Tuesday, October 23, 2012

Encapsulation: Too Close For Comfort

As part of a digitization project to scan historic maps of New Hampshire, selected maps are being reviewed here in the Conservation lab. Each week I gather fifteen maps from the Evans Map Room in Baker Berry Library and transport them to Conservation. Since the project workflow as a whole spans multiple departments in the library, a database with a listing of maps by call number is used for tracking. For each group of maps I can enter information about conservation review, necessary treatment, and their current locations.

For the past few weeks the majority of maps reviewed are in good condition and already encapsulated. Encapsulation is a great solution for flat items, small or oversize, especially if they might be handled often. There are two methods of encapsulation, welded and taped. Welded encapsulation is preferable, however, it requires specialized equipment, whereas the taping method can be done anywhere. Taped encapsulation is generally done with narrow, acid free double-sided tape and mylar. A reasonable margin should be given between edges of the item and the tape. A drawback with taped encapsulation is that over time an object can shift inside the mylar and come in contact with the tape. To avoid this, and the potential for damage, a wide margin between edges of the item and the tape is recommended. Whatever the method, welded or taped, once encapsulated objects are better protected from moisture and handling.

The rough edges on this map are caught in the tape. A wider margin would allow this map to float inside the mylar.

Tape will make a better seal if thread from linen backing are trimmed prior to encapsulation.

Items with folded edges should be flattened first, then encapsulated.

Written by Elizabeth Rideout.

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