Disinfection of Mould-contaminated Archival Material by X-ray Irradiation – New Research Results on the Effect on Moulds and Cellulose
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Cornelius Palmbach
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Sebastian Dobrusskin
Abstract
This research project examines the effects of X-rays on cellulose and some moulds frequently found on paper. The aim was to identify applications for X-ray irradiation that can be used as a disinfection method for archival material. The question was if X-rays are suitable as an alternative to gamma radiation and if they are less harmful. For this purpose, the minimum X-ray dose required to reduce the microbial count to a harmless level was determined. The material-altering effect was examined on samples treated with X-rays and gamma radiation. Spectrophotometric measurements showed that there is no noticeable colour change with either type of radiation. The determination of the molecular weight distribution, in turn, showed that the molar mass of the cellulose is considerably reduced with both treatment methods. Using mechanical tests, however, it could be demonstrated that this has no significant influence on the tensile strength. The examination of the oxidation behaviour also showed no significant difference between the differently treated samples. The studies demonstrated that both methods have an almost identical effect on cellulose. Thus, X-ray treatment is primarily a supplement to the known disinfection methods and is particularly suitable for objects that would not withstand treatment with alcohol.
Zusammenfassung
In diesem Forschungsprojekt wurden die Auswirkungen von Röntgenstrahlen auf Cellulose und einige häufig auf Papier vorkommende Schimmelpilze untersucht. Ziel der Studie war es, Anwendungen für die Röntgenbestrahlung als Desinfektionsmethode für Archivgut zu identifizieren. Dabei sollte geklärt werden, ob Röntgenstrahlen als Alternative zur Gammastrahlung geeignet, bzw. ob sie weniger schädlich sind. Dazu wurde die minimale Röntgendosis ermittelt, die erforderlich ist, um die Keimzahl auf ein unbedenkliches Maß zu reduzieren. An den mit Röntgen- und Gammastrahlen behandelten Proben wurde die materialverändernde Wirkung untersucht. Spektrophotometrische Messungen zeigten, dass bei beiden Strahlungsarten keine nennenswerte Farbveränderung auftritt. Allerdings wird die molare Masse der Cellulose durch beide Behandlungsmethoden deutlich reduziert. Mechanische Tests ergaben jedoch, dass dies keinen signifikanten Einfluss auf die Zugfestigkeit der Papierproben hat. Auch im Oxidationsverhalten gab es keinen signifikanten Unterschied zwischen den verschieden behandelten Proben. Die Untersuchungen zeigen also, dass beide Methoden eine nahezu identische Wirkung auf die Cellulose haben. Die Röntgenbehandlung ist in erster Linie eine Ergänzung zu den bekannten Desinfektionsmethoden und eignet sich besonders für Objekte, die für eine Behandlung mit Alkohol nicht geeignet sind.
Résumé
Ce projet de recherche a étudié l’effet de rayons X durs sur la cellulose et sur les spores de moisissures fréquents sur le papier, l’objectif étant de déterminer le potentiel des rayons X pour désinfecter des fonds d’archives infestés par des moisissures. Il s’agissait principalement d’analyser dans quelle mesure les rayons X constituent une solution de rechange aux rayons gamma, notamment en termes de préservation des matériaux. L’étude a ainsi défini le dosage minimal de rayons X pour réduire le nombre des germes à un niveau inoffensif. L’effet de transformation des matériaux soumis à ce dosage minimal a ensuite été examiné à l’aide d’échantillons de cellulose de coton exposés à des rayons X et gamma. La spectrométrie a permis de constater que les deux types de rayons ne provoquent pas de changements de couleur perceptibles à l’œil nu. La distribution de la masse moléculaire a montré pour sa part que les deux méthodes de traitement réduisent considérablement le poids moyen de la masse des molécules de cellulose. Des essais subséquents ont toutefois permis de prouver que cette réduction n'a pas d’impact sur la résistance à la traction. Par ailleurs, les essais réalisés pour étudier le comportement à l'oxydation permettent de conclure que les propriétés des deux échantillons ne présentent pas de différences significatives. L’effet des deux méthodes sur la cellulose est pratiquement identique. Le traitement aux rayons X est ainsi à prendre au sens d’une méthode de désinfection complémentaire par rapport aux méthodes éprouvées, notamment pour les objets qui ne résisteraient pas à un traitement à l’alcool.
Funding source: Innosuisse - Swiss Innovation Agency
Award Identifier / Grant number: 18652.1 PFES-ES
Acknowledgements
Our sincere thanks go to Dr. Paul Raschle (former head of the microbiological laboratory at EMPA, Zurich) for his expert advice, Dr. Giovanna Di Pietro (HKB) and Marcus Jacob (Historisches Museum Basel) for their preliminary work and the preparation of the project proposal, Synergy Health Däniken AG for the irradiation of the samples and the financial support, docusave AG for the vacuum freeze-drying of the samples and the financial support, Swissatest Testmaterialien AG for conducting the microbiological study, Prof. Dr. Antje Potthast and Dr. Sonja Schiehser (Institute for Chemistry of Renewable Resources at the University of Natural Resources and Life Sciences, Vienna BOKU) for determining the molecular weight distribution and Dr. Agnes Blüher (Swiss National Library in Bern) for providing the Bansa-Hofer folding device.
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Research funding: The research project was co-financed by Innosuisse - Swiss Innovation Agency (No. 18652.1 PFES-ES).
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Research project: Röntgenbestrahlung zur Desinfektion von cellulose-/papierhaltigen Archiv-und Kulturgütern (www.hkb.bfh.ch), 2017–2019, Bern University of Applied Sciences (BFH), Department Bern Academy of the Arts (HKB), Institute Materiality in Art and Culture (IMIKUK), project management: Cornelius Palmbach, responsibility: Sebastian Dobrusskin, team: Dr. Mathieu Jacot-Guillarmod, Olivia Raymann, implementation partners: Synergy Health Däniken AG (www.steris-ast.com), docusave AG (www.docusave.ch).
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Author contributions: Irradiation of the samples was performed at Synergy Health Däniken AG under the guidance of Hans Hartmann. The microbiological study was performed in the laboratory of Swissatest Testmaterialien AG under the guidance of Caroline Amberg. Vacuum freeze-drying was performed at docusave AG under the guidance of Guido Voser with assistance from Barbara Mordasini Voser and Gianclaudio Mordasini. Spectrophotometric measurements and tensile strength tests were performed in the laboratory at HKB by Cornelius Palmbach. Chemiluminescence measurements were performed in the laboratory at HKB by Dr. Andreas Buder. Sebastian Dobrusskin, head of the specialisation Graphics, written materials and photography of the degree programme Conservation and Restoration at HKB, provided continuous expert advice for the project. Dr. Mathieu Jacot-Guillarmod and Olivia Raymann made an important contribution to the success of the project with their research on the physical fundamentals of X-rays and gamma radiation as well as on alternative disinfection methods. Image credits: Figures 1–7 and 10 by Cornelius Palmbach, Figures 8 and 9 by Andreas Buder.
Appendix
List of materials
Whatman® filter paper no. 1 (WHA1001931, Sigma Aldrich): To determine the MD, the longitudinal and transverse edges of a piece of paper were moistened with water using a brush, causing the edges to become wavy. The CD and the MD can then be distinguished based on the pronounced waviness: the edge where the corrugation is less pronounced runs parallel to the MD (Teschner 2017, 906ff).
Rag paper: Cut-off, unprinted margins of the pages of an 18th-century book.
Instrumentation
X-ray radiation unit Rhodotron TT-1000 (IBA SA): Electron beam accelerator with tantalum target (Abs et al. 2004), photon energy: 7 MeV, power: 700 kW, increments: 2.8–2.9 kGy.
Gamma radiation unit (Nordion, Canada): Radiation is provided by bars made of the radioisotope cobalt-60. Photon energy: 1.17 MeV and 1.33 MeV, power: 3.5 MCi, increments: 3.4–3.5 kGy.
Dosimeter Alanine TapeTab (Harwell Dosimeters LTD): Alanine strip dosimeters read out using an electron spin resonance (ESR) spectrometer. The dosimeters were handled according to ISO 9001, ISO 13485, ISO 11137 and 21CFR Part 820 (FDA c GMP).
Spectrophotometer Spectrolino™ (Gretag Macbeth AG), colorimetry: CIE-L*a*b*, illumination: D65 (approximated daylight, colour temperature: 6504 K), observer angle: 10° normal observer, evaluable values: spectrum R (remission in the wavelength range 380–730 nm in 10 nm steps).
SEC-MALLS/RI instrumentation: The Agilent GPC system consisted of a MALLS (Dawn DSP 488 nm, Wyatt Corp.) and refractive index detector (Shodex RI-71) with automatic injection on four serial columns. DMAc/LiCl (0.9%, m/V, filtered through 0.02 µm) was used as the eluant. MWD and related polymer-relevant parameters were calculated by software programs ASTRA 4.73 and Grams, based on a refractive index increment of 0.140 mL/g for cellulose in DMAc/LiCl (0.9%, m/V) at 488 nm. GPC parameters: flow: 1.00 mL/min; columns: four, Agilent PL gel, mixed A-LS, 20 µm, one pre-column, 7.5 × 300 mm; injection volume: 100 µL; run time: 45 min.
Chemiluminescence measuring device CL1.0 V.5 (ACL Instruments AG)
Bansa-Hofer folding device: The device consists of an inclined plane tilted at 20° to the horizontal and a 500 g cylindrical mass. After 30 cm, the strip-shaped sample clamped in a loop protrudes through a slot from below into the rolling path. After releasing the locking mechanism, the mass rolls down from the upper end of the inclined plane across the paper loop. Thereby, the loop is pressed flat with always identical force, providing the sample with a defined fold.
Tensile tester zwickiLine Z2.5/TN1S (Zwick Roell AG): Tests were performed following the DIN 53112 standard (meanwhile replaced by the DIN EN ISO 1924-2 standard). Initial force: 5 N/m, test speed: 20 mm/min.
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Supplementary Material
This article contains supplementary material (https://doi.org/10.1515/res-2022-0016).
© 2023 Walter de Gruyter GmbH, Berlin/Boston
Articles in the same Issue
- Frontmatter
- Original Works
- Disinfection of Mould-contaminated Archival Material by X-ray Irradiation – New Research Results on the Effect on Moulds and Cellulose
- Treatment of a Severely Damaged Paper Manuscript of the Tang Dynasty Unearthed from the Western Regions
- Mineral Clays for Cleaning Tidelines on Paper-Based Artworks
- Technical Note
- Didactic Panel Illustrating Light Exposure Effects
Articles in the same Issue
- Frontmatter
- Original Works
- Disinfection of Mould-contaminated Archival Material by X-ray Irradiation – New Research Results on the Effect on Moulds and Cellulose
- Treatment of a Severely Damaged Paper Manuscript of the Tang Dynasty Unearthed from the Western Regions
- Mineral Clays for Cleaning Tidelines on Paper-Based Artworks
- Technical Note
- Didactic Panel Illustrating Light Exposure Effects
