CONSERVATION
LEAFLET
February 2002
THE DANGERS OF HEAT -SEAL LAMINATION
Lamination is the process of sealing paper records between sheets of plastic, using heat and pressure. A document or book page is sandwiched between sheets of low-temperature plastic which has been impregnated with an adhesive. When heat and pressure are applied, the adhesive softens allowing the plastic to adhere and encase the document.
Plastics are made from petroleum products and they "off gas," causing a chemical reaction with the material sealed inside. Most often the adhesives used in lamination are also acidic. These factors combined with the heat used in this process act to speed up the acid reaction of the document or book page causing progressive deterioration and eventual embrittlement. Therefore, heat-seal lamination is ultimately extremely harmful to records. It is only appropriate for material with a short life expectancy and should never be applied to documents of historical or intrinsic value.
Document enclosures, folders, envelopes, etc. made of polyester, polyethylene, and polyurethane are "acceptable plastics". However, heat seal lamination using these products is still not recommended for historical documents due to the use of an adhesive and the heat required to melt the adhesive into the document. One principle of document preservation is that processes used to treat or mend items should always be reversible. Heat-seal lamination is not reversible. It is impossible to remove. Although it appears to offer physical support for fragile paper records, it does not extend their life; nor does it protect them from further deterioration. Eventually, it may be necessary to encase the laminated pages in inert polyester film to offer additional support.
Acceptable Methods of Preservation. Good storage conditions and proper environmental controls slow the acid deterioration of paper records, and proper handling techniques add further to their useful life. For individual documents/book pages of intrinsic value, polyester film encapsulation offers a good alternative to heat-seal lamination. Encapsulation uses chemically inert polyester, rather than plastic; the sheets are held together with double-stick tape applied around the edges of the document, rather than adhering to it. Information in fragile or deteriorating records can also be preserved on microfilm, if appropriate ANSI/AIIM standards are followed in its creation and storage. (See the ADAH technical leaflet "Preparing a Contract for Archival-Quality Microfilming Services.") Documents which have been laminated may be difficult to microfilm due to glare from the camera lights. For some materials, such as maps where the color key is vital to convey information, imaging may be the best reformatting tool. However, there are additional long-term preservation issues that need to be addressed with electronic information.
ADAH Government Records Division
P.O. Box 300100, Montgomery, AL 36130-0100
Telephone: (334)242-4452; fax: (334)240-3433
E-mail:
loverman@archives.state.al.us
ADAH web site: http://www.archives.al.state.us.