Brightness of Paper

1383 Words 6 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
…show more content…
This test will help us to better understand how the brightness of paper can be improved through the use of different brightening processes, as well as help us understand what type of papers would be best for different end use applications.
Practical Application
It is important for the operator to understand the brightness of paper concept as a papers brightness directly effects the contrast and sharpness of a printed image. It is important to understand that high brightness papers are not always preferred, as lower brightness papers produce an image that has less contrast and sharpness and therefore produces less strain on the reader’s eyes. Therefore the operator must understand the end use application and select the best possible paper for the application. It is also important to understand how different brighteners affect the paper. Fluorescent dyes are added to paper to increase its brightness; however fluorescence in paper can be cause loss of saturation in pale yellow printed colors (Preucil, 1961). The operator must also consider metamerism issues if the approved proof is printed on paper that has different fluorescent properties than the press sheet (Field,1999)

Definitions
Brightness: A paper property, defined as the percentage reflection of 457nm radiation.
Fluorescence: The emission of light by a substance following the

Related Documents