Thank you for your questions concerning preservation. Contrary to popular belief, neither polyester film, nor polyethylene or any other plastic film is in itself conducive to the longevity of paper - except from a short-term perspective. The benefit from "encapsualtion" between two sheets of a clear plastic film, derives largely from the protection that this practice provides from potential injury to the object from physical handling. Encapsulation may also protect objects from water damage in the unlikely event of a water sprinkler going off in a fire situation.

Our most current understanding of the aging of paper is that it loses strength and suppleness and ultimately becomes brittle due mainly to acid hydrolyitc degradation caused by formic and acetic acids that are produced constantly within it. These acids continue to accumulate making the paper increasingly vulnerable to the aging process. The adverse effect of these acids can be reduced by

1. lowering the temperature and the relative humidity under which it is stored so as to minimize the dissociation of these acids (these acids are harmless in their undissociated state),
2. by sandwiching the object between two sheets of paper or board with a high alkaline reserve so that these acids would be absorbed and neutralized by the alkaline paper or board, and
3. by a chemical treatment that will not only neutralize the acids, but also provide an alkaline reserve that would continue to protect against acids that will form in the future.

Encapsulation by itself can be actually harmful because it does not let the acids formed within paper diffuse away, but instead enhances their accumulation. In laboratory experiments carried out under elevated temperature and relative humidity conditions, under which these acids should diffuse more easily, even test papers placed inside L-sealed polyester envelopes (sealed along only two of the four edges) tended to age at a rate comparable to that obsrved for test papers aged within fully sealed envelopes. On the other hand, a backing of an alkaline matboard within a polyester film envelope or capsule, or inside a picture frame, has been shown to provide a more beneficial environment. The difference in the latter approach is that the alkaline backing can act as a sponge to soak up acids.

However, for the most brittle paper objects which may be too delicate to handle, encapsulation does provide much needed support and reinforcement to enable their handling while preventing physical damage. That is the only circumstance in which I would encourage encapsulation. Even in such a case, it would be preferable to support the object first an alkaline paper or board. Unfortunately, this last option may not be available for manuscripts or other objects that need to be viewed from both sides.

One effective and functional approach to store a manuscript for the long term may be to interleave the individual sheets comprising the mauscript with alkaline paper and insert this package within an alkaline folder. A photocopied facsimile of the manuscript can be placed within a clear polysester jacket attached outside the folder to show what is inside. Whenever it becomes necessary to handle the manuscript, the photocopy can be pulled out of this jacket and manipulated rather than the original.

In terms of using dessicants, we do not recommend them for long term use or storage, mainly because they would have to be constantly changed, once they have absorbed the moisture and treated to remove the moisture before they can be returned to the storage area to again become saturated with moisture and then again be treated to remove the moisture. They work great for short term solutions such as exhbition cases, etc. I would recommend the use of a dehumidifier in the room where the objects will be stored. Even a small dehumidifier will in the long term cost less then the amount of dessicants needed to maintain good environmental conditions.

Thank you for your interest in preservation.