They may also serve as buffering agents to make paper less acidic. Calcium carbonate and magnesium carbonate are the most commonly used fillers. Whiteners, like titanium oxide, also end up in the spaces between fibers, but their specific purpose is to create a brighter finished sheet. While most paper fibers are benign in their health effects, many chemical additives are not. Powdered pigments, in particular, can be quite toxic and, once airborne, are easily inhaled.
Many additives are poisonous if ingested.
Certain ones can also cause rashes and other skin reaction on hands and arms dipped into the vat. Because of the variety of additives available, the hand papermaker is urged to research the subject carefully. Further reading is recommended. Copyright 1992 Hand Papermaking, Inc.