J. PERKOWSKI
Institute of Applied Radiation Chemistry, Lodz
W. GŁUSZEWSKI
Institute of Nuclear Chemistry and Technology, Warsaw
Email: w.gluszewski@ichtj.waw.pl Poland
18.1. INTRODUCTION
Historical objects are exposed to a number of adverse factors: chemical (corrosion and chemical reactions of various types), physical (atmospheric agents, e.g. changes in humidity, temperature), mechanical (vibration, shock, impact, etc.) and, perhaps the most dangerous, biological agents. Biological degradation of historical objects is done by both the smallest and simplest organisms (bacteria, fungi, moulds) and more complex organisms (mostly insects). Destruction can also be caused by birds and mammals (particularly rodents), but these phenomena are rather marginal and much easier to control.
The physical factors which can be used to combat pests in historical objects include temperature, ultrasound, ultraviolet radiation and ionizing radiation (X ray, gamma, EB). Radiation techniques are ideal for situations when there is a need to disinfect a very large number of objects. Ionizing radiation may be the only method of conservation that ensures control of bacteria and mould contamination in a short time. Other advantages of gamma radiation are its high penetration and the fact that its effectiveness does not depend on the shape and structure of the material, which allows disinfection of objects with large dimensions and complex shapes.
Described below is an example of radiation disinfection of a large collection of artefacts carried out by the Institute of Applied Radiation Chemistry (IARC) at the Faculty of Chemistry of the Technical University of Lodz, Poland, for the State Museum at Majdanek. The project involved the disinfection of 60 000 shoes
that belonged to camp prisoners. The museum was founded in November 1944 on the grounds of a former concentration camp. It is an institution managed by the Ministry of Culture and National Heritage in Poland. Its main duties include keeping the area of the former camp at Majdanek with its buildings and appliances in proper condition, as well as substantiating the history of the camp.
18.2. PRISONERS’ SHOES IN THE COLLECTION OF THE STATE MUSEUM AT MAJDANEK
In the early post-war years, the shoes found in the camp were sorted into several categories depending on their origin, material, finish and size. The categories included civilian shoes for adults and children, clogs made in the camp, wooden soles for use in the camp shoemaker’s workshop, and shoes made of straw. Most shoes were adults’ and children’s shoes that belonged to Majdanek prisoners. According to estimates, the collections of the museum include approximately 280 000 civilians’ shoes: approximately 245 000 for adults and approximately 35 000 for children. These are made of leather, cloth, rubber and wood. The exact time of their origin is unknown, but it can be assumed that most of them were made in the 1930s. Different styles and models are represented, among them both high quality shoes (the work of shoemakers throughout Europe, as evidenced by preserved labels) as well as simple shoes made by artisans who supplied peasants in Poland, Ukraine and Belarus. The condition of the shoes varies. The vast majority have heavily worn soles and heels as a result of intensive use by their owners (especially the men’s shoes, with numerous traces of repeated repair and patching) or deliberate disruption in search of valuables and notes, often hidden by the deportees in their shoes (see Fig. 18.1).
In 1998, the museum received funding from the Foundation for Polish-German Cooperation for renovations on barracks 53 and 54. Thereafter, efforts were initiated to obtain funds for the preservation of footwear, temporarily kept in 2 571 jute bags in one of the barracks (Fig. 18.2). Assistance was sought from the Council for the Protection of Struggle and Martyrdom Sites, the Society for the Protection of Majdanek and the Ministry of Culture and National Heritage. In 2001, the museum received a grant from the Ministry of Culture and announced a tender for partial preservation of 150 000 units of prisoner footwear.
The IARC, which had proposed the implementation of non-invasive radiation disinfection and mechanical cleaning, was selected to carry out the work [18.1].
Owing to financial constraints, it decided to reduce the number of shoes to be treated to 60 000.
18.3. RADIATION DISINFECTION OF 60 000 SHOES
The 60 000 shoes were packed into 500 bags (the size of the bags was 60 cm × 100 cm × 35 cm) and transported to the IARC gamma irradiation facility.
Based on a preliminary microbiological analysis, an absorbed dose of 20 kGy was chosen as the minimum dose required for achieving the desired degree of removal of microorganisms. The shoes were irradiated in the bags, which were laid centred in the irradiation chamber in four layers of 14 pieces. In order to
FIG. 18.2. The 60 000 treated shoes on display at the barracks.
improve the uniformity in the absorbed dose, the bags were moved and rotated in the middle of the exposure period. Under the irradiation conditions, the absorbed dose variation observed was about 7.5%. The microbiological analysis looked at the total number of bacteria and fungi on the surface of the shoe before and after irradiation. A reduction of bacteria in the range of 95 to 99.9% was obtained, while the reduction in fungi was between 80 and 97%. Shoes, like any disinfected object, should be protected from secondary infection. One way to ensure this is to store and display them under the right conditions.
18.4. METHOD OF CONTROLLING THE RADIATION DOSE
The prime technical concern with irradiation of museum artefacts is to ensure the highest homogeneity of absorbed dose to ensure that the process results in the desired microbiological control. This is very challenging as these objects may be made of various types of material and have varying sizes, shapes and other special features that require individual treatment in the radiation disinfection process. The method of treatment may also include optimizing the irradiation geometry as well as the geometry of the radioactive sources.
The existing IARC irradiation chamber with dimensions of 414 cm × 350 cm × 220 cm was equipped with 20 sources located in a circle with a total activity of about 0.74 × 1015 Bq. It enabled the irradiation of large objects, but with significant differences in the dose rate in different parts of the object. A computer simulation program was used for calculating the distribution of dose rate. The program allowed the user to make quick calculations of dose distribution depending on the location of the object in the chamber and the thickness and type of radiation absorbing material. The results obtained made it possible to develop an optimal plan for conducting the irradiation process.
REFERENCE TO CHAPTER 18
[18.1] OLESIUK, D., Obuwie więźniarskie w zbiorach Państwowego Muzeum na Majdanku, Zeszyty Majdanka 24 (2008) 235–262.