the use of low specific gravity wood from thinning operations , for example , will produce a lower brownstock viscosity for a given kappa number target . a differential of 200 - cp falling ball pulp viscosity has been detected from kraft cooks of low and high specific gravity wood . using low specific gravity wood can reduce the bleach stage temperature and the chemical dose needed in the bleach plant to produce lyocell pulp specifications . low specific gravity wood also increases the ability to reduce pulp viscosity to very low levels without increasing the copper number of the pulp or the concentration of carbonyl in the pulp above acceptable levels .