Treatment principleBattelle
Development
By order of Die Deutsche Bibliothek (German National Library, Frankfurt/Leipzig), and supported by a grant of dm 17.5 million from the German Bundesministerium für Forschung und Technologie, Battelle Ingenieurtechnik GmbH has since 1987 been investigating different deacidification methods to develop the most suitable system. The first approach, put in operation in a pilot plant in Frankfurt, was a process based on the liquid-phase Wei T'o system, using magnesium methyl carbonate (mmc) as deacidification agent and freon solvents. Though the treatment procedure is similar to that of the Wei T'o system discussed below, several improvements had been realized by the end of 1990, including optimized recycling, fast and homogeneous drying by means of microwaves, and automatization of the process control (Schwerdt 1989).A change in the solvent and, as a consequence, in the effective deacidification agent, was necessitated by the stricter environmental regulations for the ozone-depleting freon compounds, as laid down in the 1987 Montreal Protocol (Gesetz 1988, Montrealer 1988). The solvent was replaced by hexadimethyl disiloxane (Wittekind 1994a), a colorless organic silicon compound which according to Battelle is not harmful to health and environment. However, hexadimethyl disiloxane is highly flammable. mmc has been replaced by magnesium titanium ethoxide (mete) as effective deacidification agent. mete is a combination of magnesium ethoxide and titanium ethoxide, and according to Battelle capable of both deacidifying and strengthening of paper. Finally a compound was added to diminish the surface tension of the deacidification solution, in order to improve the impregnation in paper. The Battelle pilot plant, constructed in Frankfurt, was moved to the Deutsche Bücherei (Leipzig) and put into operation in 1994.
By using microwave heating equipment, combined with an ingenious control of the radiation process, the drying step could be shortened to approximately 2 hours (Behrens 1993). However, in the course of time, test results showed that the microwave procedure posed many technical and practical problems. For instance, local heat damage of paper caused by metal staples and wire stitches presented a serious problem as these stitches are not uncommon, and especially frequent in German books from the 19th and early 20th century. Consequently, Battelle Ingenieurtechnik decided to replace the microwave equipment by a conventional drying technique, using reduced pressure and heat. This modified installation is currently being constructed in Eschborn, the new location of Battelle since 1993.
| Type of process | Battelle/liquid-phase |
| Effective agent | Magnesium titanium ethoxide (METE): Mg(OC2H5)2 and Ti(OC2H5)4 |
| Solvent | Hexadimethyl disiloxane (HMDO;(CH3)3SiOSi(CH3)3) |
| Procedure | The current deacidification procedure consists of 4 steps: (i) Predrying: the paper to be treated is dried for 2 days in vacuum at 60°C, in order to decrease the water content from approximately 6% to 0.5%; the materials are placed in special boxes. (ii) Impregnation: the deacidification solution penetrates easily in the paper, and the impregnation and deacidification are completed in only a few minutes; subsequently the deacidification solution is drained. (iii) Afterdrying: the remaining deacidification solution in the paper is removed as in the predrying step, by means of vacuum and heat. (iv) Reconditioning: after completion of the drying, the documents are reconditioned for 3 weeks in order to regain normal water content in the paper; the storage room is well ventilated in order to diminish the odor of the treated materials. Formerly both drying steps were performed by means of microwaves. |
| Initial reactions | Magnesium ethoxide and titanium ethoxide hydrolyse easily in the presence of water in the paper. In first instance a metal hydroxide is formed: Mg(OC2H5)2 + 2 H2O -> Mg(OH)2 + 2 C2H5OH Ti(OC2H5)4 + 4 H2O -> Ti(OH)4 + 4 C2H5OH The forming of ethanol (C2H5OH) is probably the cause of the typical (sweet) odor of the treated paper. Under influence of the environmental air, a second reaction step will form magnesium carbonate (MgCO3) and titanium dioxide (TiO2). |
| Deacidification | The magnesium carbonate and the residual metal hydroxides neutralize the acids present in the paper. |
| Alkaline reserve | The excess of magnesium carbonate in the paper forms the alkaline reserve, protecting the paper against future acidification. |
Research results
The first thorough and independent scientific studies of the Battelle process have been performed in the Netherlands. In 1994 the cnc, the National Preservation Office of the Netherlands, reported the results of a pilot study on the effects of the Battelle deacidification method, which indicated a number of advantages and disadvantages (Pauk 1994). The cnc decided to do a more elaborate study on the Battelle method, which was carried out by tno Center for Paper & Board Research in Delft and the Koninklijke Bibliotheek in The Hague (Deventer 1995, Pauk 1995, Havermans 1996).
The primary aim of the investigations was to obtain a thorough insight into the positive and negative effects of the Battelle deacidification method on books and archival materials. Important aspects were the directly observable effects of the treatment, the homogeneity of the deacidification, and the effect on the permanence of the paper. For permanence, both chemical and physico-mechanical paper characteristics were examined; not only the effects of accelerated (thermal) ageing were investigated, but also the protection offered by the deacidification treatment against the air pollutants sulfur dioxide and nitrogen dioxide.
In general, the Battelle deacidification appeared to result in a positive contribution to the permanence of the paper, both in books and in archival materials. In 84% of the books, and 2 out of 3 archival materials, paper degradation was convincingly inhibited in the long term, and there were clear indications that the Battelle treatment protects against the influence of acid air pollutants.
Despite these positive results it was concluded from the research results that the Battelle process suffers from a number of shortcomings which could obstruct a large-scale application. In the first place a large part of the testmaterial (40% of the books and 2 out of 3 archival materials) showed a significant immediate decrease in paper strength as a direct result of the deacidification treatment. Moreover, the ageing tests showed that also in the long term a considerable part of the tested books (16%) and archival materials (1 out of 3) do not benefit from the Battelle treatment. Secondly, despite the introduced improvements in the treatment procedure, there were still undesired side effects in the deacidified materials, such as discolorations, white deposit, Newton rings, bleeding of inks and dyes, odor and the different `feel' of the paper. Finally there was no homogeneous distribution of the deacidification agent in books and compact stacks of paper.
There were indications that certain properties of paper, such as porosity and nature of sizing may have an influence upon the effect (positive or negative/no effect) of the Battelle treatment on paper permanence. Further investigation of these paper characteristics is recommended in the research report, also in order to come to a definition of inevitable preselection steps for the Battelle system.
The results of the cnc investigations, as summarized here, are in contradiction with the claims put forward by Battelle on the basis of their own test results (Wittekind 1994a, 1994b). Both the alleged general strengthening, as a direct result of the treatment, and the absence of undesirable side effects appear to be disproved. However, the materials tested in the cnc investigation were treated by Battelle in the summer of 1994, and Battelle has stressed that since then additional improvements have been introduced in the treatment procedure, especially in the drying steps, resulting in the further reduction of side effects and improved homogeneity of the deacidification (Wenzel, pers. comm. 1996).
Last year the modified process was tested by several German libraries and archives. Of the institutions involved, the following responded to a request for information: the Landesarchiv in Berlin (Dettmer, pers. comm. 1996), the Staatsbibliothek zu Berlin (Baron, pers. comm. 1996), the Bibliothek für Bildungsgeschichtliche Forschung in Berlin (Bierwagen, pers. comm. 1996), the Deutsches Museum in München (Berninger, pers. comm. 1996), the Bayerische Staatsbibliothek in München (Trapp, pers. comm. 1996), the Bundesarbeitsgericht in Kassel (Welle, pers. comm. 1996), the Max-Planck-Institut für Europäische Rechtsgeschichte in Frankfurt (Deter, pers. comm. 1996), the Universitätsbibliothek in Mannheim (Leichert, pers. comm. 1996), the Hessisches Staatsarchiv in Darmstadt (Wolf, pers. comm. 1996), the Hessisches Landes- und Hochschulbibliothek in Darmstadt (Staub, pers. comm. 1996) and the Landesbibliothek in Coburg (Erdmann, pers. comm. 1996). Although the investigations are not yet fully completed, the first results of the performed test runs are generally considered encouraging.
Over the last few years the Battelle system has also been tested in Switzerland by the Landesbibliothek (National Library) and the Bundesarchiv (Federal Archives), in cooperation with the Wimmis Pulverfabrik. The results of the tests with regard to the effectiveness of the deacidification and to the occurrence of side effects were promising and met the minimal requirements established in July 1995 (Herren 1994, Herren 1995, Herion, pers. comm. 1996).
Application
The first Battelle installation, put into operation in a library setting, was installed in 1994 in the Deutsche Bücherei (Leipzig). It has been estimated that the number of books to be deacidified in Die Deutsche Bibliothek (German National Library, Frankfurt/Leipzig) is around to 12 million (Lehmann 1992). Although the Battelle installation is intended to deacidify 400,000 books per year, the actual treatment has until January 1996 been limited to approximately 60,000 books, and the system is not yet operating on a continuous basis. Together with technicians from Battelle, work is still in progress to adjust and optimize the treatment procedure. A special problem is the predrying of the books, for which originally microwave equipment has been installed, creating the technical and practical difficulties already mentioned above (Wächter, pers. comm. 1996).
A Battelle installation at present under construction in Eschborn has been set up as a service center for German libraries and archives and will initially have a capacity of 120,000 books per year. The treatment costs will depend on the size and weight of the books, and on the magnitude of the contract with Battelle. For octavo-format books with an average weight of 0.5 kg, costs per book are estimated at dm 15–20, including transport and insurance. The materials to be treated should be packed by the customers themselves in special boxes of metal wire. The sealed boxes are transported to Eschborn for treatment, during which the books remain in the boxes. After the treatment the boxes will be returned. The Battelle center in Eschborn is planning to extend its services to include freeze-drying of water-damaged materials and treatment of biological damage by insects and fungi. Plans to found additional Battelle service centers in Germany are still in a preliminary stage (Behrens, pers. comm. 1996).
Worth mentioning is the initiative of the Landesbibliothek (National Library) and the Bundesarchiv (Federal Archives) in Switzerland to establish a Battelle installation for the deacidification of books and archival materials. On the basis of a survey performed on mass deacidification systems and of comparative testing of the dez and fmc processes, it was concluded that the Battelle system offers the best prospects. After a one-year detailed engineering phase, starting in May 1996, plans and cost estimates for the Battelle plant will be submitted to the Swiss Parliament in 1997. Construction is planned for the beginning of 1998, and the plant should be operational at the end of that year (Herion, pers. comm. 1996).