The Specular Reflectance of Paper, 2007 TAPPI Papermakers and PIMA International Leadership Conference

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A gloss meter only measureasing a single number index of specular reflection, but the physical meaning of such a gloss index is not clear. Moreover, a gloss index measured with a typical glossmeter does not provide sufficient information to correlate with the complexities of gloss appearance. Gonio-photometry involves measurement overall angular geometries an disable to characterize specular reflectance completely. However, gonio-photometers are expensive and time consuming to operate. For this reason, the authors developed a relatively simple and inexpensive instrument called amicro-goniophotometer that measures the angular distribution of gloss light. The result is a bidirectional reflectance distribution function (BRDF). In addition, the instrument can scan the entire BRDF over spatial dimensions of a paper resolved to a small number of microns. The instrument has been used to characterize a large number of paper types commonly used in laser printing. The results indicate that this analytical technique has the potential of providing significantly more useful information about the gloss of papers and optical surface characteristics of papers than traditional techniques of gloss analysis.