Influence of Colored Papers on the Brightness of Ledger Pulps, 1993 Pulping Conference Proceedings

Ledger grade materials often contain color which must be removed in order to make decolorized secondary fiber pulp for the production of high brightness recycled products. The intensity of color and the quantity of colored paper present in these materials very widely. The brightness of a deinked pulp is significantly influenced by the presence of colored papers. Conventional ledger deinking systems are often limited by the technology to produce economically acceptable quality deinked pulps from furnishes containing high amounts of colored papers. The purpose of this work is to understand scientifically the color components of a ledger furnish and the role they play to influence the brightness of ledger pulps. The color content of a paper, which is characterized by the three fundamental qualities “value”, “hue” and “chroma”, is used to analyze the direction and magnitude of color between a sample and a white standard. The results showed a definite influence of color on brightness of ledger pulps. This color-brightness analysis developed can be used to optimize a deinking system for the production of high brightness products.