What Can We Do to Protect
Paper From Acids?
Insist that
the paper you use be made from high quality fibers (preferably, alpha-cellulose)
without alum-rosin (acid) sizing and with a maximum 30 parts per million of
iron and .7 parts per million copper. Specify and use papers that are free from
lignin. Lignin is a very large complex organic molecule which binds the
cellulose together in a tree. While a papermaker can increase his paper yield
per tree to 95% by using the lignin (as opposed to 35% maximum for pure
cellulose), the lignin will greatly hasten a papers demise by breaking down in
myriad different ways to yield many different acids and peroxides (which can
also damage photographic materials). A commonly used qualitative test for
lignin is the Phloroglucinol (1,3,5-Benzenetriol) test. This test was designed
to indicate the presence of lignin in quantities of 6 percent and higher. Since
even small amounts of lignin can cause significant problems, you should not
rely on this test. A quick visual clue to the presence of lignin is the color
of a paper or board. The brown kraft color of standard (and some acid
free) shipping and packing containers comes from the lignin in the
paper. This same lignin produced color is often seen in the center portions of acid
free solid and corrugated boards, so you should exercise caution (or
preferably switch to lignin free materials) if you are using products made from
these types of boards. Apparently, some time ago, some people were taught that
lignin was present only in ground wood (mechanical wood) pulps. This, of
course, is not true. While mechanical wood pulps do contain lignin, unbleached
(brown) kraft pulps such as those produced in vast quantities in the U. S. for
corrugated shipping containers and kraft wrapping papers also contain
essentially their full original complement of lignin. As mentioned, mechanical
wood pulp products such as those commonly found in newspapers, pizza and shoe
boxes, and low quality mat/mounting board also contain lignin. Some papers are
available which are partially or semi bleached. These papers and
boards are a lighter brown color than their unbleached counterparts. However,
they still contain lignin. Our Lig-free Type I paper and boards are fully
bleached alpha cellulose which we have dyed a pleasing light tan color with
special fade and bleed proof dyes to mask any soiling which may occur with extended
use. These Lig-free papers do not contain lignin.