Damage function for historic paper. Part II: Wear and tear

Abstract

Background: As a result of use of library and archival documents, defined as reading with handling in the context of general access, mechanical degradation (wear and tear) accumulates. In contrast to chemical degradation of paper, the accumulation of wear and tear is less well studied. Previous work explored the threshold of mechanical degradation at which a paper document is no longer considered to be fit for the purpose of use by a reader, while in this paper we explore the rate of accumulation of such damage in the context of object handling. Results: The degree of polymerisation (DP) of historic paper of European origin from mid-19th–mid-20th Century was shown to affect the rate of accumulation of wear and tear. While at DP > 800, this accumulation no longer depends on the number of handlings (the process is random), a wear-out function could be developed for documents with DP between 300 and 800. For objects with DP < 300, one large missing piece (i.e. such that contains text) developed on average with each instance of handling, which is why we propose this DP value as a threshold value for safe handling. Conclusions: The developed model of accumulation of large missing pieces per number of handlings of a document depending on DP, enables us to calculate the time required for an object to become unfit for use by readers in the context of general access. In the context of the average frequency of document use at The UK National Archives (Kew), this period is 60 years for the category of papers with DP 300, and 450 years for papers with DP 500. At higher DP values, this period of time increases beyond the long-term planning horizon of 500 years, leading to the conclusion that for such papers, accumulation of wear and tear is not a significant collection management concern

Damage function for historic paper. Part III: Isochrones and demography of collections

“…In Part II [2] we defined that the risk of this occurring during an instance of reading in the context of general access is on average very high (even 100 %) for objects with DP <300. We could thus define this value of DP as the threshold value at which objects are no longer suitable for general access.…”

“…We have shown [2] that this is of concern particularly for objects with degree of polymerisation (DP) of cellulose in paper between 300 and 800, while for objects with DP >800, wear and tear accumulates randomly. Objects with DP <300 are likely to develop significant wear and tear (a detached piece of paper with text) in a single instance of handling (reading).…”

“…In our previous contributions in this series, we looked at what makes historic paper unfit for use in the context of general access in libraries and archives [1] and how mechanical degradation accumulates during handling of paper [2]. We have shown that readers and visitors are mostly concerned with loss of pieces of objects, especially if text is also missing.…”

“…Thus, for objects with DP >500, such pieces in average develop over time intervals that are longer than the typical long-term planning horizon of 500 years [3], even for acidic papers. For objects with DP >800, the process becomes random [2].…”

“…without any text loss). In the context of average frequency of object use at The National Archives (Kew), large missing pieces of objects (such that contain text) may develop in ~55 years for paper with DP 300, ~160 years if its DP is 400 and ~450 years if it is 500 [2]. Thus, for objects with DP >500, such pieces in average develop over time intervals that are longer than the typical long-term planning horizon of 500 years [3], even for acidic papers.…”