The current deinking evaluation methods include image analysis (including manual and digital counting) and optical reflectance (using the Kubelka-Munk Equation). The mechanism of image analysis is simple that dark ink (mostly black) is isolated from the light background (fiber), and then captured visually or by digital devices. The image analysis methods have limits on their applications (e.g. cannot analyze newspaper) and ink speck size (only visible specks). Meanwhile, these methods have poor correlation with paper optical properties, and have large variances from sample to sample, side to side, etc. In this paper, an innovative approach, which employs a band of near infrared light and a digital imaging device, was applied to address these limitations. This approach has advantages for isolating specks from background and obtaining high quality raw data. This system also significantly reduces the variances among the handsheets and their sides. By using the ink elimination equation based on image analysis, the reliable ink elimination rates were obtained, and were also well correlated with paper optical properties. This system was also applied to newspaper deinking evaluation and shows positive results.
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