Paper manufacturers need to adjust dyes, pigments and other process parameters conitnuously to maintain quality of the produced paper.
Optical characteristics such as brightness, whiteness, shade color and opacity help to monitor and control quality of paper as perceived by end users. Recording and monitoring of these optical parameters are necessary to optimize the material selection and processing conditions.
Brightness: Brightness is a measurement of light reflectance of a specific wavelength (457nm) of blue light.
Whiteness: Whiteness is a measurement of light refelctance across all wavelength of light comprising the full visible spectrum.
Opacity: Papers opacity can be briefly described as its ability to hide whatever is printed on its back side or on subsequent sheets.
International bodies such as TAPPI ( Technical Association of Paper and Pulp Industry ) and ISO ( International Oraganization for Standardization ) have standards for measuring Whiteness, Brightness and Opacity. These standard define measuring process and geometry of measuring instruments.
CM-3630 Benchtop Spectrophotometer produced by Konica Minolta is one such instrument having diffused illumination and zero degree viewing.This instruments meets ISO requirement of following measurements.
Shade Color: Paper's color can be specified based on the reflected light within the visual spectrum.
Shade is commonly measured on CIE Lab color space. CIE ( International Commission on Illumination ) is a France based international body.
Optional Opacity jig, makes Opacity measurement fast and easy. Computer based QC software helps to calculate CIE Whiteness and Yellowness index.