Terminology

Jennifer Barnett <reginatextilia [at] orange__fr> writes

>During a current revision job, I was confronted with the term 'life
>expectancy' applied to paper archive objects and set to searching
>for an accurate alternative for this incorrect term: objects are not
>alive. Therefore they are also incapable of 'suffering', often used
>as a term in textile conservation, but that is another issue though
>probably connected to this one.

Indeed, the use of "life" for artefacts or materials in the field of
cultural heritage might be confusing and seems inappropriate. This
kind of terminology is inherited from the field of science,
technology and industry where it is very often used, ie: "shelf
life" of a product (From Wikipedia: the "shelf life" is that length
of time that food <URL:http://en.wikipedia.org/wiki/Food>, drink,
medicine <URL:http://en.wikipedia.org/wiki/Medicine> and other
perishable <URL:http://en.wikipedia.org/wiki/Decomposition> items
are given before they are considered unsuitable for sale or
consumption <URL:http://en.wikipedia.org/wiki/Eating>, or "life
time" and "half life" (for the decay of radioactive atoms) and so
on.

In the same manner the term "life expectancy" has been applied to
cultural heritage. In the field of archival collections "the
glossary of terms pertaining to stability" (/ANSI/NAPM IT9-13-1996/)
defines life expectancy as "a length of time for which information
can be retrieved without significant loss when properly stored under
extended term storage conditions". A life expectancy of 100 years
(noted LE = 100) means that for 100 years the material will provide
its initial functions properly.

It is true that we could use other words, but it think that the
problem for cultural artifact is not really in the term itself
rather than in determining the "end of life": the limit of
sustainability/durability/usability.

For objects that have a utilitarian function the concept of life
expectancy is straightforward: it corresponds to the length of time
after which the object does not properly ensure anymore the
functions it was conceived for. Do not we commonly say about a light
bulb, a battery, or a car that they are "dead"? Same for a digital
artefact, it can be easy to determine the life expectancy: when
access to the data is no longer possible.

For a museum object (an engraving, a photograph, a painting) change
is a continuous process and if we want to consider life
expectancy/durability/permanence, we have to figure out with some
value ("a dead line"?), thresholds that represent for us an
unacceptable or a just noticeable change. The problem is to select a
relevant criteria/property and to agree to a limit. For color
photography life expectancy could be the time to reach 30% density
loss of a dye, for an acetate film it could be the time to reach 0.5
of free acidity, etc.

Nevertheless, contrary to what might suggest the word, once the life
expectancy reached, does not mean that the object is
"dead"--completely destroyed--but simply it has reached the
threshold. The change of the condition of an object over time does
not mean necessarily a loss of value or functionality. Time shapes
artefacts and, with its marks, it creates culturally significant
signs, which are sources of values. The emotional, historical, or
aesthetical significance attached to cultural artefacts, just to
name some of the values they embodied, are neatly distinct from the
scope of the rational considerations applied to objects of
consumption. That is the reason why defining life
expectancy/usability/durability/permanence for cultural heritage
objects that are pertaining to both natural science and social
science is not an easy task.

Bertrand Lavedrine
Centre de recherche sur la conservation des collections (CRCC)
Paris, France


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                  Conservation DistList Instance 22:64
                   Distributed: Tuesday, May 5, 2009
                       Message Id: cdl-22-64-007
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