Marin Hasan

Changes in physical, mechanical and chemical properties of wood during sterilisation by gamma radiation

Abstract Gamma irradiation, which is an easy, fast and effective method for wood sterilisation, changes molecular structures not only in pest cells, but also in wood cell walls. Radiation-induced depolymerisation causes significant changes in some properties of wood crucial for restoration and for laboratory testing of wood-preservative effectiveness, as demonstrated by experimental data. The influence of gamma radiation on maximum swelling (αMAX), resistance to impact milling (RIM), and the total amount of water-soluble carbohydrates (TSC) was investigated. Cobalt (60Co) was used as a gamma source and Scots pine wood (Pinus sylvestris L.) was irradiated at doses of 30, 90 and 150 kGy. A strong linear correlation was found between TSC and radiation dosage. Leached irradiated specimens showed significantly greater TSC content than non-irradiated controls. RIM decreased significantly and linearly with increasing radiation dosage. After leaching, the linearity between these parameters improved. Gamma radiation had no significant effect on αMAX and the time elapsed after irradiation did not influence αMAX, RIM or TSC.

Changes in Selected Properties of Wood Caused by Gamma Radiation

Gamma radiation – as an easy, fast, and effective sterilisation method – changes molecular structures not only in pest’s living cells, but also in wooden cell walls. Radiation-induced depolymerisation causes significant changes in some properties of wood crucial for restoration and for laboratory testing the resistance of wood and wooden products against wood-destroying organisms. Overview of up to date data on the influence of gamma radiation onto some physical, mechanical and chemical properties and on biological resistance against fungal decay are presented.

The Echo (Jeka) Pavilion in Forest-Park Maksimir Zagreb - Restoration and Health Monitoring

The wooden pavilion Jeka (Echo) was built in 1843 according to the plans of the Austrian Empire garden architect Franz Schücht. Echo pavilion is the only remaining one of ten similar pavilions that were placed in the Forest-park Maksimir during the 19th century. Since 1964 the Echo pavilion has been protected by law and declared as cultural monument of garden architecture together with the whole park Maksimir, in which it is situated. Although the pavilion was restored several times (last time in 1986) it was in very bad condition. The reconstruction and preservation of the complete pavilions wooden construction were done after a careful analysis of its recent state in 2000. Restoration of the “Echo” Pavilion was started because its construction was in poor condition and because the whole pavilion was unsafe. There was a severe decay of the lower parts of the poles, particularly those faced to the North. New poles or only the new parts of the poles were made of glued spruce core surrounded by larch heartwood. Organic solvent Tebuconazole and WOODCAP products were used in wood preservation. The restoration of the Pavilion can be seen as an attempt to extend the life time of a severely damaged cultural monument, or at least in those parts of the monument where the amendments were possible. During reconstruction a monitoring system for wood moisture content at three different positions inside the roof construction was installed. Twice a year the pavilion is being carefully visually inspected and data from data logger downloaded and correctness of the equipment verified.This example of the “Echo” Pavilion is showing that moisture monitoring systems can considerably contribute to prevent cultural heritage from decay. The installed inexpensive and simple monitoring system of early warning proved to be feasible and saved costs in the conservation of wooden cultural heritage. In times of tight budgets and increasing rates of decay moisture monitoring systems will become increasingly important.