Sodium-based hydrosulfite is also very effective in bleaching recycled pulp because sodium hydrosulfite provides powerful reducing agent and can effectively react with the dyes in the pulp. Also, Most recycled furnish usually contains some mechanical pulps which is capable of being bleached by sodium hydrosulfite. The bleaching conditions for recycled pulp by sodium hydrosulfite are very similar to those for mechanical pulps. If such contains, The furnish mainly chemical pulps, As mixed office waste, Significant brightness gain could be achieved by performing a hydrosulfite y stage at a much higher temperature, 80 100 c and at ph of 7. 0.