Volume 2, Number 4
Oct 1989

Definitions of Permanence and Durability

Permanence

B.L. Browning, The Nature of Paper - 1960. Permanence prefer to distinguish between the concepts of durability and permanence.... Permanence... refers to the degree to which a paper retains its original qualities during storage.

B.L. Browning, Introduction to the 1964 and 1970 Supplements to the IPC Permanence bibliography. Permanence refers to the retention of properties such as strength and color over extended periods. It is influenced by both internal factors (e.g., chemical composition) and external conditions (the effect of light, atmospheric contaminants, etc.).

W.H. Bureau, Preface to the 1977 Supplement to the IPC Permanence bibliography. Permanence refers to the extent to which a paper will retain its original properties upon storage. The extent to which a paper is permanent is generally measured by ... the loss in brightness or whiteness after aging ... and the percentage of its original strength retained after normal or accelerated aging as indicated by fold and tear tests.

API Dictionary of Paper, - 1980. (1) That property ascribed to a material which, under specified conditions, resists changes in any or all of its properties with the passage of time. (2) The permanence of paper refers to the retention of significant use properties, particularly folding endurance and color, over prolonged periods. The permanence is affected by temperature, humidity, light, and the presence of chemical agents. The probable permanence of paper is estimated by an accelerated oven-aging test or by tests under other specified conditions of temperature, light, and humidity. The evaluation of permanence is based on measurement of folding endurance, resistance to water penetration, color, solubility in aqueous alkaline solutions and viscosity of a solution of the fibers in a cellulose solvent.

ASTM D 3290 - 86, Standard Specification for Bond and Ledger Papers for Permanent Records. Permanence - This basically is a function of the chemical stability of the paper and its ability to maintain initial properties over a long period of time. Permanence must be defined with respect to end use, as one paper might be expected to last 50 years and another to last indefinitely. The three levels of permanence ... may be described as follows:

Maximum Permanence - The document is expected to last several hundred years.
High Permanence - The document is expected to last in excess of 100 years.
Medium Permanence - The document is expected to last at least 50 years, and up to 100 years.

Caulfield & Gunderson, "Paper Testing and Strength Characteristics," TAPPI Paper Preservation Symposium, 1988 Permanence is basically a measure of the chemical stability of paper.

Durability

Browning, 1960. Durability is the property of resisting deterioration by use, that is, the handling to which paper may be subjected, the hazards incident to heavy use of books in libraries, or the ability of sandpaper to hold together until the user finishes his work.

Browning, 1964 & 1970. Durability refers primarily to the ability of paper to fulfill its intended function during intensive usage without reference to long periods of storage.

Bureau, 1977. Durability refers to the extent to which a paper will resist deterioration when subjected to use or handling.

API Dictionary, 1980. Durability. The degree to which a paper retains its original qualities under continual usage.

ASTM, 1986. Durability - The ability of a paper to resist the effects of wear and tear in performance situations. For example, paper currency should be durable, but permanence is not a problem.

Caulfield & Gunderson, 1988. Durability ... is primarily a function of the performance of paper; it is a measure of the stability of its physical and mechanical properties. A paper that is given rough treatment over a short time should be durable, but little concern need be given to permanence.

The Relationship Between Permanence & Durability

Browning, 1960 In a sense, permanence may be defined as the retention of durability, whether the latter be small or great. A paper may be durable but not permanent (that is, durability may be lost rapidly because the paper contains an excessive amount of acids), or it may be permanent but not durable.

Browning, 1964 & 1970. Associated with the concept of permanence is that of durability; the two are interrelated, although they are not synonymous.... A paper may be permanent (in retaining its original characteristics) but nondurable (e.g., because of low initial strength), or durable (in resisting intensive usage over a short period) but nonpermanent (e.g., because of the presence of acids).... The true test of permanence lies in actual use....

Caulfield & Gunderson, 1988. The permanence and durability of paper were first distinguished in 1926 [by Gösta Hall, in Paper Trade Journal 84(14) 185] .... A paper that is meant to last for a century must be compounded for chemical stability. Such chemical stability can be enhanced by storing paper at a low temperature; at a constant, low relative humidity; in the dark; and in an atmosphere free of pollutants. But if the paper is also to be used--read, handled, folded, etc.--its mechanical durability is also important. Obviously permanence and durability are not independent of each other, but rather intimately related. This relationship is so infinite, in fact, that durability or the stability of the strength and mechanical properties of paper has become the most useful indicator of its permanence or chemical stability.

Discussion of the Definitions

Although these definitions appear serviceable enough, there are inherent difficulties and ambiguities in each of the concepts which none of the authors has faced. Probably no one will be able to make airtight definitions and use the terms consistently according to their definitions, of these difficulties; but it might not matter anyhow. It is not worth sweating over definitions and distinctions that will never be put to use enhancing communication or annualizing a problem. Definitions that are artificial, in the sense that they are not true reflections of consistent usage among a group of people, have questionable value in any case.

Since there does not seen to be any good reason to tighten up these definitions, the following comments are made for their recreational value only.

The authors do not make it explicit whether the see permanence or durability as an intrinsic characteristic, like "kraft" or "50 lb.," or as a characteristic subject to change, like "white" or "wet." Will a paper be less permanent, in terms of Bureau's or Browning's (1960) definitions, if it is used instead of stored in the future? What if a paper is made for permanence, and meets all the standards, and 75 years later it falls upon hard times? Poor storage could use up the alkaline reserve; pH could fall into the acid range; light could yellow it; and foxing could weaken and disfigure it. Paper that has been affected by all these influences will not be referred to as permanent paper--but this will not be because of its condition at the time, bad as it may be. People would not describe it as permanent even if it is still white and strong. It would be "old but good paper." This is because the phrase "permanent paper" refers to new or relatively new paper, and expresses our confident expectations of its longevity. Similarly, the phrases "growth stock!' or "a fine piece of seaside real estate" express confident expectations, which everyone knows could be shattered by the next stock market crash or hurricane. Since no one knows the future of any piece of paper, and since we need words with which to talk about the paper we have in front of us, the definition of permanent cannot depend an what will eventually happen to that paper. The decision to call a piece of paper "permanent must be made on the basis of what it is at the moment, especially with regard to characteristics known to be associated with longevity. A paper may be more permanent with respect to one characteristic (e.g., tear) than it is to another (e.g., fold or brightness).

In actuality, most of the characteristics that are related to long life in paper change measurably over time, whether the paper is used or stored, with the result that the paper becomes less "permanent" as time goes by. This makes permanence a changeable attribute, like brightness or moisture content, but people do not use the concept this way, though one day they may. Then we will come across statements in books like, "In 1985, this paper had a permanence rating of 9.5 on a scale of 1 to 10, but by 2001 it had declined to 8.5, which is a faster decline in permanence than expected. If this paper is to achieve its expected lifetime of 600 years, it will be necessary to put it in cold storage."

"Durability" is understood by all the authors but perhaps the API to mean "strength at the time of manufacture." No one seem to be confused about whether paper is still durable if it has deteriorated over time; durability is definitely something that can be lost. If paper cannot stand up to use, it is not durable. This usage of the term has a built-in concept of adequacy. It is as if all paper could be sorted into two piles, durable and nondurable; and then the durable paper could be sorted out on a continuum, from minimally to maximally durable. This is all right. We have a large number of concepts like that: interesting, far away, capable, and so on.

However, the concept of durability should not be defined in terms of continual or heavy use. This unnecessarily limits the usefulness of the term "durability." It is like defining "appetite" as "a strong desire for a great deal of food or drink." It is sufficient to say that durability is "the ability to stand up to wear or usage."

This lets us talk about the durability of a paper that has never seen continual or heavy use, and allows us to use the concept of moderate or even low durability.