Alkaline Buffers
A generally accepted level of alkaline
buffer added to paper intended for archival use is three to five percent. There
are exceptions to the inclusion of alkaline additives, particularly with regard
to papers meant for the preservation of certain protein based textiles and
photographic materials, but we will address this issue later. Typically the
alkaline buffer used in paper is calcium carbonate (CaCO3). Remember, an acid
is any substance which can donate a proton, and we have seen the havoc a proton
can inflict upon the bonds holding our paper together. A base, such as calcium
carbonate, is any substance that accepts protons. The negatively charged
(basic) hydroxyl unit (OH) combines with the positively charged (acidic)
hydrogen ion (H) to form water. Assuming enough alkaline buffer (calcium
carbonate) is available, the potential exists for the acid to be neutralized
before it can damage the paper. This is why it is important to have alkaline
buffering in all paper products used in conservation except, as mentioned
earlier, those intended for use with certain protein-based textiles and
photographic materials where excess alkalinity could potentially cause
problems.