Overbeaten refers to fiber that have been "emascerated" for long periods of time. Whenever fibers are broken down for paper-making, this process is referred to as "beating." When fibers are beaten for periods longer than required to make simple paper, this is termed "overbeating." Fibers that have been overbeaten are incredibly short and dry to form a rigid and stiff structure. Paper made from overbeaten fibers is used very successfully in paper-based sculpture.
