What Are the Different Types and Formats of Microfilm?
Microfilm consists of a layer of emulsion coating embedded in a base of either cellulose (usually acetate or triacetate) or polyester. Polyester-based film is stronger and more stable than cellulose, absorbing less water and drying more quickly after processing. It is the only base acceptable for preservation microfilm and has a life-expectancy rating of 500 years. There are several common types of microfilm, each with a different purpose. An agency may employ more than one type in its microfilm program. Silver-halide film produces images of high quality and is used universally for original camera negative (first generation) microfilm. Its potential life-expectancy rating of 500 years makes it the only film suitable for archival records. Silver-halide film has rigid environmental requirements, however, and deteriorates rapidly if exposed to high temperature or humidity, chemical agents or pollutants, or frequent handling. Its primary use is as a security copy of the records, from which
