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7. Storage and preservation

Storage of paper

Although a reduction in the quantity of paper being circulated and stored is often a motivating factor in the introduction of microfilm or document management systems, it is usually impossible to eliminate it entirely. Many thousands of pages may have been accumulated in archives and reference is often so infrequent that it would be uneconomic to film or scan them and incorporate them into an active EDM system. Some sort of retrieval system will already exist for such files with pages held alphabetically, numerically or by date and that index can be incorporated into the EDM system with links to the location of the relevant files.

Many service bureaux and some specialised storage facilities offer low cost secure off-site storage for such documents and most can provide a retrieval service to scan and transmit any required document on demand. When documents have a specific life arrangements can be made for their certified destruction after the expiry date. On this site we list UK facilities in our services section under Secure storage facilities and Certified destruction but we only include facilities that also offer secure storage of film and computer media.

Storage on microfilm

In many areas microfilm has been overtaken by electronic document management techniques but it remains supreme as a long-term storage medium.

There is a sound case for film being employed as a back-up to any electronic archive. This reflects growing concern that rapid advances in computing technology may necessitate the frequent conversion of archives held in outdated software formats or on magnetic media for which reading equipment is no longer supported. UK service houses offering microfilming of office documents and large formats such a maps and plans are listed in the services section of this site.

Some companies already have large collections of information on microforms which they would like to access via an electronic document management system. Most UK companies offering film scanning will be found listed alphabetically in the Services section of this website. Careful consideration is essential before deciding to scan the entire microfilm record content because, if references are likely to be relatively infrequent, it may be preferable to buy a suitable low-volume reader-scanner and scan specific images when they are needed rather than pay for the conversion of the whole archive.

Storage of digital data

Document scanning creates massive demands for digital storage but modern computer systems can now cope with volumes that would have been impractical only a few years ago. It is nevertheless often pointless to hold old digital files on internal on-line storage and service facilities have been developed to act as digital data warehouses, able to maintain and store vast quantities of digital data and provide any file on-line in seconds. The web is also  being increasingly used to hold files and make them accessible to internal and even external users if confidentiality is not a factor. 

Other methods of holding large quantities of digital data off-line include transcription to microfilm using COM.  UK companies offering COM (computer output on microfilm) facilities are included on this website under Services.

Suitable storage facilities for microfilm

Most microfilm systems preserve their master films from contamination and damage by holding them in secure storage and using duplicate film for reference. Copies are usually diazo or vesicular duplicates and they are tough enough to withstand frequent use. Storage conditions for master silver-halide film determine its life expectancy but an anticipated life of up to 500 years for silver-gelatin film that has been correctly processed and stored at around 20 degrees C in a Relative Humidity of 50% or less, thermally processed silver film has a life expectancy of 100 years.

Storage conditions determine life expectancy and for silver gelatin film. A Relative Humidity of around 40% is good with a maximum of around 50%. At an RH of 60% fungus growth may be a problem. Film is best stored in fireproof cabinets or safes and silver gelatin film can withstand 120 degrees C, diazo can stand 90 degrees C and vesicular 70. In case of flood, film can be rescued if it is kept wet and taken to a suitable laboratory. If allowed to dry the layers can adhere to one another. Film containers should be air and water tight and silica gel or charcoal can be inserted to combat humidity.

Film should be inspected periodically and any smell of vinegar is a cause for concern. This problem only relates to silver gelatin film on an acetate base and only affects film produced prior to the introduction of a polyester base in the mid 1980s. The smell is caused by the breakdown of acetic acid and affected film can deteriorate rapidly to the point of becoming unreadable so this is a serious matter requiring prompt attention. Affected film can become very brittle and it should not be used in a reader as it is prone to heat damage.  If the vinegar smell is very strong it may be too late to save the film, but deterioration can be partly arrested by storage at below 10 degrees C in RH of between 20-50%. There is no actual cure, but the old remedy was to make a copy of the affected film on modern polyester base material. Today it is more usual to scan the images and store them digitally. The problem is contagious so it is best to separate all affected acetate base film from the main film library, inspect it and store it well away from any that is still in good condition.

Whatever method of storage is adopted, an agreed policy must be established to determine how each document type will be handled at each stage of its life-cycle. Strict compliance with such a written policy is an important factor in determining whether a scanned or microfilmed document will be accepted as legal evidence.

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Content

1. Introduction

2. Microfilm today

3. Getting started

4. Input and Output Methods

5. Indexing and retrieval

6. Management and control

7. Storage and preservation

8. Hybrid systems

9. Services available

10. Standards

 

Webmaster: Gerald Baker     Last update 8/4/2018     G G Baker & Associates 2018