Reviewed by Ellen McCrady
This study was commissioned by the Library Binding Institute, funded in part by the Andrew W. Mellon Foundation, and administered by the University of Minnesota. It pulls together what is known about the performance of copolymer and homopolymer polyvinyl acetate (PVA) adhesives for double fan adhesive binding of library books. The current LBI Standard calls for the use of copolymer PVAs, which are naturally flexible, but most library binders have been (sometimes unwittingly) using homopolymers, which are made flexible by the addition of plasticizers. The homopolymers may not retain their flexibility if the plasticizer migrates to the surface, as it does under certain conditions; but they were shown by a 1989 LBI study to be stronger, according to the page pull test, and they have been used with apparent success for over 50 years. Since there is no accepted accelerated aging method for predicting the service life of PVA adhesives, the authors say it is hard to tell which is really better, but the consensus of the experts they interviewed was that copolymer PVAs should be used for scholarly volumes printed on paper that will probably last 300 years. Another question calling for an answer was whether the specifications in the LBI Standard could be written on the basis of performance, rather than by naming a specific type of adhesive.
Laboratory and field research on these questions are needed, but before proposing any major research projects, as much relevant information as possible was gathered. Experts were interviewed by phone, using a questionnaire; an informal history of the use of PVAs for adhesive binding was compiled from various sources, including a literature search; discussion was opened with experts on the development of performance-based specifications for the Standard; and several widely-used PVAs were analyzed on a double-blind basis.
The history of PVAs in binding is not well documented: the literature search through two databases turned up just two references. More printed literature was found in trade publications, correspondence files, and conservation literature. It was not possible to travel to Germany to look at the earliest books bound with PVA, so the authors interviewed people who had seen these earliest books instead. These books were all bound with homopolymers, because copolymers were not developed till later. In this country, the earliest books bound with double-fan binding were reportedly bound in the 1950s, but the authors were unable to locate any one of them.
It is interesting that even the copolymers contained plasticizers. However, the manufacturer of Planatol adhesives said that migration of plasticizer can be controlled by holding the content to 7-15%, and Werner Rebsamen's 1991 adhesives study (also published by the Library Binding Institute) suggests that William J. Barrow's study on PVAs may have found problems with plasticizers because of the low molecular weight of those tested.
The experts consulted felt that the acidity of the dried adhesive film would not be likely to contribute acidity to the paper, but if necessary PVAs could be manufactured with a neutral pH.
At present, almost the only test for adequacy of an adhesive binding is the page pull test. The authors explored performance specifications for openability (based on the flexibility and elasticity of the film), durability (in terms of number of circulations of the book) and longevity (based on the expected life of the paper and long-term demand for the books in each kind of library).
Werner Rebsamen's research study is entitled Long Term Service Life and Performance Characteristics of PVA Cold Emulsion Adhesives Used for the Double Fanning Process in Library Binding.
Timestamp: Sunday, 03-Mar-2013 21:37:53 PST
Retrieved: Tuesday, 23-Oct-2018 09:08:20 GMT