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.