Pressboard (HD) manufactured by Cottrell Paper Company Cottrell pressboard - This material is made from 100% virgin fiber electrical Kraft pulp. The stock is extensively cleaned and specially refined to insure maximum purity and physical strength. No sizing, clay, fillers, or other chemical additives are used. - Pressboard (HD) manufactured by Cottrell paper company Cottrell pressboard - This material is made from 100% virgin fiber electrical kraft pulp. The absence of impurities ensures that the aging characteristics will meet the most exacting requirements.