Session	International Standards on Preservation of Information Recording Materials
Presenter	Peter Z. Adelstein Image Permanence Institute, Rochester Institute of Technology.
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ABSTRACT

The value of recorded information has become of increasing importance as materials age and data is lost.  This has resulted in a marked increase in standardization activities by the International Standards Organization. Today there are twenty-one published standards in this field, of which eleven have been printed since the paper on this topic at the Paris 2000 Joint Technical Symposium.  An additional ten standards are in various stages of development.  This paper is a review of the progress during the past four years and a discussion of current activities.

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PRESENTATION

Introduction

At the Joint Technical Symposium that was held four years ago in Paris, the status of standards on information preservation was given. During the intervening years there has been considerable progress although there is still a great deal of work to be done. This paper is a discussion of the more recent standards that have been prepared and will also outline the areas of current activity.

Standardization Procedures and Organization

Before discussing specific documents and the issues which are now being worked on, it is advisable to review the standardization process. Standards will only be acceptable if they are developed by a recognized organization with specific rules and procedures for their adoption. In the field of information preservation, the recognized body is the International Standards Organization (ISO).

ISO has its headquarters in Geneva, Switzerland and has a total membership of 146 countries. It is divided into 738 technical committees (TC), information preservation being the responsibility of TC-42. All voting is by member countries, with individual experts casting their ballot through their national standards body. For example, Canada is represented by the Standards Council of Canada and the United States by the American National Standards Institute. Twelve countries are active members of TC-42.

Technical committee TC-42 itself is divided into working groups (WG) and permanence is under the scope of WG-5. This working group is also subdivided into different task groups depending upon the subject matter. This organization of ISO is complex and so too are the balloting procedures. There are five different ballots which are required prior to the publication of an international standard. These multiple ballots all take place consecutively and consequently are very time consuming. However, they are essential to ensure that all interested parties have an opportunity to provide suggestions and modifications and that all negative ballots and comments are carefully considered.

There are four distinct types of permanence standards in WG-5 which are listed as follows:

Definitions. The single standard (ISO 18913) which defines terms is important so that specialists in various fields can communicate without ambiguity. Common definitions have been agreed to by representatives of the photographic, magnetic tape and optical disc fields.

Test Methods. These documents are necessary to ensure that material properties are measured by standard, meaningful and reproducible procedures.

Specifications. These standards list the test methods and the required property levels for a recording material to be given a “life expectancy” value. Some specifications may also describe the required test methods if a separate test method standard does not exist.

Standard Practices. These documents describe recommended procedures for the storage, care and handling of recorded materials.

WG-5 has responsibility for the permanence and preservation of six different types of recording materials, namely photographic plates, films and prints, digital hard copy prints, magnetic tape and optical discs. The number of standards that have been published has increased dramatically. In 1945 there was one ISO standard, at the time of the last JTS meeting in Paris 2000 there were 10, and today there are 21 with 11 additional standards now being developed. Identification of these ISO permanence standards has been facilitated by being assigned a number in the 189xxx series.

The main thrust of this paper is to update the standards activity for the past four years. It is not practical to give a meaningful presentation of the eleven new standards published during that time, not to mention the eleven that are now under development. Therefore this discussion will be confined to describe the activity in four main areas, namely digital color hard copy, magnetic tape, optical discs and storage recommendations for multiple media. These four fields represent technologies in which there is a very high interest level by archivists, librarians and general consumers. Each is discussed in turn.

Digital Color Hard Copy

This refers to the color prints produced by computer/printers. The number of prints created by this ever growing market has increased dramatically in recent years. Consequently concern about their life expectancy has also increased. Currently three different technologies are being investigated, namely ink jet, dye-sub and electrophotographic. The issue is much more complicated than exists for regular photographic images. With the latter there is a general similarity between different products and each material encompasses both the image and the paper support. This is not the case with digital hard copy. For example with ink jet material, the paper support may be “swellable” in which the colorants are embedded in a matrix, or the colorants may be held by a “porous” matrix coated on the paper. In addition, the colorants may be either dyes or pigments which have very different properties. There are also many manufacturers of either colorants or papers. Consequently there are many possible combinations of colorants and paper supports. This has made the need for a print life specification all the more critical so that a specific colorant-paper combination can be evaluated.

Since 1997 representatives from ink, paper and printer manufacturers as well as librarians, archivists and testing laboratories have formed a task group which has been meeting semi-annually to address this need. Attendees number about 50 which is an unusually high number of participants in a standards meeting.

The preparation of a material specification is a complicated process and involves the following four steps.

• The pertinent properties that could limit the permanence of the material must be established. For color images this includes any fading of the individual colors as well as any increase in stain. Sometimes uneven color fading is more critical than if all colorants faded to the same degree. This results in a shift in the color balance. These properties are common to both the traditional color photographic images as well as digital hard copy images. However, the latter also have the possible additional complication of lateral movement of dyes creating image blurring, or the transfer of dyes to adjacent surfaces. To date measurement techniques have been fairly well established for these properties.
• Test methods must be standardized for the aging and environmental factors which may cause image change. The ISO task group has agreed that test methods are required to standardize the effects of dark aging, light exposure, air pollutants, humidity, water fastness and fingerprints. The test for water fastness has been standardized and good progress has been made on the procedures for dark aging and the conditions to evaluate the effect of light. Considerable work is required on the remaining four factors.
• A specification on permanence requires procedures which evaluate the effect of time. In other words, once a test method is established, the conditions must be exaggerated in order to predict future behavior. For example, this involves using elevated temperatures or high light levels. It is essential that the severe conditions show changes in finite time that will also occur over longer periods under milder and more realistic conditions. Otherwise the accelerated tests have no practical significance. This has proven to be a difficult aspect of writing a permanence specification but dark aging and light effects are close to finalization.
• Once the accelerated test procedures have been established, there remains the problem of deciding what is an acceptable level of change. This is very subjective since it is very dependent upon the nature of the image. For example a greater change would be tolerated in a circus poster than a Monet painting.

Magnetic Tape

The situation with magnetic tape is more complicated and less satisfactory than with digital hard copy. To obtain maximum data compaction, magnetic tape is very thin and consequently it is relatively fragile. Moreover, in tape recorders and players, magnetic tape is transported from hubs and reels over rollers and magnetic heads in a wide variety of configurations. The net result is that tape life is usually controlled by physical failure, and this physical failure can be manifested in many ways depending upon the format, the recording device and the playback equipment. A critical feature in magnetic systems is the close spacing between the magnetic head and magnetic medium. This is required for optimum output, but it causes head wear, binder wear, or both. In some situations, tape fails by binder debris clogging the magnetic heads while in others it may be due to high friction and the resulting lack of uniform transport. The task group involved with this material recognized that the critical physical properties are binder cohesion, binder-base adhesion, friction, clogging of magnetic heads, dropouts, and binder hydrolysis. Magnetic properties of interest are coercivity and remanence. These decisions in general were consistent with conclusions from individual investigations. Test procedures for adhesion, friction, and hydrolysis were agreed to, but cohesion, head build-up, and dropouts are difficult to measure requiring extensive development work. The latter is also very system dependent.

To standardize appropriate test methods for these properties requires considerable laboratory studies by a well equipped laboratory with experienced staff. This necessitates the participation of tape manufacturers. Unfortunately, involvement by tape manufacturers had decreased to the point where there is no longer a critical mass to prepare a magnetic tape specification standard. This lack of activity may possibly be due to the general acceptance that magnetic tape has a limited life expectancy. However, it is in the best interests of the consumer community to prolong tape life as long as possible. Consequently representatives from libraries, archives and a disaster recovery laboratory were able to prepare two standard practices documents which are based on their practical experiences.

The first standard was published in 2000 and covers recommendations for tape storage. This includes not only the appropriate temperature and relative humidity storage environment, but also addresses the topics of tape preparation prior to storage, monitoring during storage, the storage room, the housing, and enclosure materials such as reels, cassettes, cartridges and containers. The second standard deals with the care and handling of magnetic tape. It is expected to be published very shortly. Topics covered include a description of problems associated with the integrity of the tape pack, contamination concerns, handling techniques, tape inspection, tape cleaning, and disaster recover.

A major concern in the recovery of information on magnetic tape is the preservation of the necessary hardware and software. This is an area where standards have not been written and work is not planned. Unlike photographic products, these materials can only be machine read, and the problem this poses has been recognized for many years. As equipment is used, parts wear out and must be replaced. Equipment repair is only possible if components are still manufactured or can be cannibalized from other equipment. If past history is any guide, the hardware will become obsolete within a relatively short time. Systems in this field are undergoing constant change, and it is very doubtful that replacement hardware will be available after several decades.

In the face of the continued evolution and consequent obsolescence of playback hardware and software, consumers might wish that the ISO standards committee would create a single readability (i.e., hardware-software) standard that all future electronic products must adhere to. However desirable this approach may be from a storage prospective, it is not practical in the long term because it would inhibit the development of technology, would retard improvements, and would never be supported by the manufacturers.

Optical Discs

Within the last 20 years there has been the development and explosive growth of information distribution and storage using optical disc technology. These materials have been designed in many configurations and for many applications. However, all share the common characteristic that they are read by light and are only machine-readable. Standardization activity was also started in 1989, at the same time as work on magnetic materials.

Unlike magnetic media, optical discs are manufactured not only in a variety of sizes, but they can also be composed of very different materials. The most common substrates are either polycarbonate or glass. The image recording layer features various organic or inorganic coatings since they function by several different mechanisms. For example, write-once discs can record information by ablation of either a thin metallic layer or a dye/polymer coating, by phase change, by metal coalescence or by change in the surface texture. Read-only discs have the surface modulated by molding of the polycarbonate substrate, and erasable discs are based on magneto-optical or phase change properties. Despite this vast dissimilarity in composition, optical discs have an important advantage over magnetic materials with respect to predicting their life expectancy. Optical discs are recorded and read by light and do not come in contact with moving or stationary parts of equipment. Therefore their useful life is mainly determined by the properties of the material itself, and, unlike magnetic tape, physical wear and tear is less of an issue.

Since chemical changes of the disc material are likely to be dominant in many situations, standard incubation tests have been published for three disc types; CD-ROM, MO and CD-R. However, these are test methods only, not disc specifications. These three standards only predict the effect of temperature and relative humidity on chemical stability. They are not specifications since they do not cover disc failure caused by warping, changes in the reflecting layer by corrosion, cracking or pinholes, changes in the reflection of any dye layers by light, pressure or crystallization, or breakdown of the disc laminate by adhesion failure and layer separation. The test methods are only valid if the dominant failure mechanism at the accelerated conditions in the test method is the same as during usage. It also does not address material changes due to light, to exposure by corrosive gases or temperature and humidity cycling.

These three test methods are of primary benefit to manufacturers or sophisticated testing laboratories. They do not help the consumers who are concerned about the life expectancy of optical discs. However, preparation of an optical disc specification involves the same problems as experienced with magnetic tape. Additional test methods would be required as well as methods to accelerate changes and to establish end points. This necessitates the involvement of laboratories who are experienced in this field and these would be primarily facilities of disc manufacturers. However, the manufacturers have not become involved in this standard activity. This would require a considerable commitment of technical resources. Another factor may be the realization that preservation of information on optical discs may be more dependent on the availability of the required software and hardware than on the life of the medium. This is the same problem that was previously discussed for magnetic tape.

As with the magnetic tape users, the optical disc consumers have a need to prolong the life of their discs as long as possible. Consequently the consumers on the ISO task group have prepared and standardized a document on disc storage. This ISO standard was published in 2000 and covers many of the same topics as in the corresponding magnetic tape storage standard. Included are recommended temperature and relative humidity and problems associated with gaseous pollutants, magnetic fields, light, dirt and humidity cycling.

Another consumer oriented standard on the care and handling of optical discs is currently being prepared. This document will discuss recommended handling techniques, contamination problems, disc transportation, disaster recovery, inspection and cleaning. It is expected to be completed within the next two years.

Multiple Media Storage

The ISO permanence standards include six publications on the recommended storage environments for different types of materials. The recommendations differ from each other because the different media have different susceptibilities. For example, historic photographic glass plates can exhibit adhesion failures due to humidity cycling while both cellulose acetate film support and photographic color images are adversely affected by elevated temperatures and humidities. The storage standards for the latter specify three recommended environments for each material, permitting a high storage temperature with a lower storage humidity. On the other hand, black-and-white photographic images on polyester support are very stable and do not require stringent environments. All these standards are technically sound as they apply to a single material.

While some collections consist primarily of a single medium, many archives and libraries have the problem of storing a wide variety of materials. It is not practical in these situations for institutions to have different storage areas which are optimized for each medium. Moreover, most record centers organize their storage areas by subject matter and not by the medium type. Consequently compromises on storage conditions must be made. This is the practical situation that exists and it has recently been addressed by the ISO working group 5.

A standard is now under preparation which proposed a compromise of four storage environments. This document indicates the permanence behavior of twelve different materials in each of the four environments. This will enable the curator to evaluate the consequences of the storage conditions that are chosen. Also discussed are the effects of temperature and relative humidity cycling. It is expected that this standard should be completed by 2005.

Summary

In recent years there has been a great deal of activity in the preparation of ISO standards on the preservation of recorded information. Approximately 60 individuals have been meeting semiannually in this endeavor. This involves a very considerable commitment of manpower and resources. It has resulted in eleven new standards that were published within the last four years and an equal number now under development.

The reason for this intense effort is twofold. As materials get older, the information becomes more valuable while at the same time incidents of lost information become more numerous. In addition, the tremendous increase in the variety of materials used to capture images and information has made these problems more acute. The problems facing the archivist, librarian and curator today are much more complex and serious than existed just a decade ago.

Major areas of study have been the permanence of digital color hard copy, magnetic tape, optical discs and storage environments for multiple media archives.

 

 

SPEAKER BIO

Dr. Peter Z. Adelstein
Dr. Adelstein retired in 1986 as Unit Director in the Eastman Kodak Co. and since then has been a senior research associate at the Image Permanence Institute at Rochester Institute of Technology. He has published over 75 papers on brittleness, dimensional stability, film base, chemical stability, storage behavior and stability standards of plastics, gelatin, photographic film, and magnetic tape. He is chairman of the International Standards Organization group having responsibility for preparing standards on these topics.