ABSTRACT
In this chapter we will consider general aspects of the archival or life expectancy of different imaging media. Previously the term archival was used to describe materials with a long life, which is now taken to mean a minimum of 100 years. The new electronic media have expected lifetimes of less than 100 years and it is now generally agreed that the term archival be substituted by the term life expectancy. All materials degrade over time and differing imaging media are subject to many causes of degradation, many of which are now well understood. Steps may be taken to ensure that their life expectancy is as long as possible. As imaging systems advance and new systems evolve the initial prime criterion is to provide a system that works and fulfils the needs of the consumer. In these initial stages of providing new products their longevity is not necessarily a high priority. This was the situation at the start of the negative-positive photographic process when W.H.F. Talbot experimented with various fixing methods to achieve a stable image and this approach continues to this day. However, as our knowledge advances, both manufacturers and users are more aware of the need for imaging media to have reasonably long life expectancies and much research is undertaken to achieve this. This may then become a useful strategy in marketing imaging products. A recent example is in colour hard copy output using ink-jet or thermal dye-diffusion systems in which the early products had very poor stability to light, as did colour photographic print materials before them. This problem has been researched thoroughly and more recent products have much improved light stability.
