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Comparative Study of Brightness/Whiteness Using Various Analytical Methods on Coated Papers Containing Colorants

Summary: Comparative Study of Brightness/Whiteness Using Various Analytical Methods
on Coated Papers Containing Colorants
Burak Aksoy, Margaret K. Joyce and Paul D. Fleming
Department of Paper and Printing Science and Engineering,
Western Michigan University, Kalamazoo, MI, 49008
Fluorescent Whitening Agents (FWA), dyes and pigmented inks are used extensively in the paper industry
to enhance the appearance and optical performance of coated and uncoated papers. There are several
different systems in use for the description and specification of color and optical properties of paper, using
colorimeters, spectrophotometers and brightness meters. CIE and TAPPI are the most commonly used color
systems in the paper industry. In this study, three different colors (blue, black and red), and FWA were
added into coating formulations from three to five addition levels. Coated LWC papers were measured for
their optical properties with two different spectrophotometers and a brightimeter. The CIE whiteness
formulation (1996) was analyzed on slightly colored papers.
It was found that in some cases, calculated CIE whiteness values increased with increasing amount of
colors in the coating layer, although the papers appeared darker or redder to the observers. Small deviations
in measured CIE tristimulus functions X, Y, and Z often caused significant changes in calculated CIE, and
Ganz whiteness values. Hunter whiteness values also followed the same pattern as CIE and Ganz
whiteness, although it is less sensitive to small changes in the tristimulus values. The results show the
deficiencies in the current measurement techniques for assessment of brightness and whiteness of wood


Source: Abubakr, Said - Department of Paper Engineering, Chemical Engineering, and Imaging, Western Michigan University


Collections: Engineering