Research has shown that the two main ingredients in the ink, iron salts and tannic acid, each pose separate risks to paper, risks that are exacerbated by certain environmental conditions. The concentrations of the ingredients, the preparation method, the presence of other contaminates in the ink such as copper or zinc, the amount of ink that is absorbed into the paper, and even the type of writing instrument used, all influence and further complicate the degradation process. As a result documents that are produced at roughly the same time may exhibit a wide range of condition levels.

This variability is easily seen in the pages of manuscripts in which one page appears stable, while the adjacent page may show signs of severe degradation. In these cases it’s possible that the writer used a new batch of ink on the adjacent page or a new writing instrument, or even perhaps a new writer with a much heavier hand stepped in on the following page. It’s often impossible to say. These numerous factors, of course, complicate the role of the conservator, who must determine the best approach to treating and preserving collections.