With the recent spate of tornadoes and the upcoming hurricane season it is time to think seriously about those backups and archiving tasks that you have been putting off. To help you get started I am posting an excerpt from the archiving chapter in my book Tell Your Story and Save the World.
When considering the archiving of personal or family historical records, photographs, and digital assets, it helps to establish a time horizon over which the archive will be expected to exist with a high degree of certainty. In this era, where Moore’s Law implies rapid changes in technology, five to ten years can feel like a long time. However, for archival purposes we may be interested in time frames on the order of 100 or more years. We can assume that, under normal conditions, most of the materials we take only reasonable care to preserve will exist intact in the shorter five to twenty year time frames, less so with longer terms of twenty to 100 or more years. If we were to estimate a probability associated with survivability in which we took into account a number of risk factors, we would expect to see some type of downward curve where the curve started heading toward zero somewhere out past the twenty year mark. This of course greatly depends on the materials in the archive but when we say “reasonable care” we are not applying typical archival standards. For example, a color photograph processed from a negative using standard processes in the 1980s will survive twenty to thirty years stored in a dark place and will most likely suffer some color degradation over that time period, subject to the chemistry in the dyes and environmental conditions. It is possible to scan such an image, correct the color change digitally, and output to a more stable image format provided the restoration is performed before unrecoverable color changes occur. The same image displayed in a frame and subject to daylight filtering through the windows in a room will degrade at a much faster rate, typically suffering both fading and color degradation. This image may be recoverable as well depending on the extent to which changes have taken place. If we then compare the archival stability of black and white photographs printed using traditional silver halide photographic papers, we will find that they typically have a much longer stability due to the fact that the image is constituted primarily of silver rather than the dyes typical of analog color processes. Degradation of black and white photographs most often occurs due to deterioration of and contamination by materials used for mounting or storing the image. Another source of degradation is the manner in which the image was processed initially, particularly insufficient washing following processing. Under reasonable care black and white photographs may be expected to have a lifetime well exceeding 100 years. Color images printed using more recent ink printing technologies may have color stability exceeding that of analog color prints. Additional factors such as type ink technology, presence of optical brightness agents, and the nature of the substrate used for printing are all factors in archival permanence.
There are many types of media which we may be interested in preserving. These include paper, photographs, analog audio tape, digital media in various forms, and objects of man made and natural materials.
Paper
Paper has a life expectancy that varies greatly with its manufacture. Low quality paper such as newsprint contains acid which leads to destruction of the paper over time. You have probably seen old newspapers that have yellowed and become brittle. Copies of such materials printed on acid free paper should have a much longer life. For large volumes microfiche or photographic microfilm provides a means of storing information contained in newspapers.
Photographs
Photographs may be printed via any number of processes onto a variety of substrates, all of which present various degrees of archival stability. Although manufacturers often publish expected archival lifetimes for their products one must take such estimates with a grain of salt. Those estimates are usually based on adherence to a specific processing recommendation that may not have been followed in the production of a particular photograph. For instance, a lab may have failed to replenish chemistry at a recommended rate or wash for recommended time. In most cases is nearly impossible to know whether such recommendations were followed.
Analog Audio and Video Tape
In the era preceding the development of digital audio and video the predominant medium for storage of audio and video data was the analog tape. This media was manufactured by depositing a layer of magnetic material onto a plastic film substrate. Recordings were made by altering the magnetic orientation of particles in the magnetic layer. The plastic substrates used tend to be reasonably stable, with lifetimes contingent on storage and environmental conditions. The magnetic layer is potentially subject to alteration by environmental magnetic fields, and may also be subject to failure of the coating over time. Aside from degradation due to such failures, additional risk exists due to the potential non-availability of equipment needed to read or play the material.
Digital Media
It would be impossible to articulate a comprehensive list of digital media simply due to the fact the field is constantly changing. In the transition from magnetic tape to disk based media we saw the implementation of digital tape followed by disks using the same coating technologies. This was followed by the hard disk and quickly thereafter with CD ROM and DVD media. Along the way we have seen pass by a few great ideas that didn’t quite catch on like the laser disk. There are also memory chip based media such as the USB stick, compact flash card, and the like.
We must also recognize that the Internet constitutes a storage medium as well. It has become a vast repository of photographs, social media interactions, discussion groups, and data storage solutions.
Each of these media types has an inherent expected lifetime. Recovery of data from failed digital media is possible, but tends to be very costly. The primary mitigation against risk of loss of digital media is the backup. A backup is a digital copy. Ideally, important data has at least two backup copies and one of those copies is stored where it is unlikely to be destroyed coincident with the destruction of the original.
Backups present two types of risk to digital data. The first is loss of the backup due to failure of the media. The second is what might be termed migration failure. Migration failure occurs when data is left on media that is either failing or subject to technological obsolescence due to cost or other factors preventing migration to new media. Thus, a backup exists, but accessing the data is difficult or impossible.
Survivability
Survivability refers to the degree to which an archived item remains intact, or in the case of an item that requires an intermediary interface, is readable or otherwise accessible. A book may deteriorate rapidly due to acid in low quality paper used in its publication. An audio tape may suffer loss of the magnetic coating, making it unreadable or only partially readable. In order for a material to survive we must account for the entire range of environmental conditions to which the material may be subjected as well as conditions relating to the makeup, chemistry, structure, or other characteristics which may contribute to its deterioration. For example, the failure to properly wash a black and white photograph during processing may result in deterioration of the image due to the presence of residual fixer. It is possible to test for this but the test may result in a stain on the print. Furthermore, it is a common practice to write on the back of photographs and preservation of this writing may limit preservation efforts. A solution might be scanning and output to a more stable medium.
Readability
Readability refers both to the quality of what is preserved in terms of the accessibility of information as well as the capability to access the information when in a non-directly accessible form. A directly accessible form is one in which no intermediary device or interface is required to view or access, such as a photograph or a book. An example of a non-directly accessible form is a text file on a computer floppy disk. Reading a floppy disk would require access to a disk drive of the correct type for the disk, which in turn would require a computer with an interface compatible with the disk drive. Lack of any component in this chain renders the data inaccessible.