Gel permeation chromatography (GPC) is used as a method of measuring the change in the degree of polymerization caused by hydrogen peroxide bleaching. Five fibers were tested: contemporary cotton linters, bleached flax and semi-bleached kraft; bleached flax from 1899, and bleached mixed fiber from 1874. The hydrogen peroxide (2%) bleaching baths were buffered to pH of 8, 9, and 10. Conclusions indicate that contemporary rag samples underwent less degradation than old rag samples or wood pulp. The variation in pH did not seem to contribute to results. See AATA 19-956.