Its Reproduction. GATFPress. Pittsburgh.

Goyal Hari. (2000). Properties of Paper. In Pulp & Paper Resources on the Web. Retrieved January 24, 2010, from http://www.paperonweb.com/paperpro.htm.

M-Real. (2006). Euroart Plus. In M-Real. Retrieved January 24, 2010, from http://www.m-real.com/arealadvantage/english/productrange/productrange.html.

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