Brightening of mechanical and high-yield pulps

This work lays out the general principles of the brightening of mechanical pulp. The author presents a practical discussion of the brightening processes for both reductive (sodium hydrosulfite or dithionite) and oxidative (hydrogen peroxide) chemicals. Each of these chemicals has its advantages, disadvantages, and most suitable applications. Chemical preparation is different for each of them, as is the method of application to pulp. The differing chemistry of the brightening agents affects how they should be stored, prepared, and applied for best results. Also covered is multistage bleaching, with various combinations of chemicals for different results. The chemistry, likely problems and solutions, alternative application methods, conditions, and alkali sources are discussed and reviewed with respect to situations where they might be beneficial and when they should be avoided.