Still the Top Choice for a Preservation Medium
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A respected librarian expands on the reason why and suggests how to go for 1,000-year safe storage.
Microfilm seems, to many, outdated and behind the times. In our computer-driven electronic imaging must, surely, be the way to go… to preserve information for posterity. I disagree, and here’s why microfilm is still my choice of preservation medium for any information that needs to be around for a long, long time.
Microfilm possesses two simple advantages over most other media used for recording information: it is long-lived and readable by humans. These are pretty basic attributes but they are also crucial…..
Proponents of electronic imaging make keeping up with advancing technology sound easy. One simply “refreshes” the files, transferring them to the latest version in order to assure that the data are not lost. I worked in a large university library and the prospect of transferring our collections from one format to a new one was daunting.
If your collection consists of a small number of files perhaps you could contemplate redoing them every few years, but for collections of any large size it’s close to impossible. Furthermore, I suspect that in many cases people would forget to do anything until it was too late.
The 1,000-Year Medium
Microfilm, on the other hand, is a medium proven capable of lasting more than 1,000 years, given reasonable care. And, equally important, the information on microfilm can, in a pinch, be retrieved with an instrument that has been around for centuries and (likely) will continue to exist for as long as humanity exists – a magnifying glass.
Microfilm is available in a number of types and it’s important to differentiate among these. Each type suits the purpose for which it was manufactured, but I have found that many people fail to understand the difference between film types. As a result they may choose the wrong film for their application…..
It’s important for the consumer to be educated about each type. By choosing the appropriate film, and by being aware of the hazards to the longevity of each type, users can assure themselves of a successful outcome.
Technical Report for information and Image Management – Preservation of Microforms in an Active Environment – Guideline, ANSI/AIIM TR13-1998, of which I was the primary author, is published by AIIM International. It gives basic information needed to make an informed choice of film type…..The following information is taken from that report and I urge anyone responsible for a microfilm collection to get a copy…..
Only One of The Big Three Is the Preservation Choice
Three types of microfilm in most common current use are silver halide, diazo and vesicular. Of these only silver halide is considered by the preservation community to be suitable for preservation purposes…..Only silver halide film on a polyester base, processed and stored in accordance with existing standards, has been proven to be capable of lasting more than 1,000 years…..
Most films used to create a microfilm original (camera films) are silver halide…..Silver halide film is quite resistant to heat and light unlike its two main (duplicating) alternatives (diazo and vesicular). These differences are important for preservation considerations….The main weakness of diazo film is that the images ultimately fade, even in dark storage…..
Vesicular is sensitive to pressure damage and can be easily scored by dirt on a reader, leaving what look like scratches. Also, if it gets too hot, the tiny bubbles (or vesicles) that make up the image burst and the image is gone…..Many film readers reach film gate temperatures beyond the resistance limit of many vesicular film…..In libraries, patrons often forget to switch off the readers and wander away, leaving the film to bake. After a few hours, if the film is diazo or vesicular, the images in the area exposed to the light and heat may be gone…..
Proper storage is crucial to the longevity of all film types, but this isn’t difficult to achieve…..Temperatures for extended-term storage must not exceed 21°C (70°F) and the relative humidity range must be 20-50%.....ANSI/AIIM TR13 1998 explores these topics in detail and explains how to store films correctly and how to inspect them for signs of deterioration…..
Reprinted From:
MICROGRAPHICS & Hybrid Imaging Systems NEWLETTER
