REFLECTANCE BASED INK CONTENT MEASUREMENTS • OPERATIONAL WAVELENGTH COMPARISON BETWEEN 700 nm AND 950 nm, 2011 PEERS Conference

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Analysis of small-sized ink in paper recycling is commonly based on ERIC (Effective Residual Ink Concentration, 950 nm) and RI (Residual Ink, 700 nm), which are obtained from the corresponding reflectance values and scattering coefficients. According to the ERIC method, the scattering coefficient should be measured. Use of a constant value for the scattering coefficient remains an equally common practice, although some previous studies have shown that uncontaminated fiber fines and fillers improve the scattering properties of pulp at the wavelength of 700 nm. In this study, optical properties were studied at 950 nm and compared to those obtained at 700 nm using an undeinked sample, samples floated to various degrees, and a hyperwashed sample. It was seen that changes in the fine material content affect the scattering coefficients when measured at 950 nm and for this reason the scattering coefficient should be measured during the ERIC determination. Nevertheless, the range of scattering values measured was smaller in comparison with that obtained at 700 nm.