5 DISCUSSIONS

From the PAT results on the various papers, it seems appropriate to recommend that nonbuffered papers in direct contact with photographs be made only from cotton or fully delignified pulps. It also appears that there is no significant benefit to using cotton pulps over the less expensive, fully delignified wood pulps.

It also appears from the PAT results that photoinert buffered paper enclosures can be made from semipulps as well as from cotton or fully delignified pulps. However, semipulps are not delignified to any standard or predictable value, and therefore actual lignins content will vary. Although these results indicate that some enclosures made from semipulps may be suitable for use in direct contact with photographs, great care should be exercised in their selection. Fully delignified papers are preferable because of reduced risk of gelatin staining.

For the time being, the discussion of whether the harmful effects of lignins-containing papers come from lignins or the extractives is moot. The extractives are removed in direct proportion to lignins during pulping. Differentiating the reactivity of the two may become more important during further investigations of the photo-reactivity of semipulps.

From the box test results, it appears that the PAT may be too strict for some box materials. The air space in the box does somewhat mitigate the harmful effects from the high-lignins boxboards. The test results, however, do not answer questions about how these effects might vary as box volumes change or how the boxboard might affect photographs when the box is filled. There is also the possibility that the inclusion of an alkaline reserve in the boxboards may reduce these harmful effects enough to pass the box test. So, until further research can be performed, storage boxes, slipcases, and album binders should ideally be made of the same quality paper products as enclosures intended for direct contact with the image.