A CONSERVATION COLUMN

by Cynthia Ball

Q: What documents should be encapsulated? Does one have to be a conservator to do encapsulation? Should encapsulated documents be hermetically sealed?

Encapsulation creates a reversible storage capsule which offers some protection from physical handling for some records. Two sheets of Mylar Dupont Type D and Scotch 3M #415 double-sided tape are used to encapsulate individual records. A special polyester welding machine may be used to seal all four sides of the capsule instead of tape.

Documents which may be encapsulated include manuscripts, maps, and plans. Records with friable media, such as charcoal, chalk, pencil, or pastel should not be encapsulated because Mylar creates an electrostatic charge which will draw friable media away from the paper support. also, records which are attached to warped backing boards or showing signs of mould growth or attack from insects should not be encapsulated. Encapsulation is not recommended for photographs adhered to poor quality secondary supports or for contemporary color photographs.

One does not need to be a conservator to do encapsulation. However, some precautions need to be taken. Consult Canadian Conservation Institute Note 11/10 or a publication such as Preserving archives and Manuscripts by Mary Lynn Ritzenthaler for detailed written instructions which are enhanced with drawings.

Thhere is increasing evidence that documents sealed within a Mylar film capsule without prior deacidification exhibit an increased rate of deterioration because a micro-environment is created inside the package. The advantages encapsulation provides may override this concern. A gap may be left at the four corners of the package or the decision may be made to have the tape meet at the four corners. This is a matter of personal preference. It was formerly felt that air holes at the corners permitted the escape of degradation products, but this has been disproved by research at the Library of Congress. The gap does allow air to escape, eliminating puckers at the corners.

The acceleration in the decline of physical properties of some acidic and neutral papers can be eliminated by enclosing another sheet of paper containing an alkali reserve in the same encapsulation package. Like any other treatment option, encapsulation should be undertaken after considering the individual requirements of each object.