It has been shown that tetraethoxysilane-derived precursors are suitable solutions for impregnating pine sapwood to improve its dimensional stability. Tailored sol–gel syntheses result in precursors with nano-scaled silica species which are able to penetrate into the cell walls of wood. The physical fixation of those species inside the cell walls was verified by ESEM/EDX investigations. There is evidence that the silica species are chemically bonded to wood components. Nonreacted alkoxy groups can exist in the wood composites after impregnation. The amount of these organic residues depends on the composition of the precursors, especially their condensation degree and reactivity. Treatments for finishing the composites after the impregnation step to get clean products and stable properties are discussed in this context. An explanation of the complex relationship between solids content in the impregnation solutions and percentage weight gain and bulking of the composites is given. It can be demonstrated that high WPG values (>20 %) are pre-conditions for an effective protection of the resulting composites but they only guarantee efficient improvements if connected with the incorporation of the inorganic component inside the cell walls. Therefore, the sol–gel syntheses have to be carried out in such a manner that very small (<2 nm) as well as reactive species are sufficiently available. This demands syntheses using sub-stoichiometric water contents (H2O/TEOS <4, better <2).
Die evangelische Friedenskirche in Schweidnitz (Polen) ist ein besonderes Zeugnis des deutsch-polnischen und damit europäischen Kulturerbes. Deshalb wurde sie auch 2001 einstimmig vom UNESCO-Komitee in die Liste des Kultur- und Naturerbes der Welt aufgenommen. Sie stellt ein einmaliges Denkmal des hoch entwickelten schlesischen Fachwerk- und Holzbaues aus dem 17. Jahrhundert dar. Im Rahmen einer interdisziplinären Zusammenarbeit zwischen Fachleuten aus Deutschland und Polen erfolgte die fachgerechte Restaurierung von 39 Fensterverglasungen und Rahmen mit dem Ziel, eine Abdichtung des Kirchenraumes gegen eine zeitweilig zu feuchte und mit Schadstoffen angereicherte Außenluft zu erreichen. Die Bundesanstalt für Materialforschung und -prüfung in Berlin führte Untersuchungen zu den klimatischen Bedingungen im Kirchentraum durch, um für die Kunstschätze nachhaltig verträgliche Bedingungen zu sichern. In der Friedenkirche war, wie auch in vielen anderen Bauwerken, in den 70-er und 80-er Jahren des 20. Jh. das Holzschutzmittel Xylamon verwendet worden. Neben der Gefahr für die sensiblen Materialien der Kunstwerke ist durch Holzschutzmittel auch ein Einfluss auf die Gesundheit von im Kirchenraum befindlichen Personen nicht auszuschließen. Mit Hilfe unterschiedlicher Untersuchungsmethoden konnten Emissionen aus Holzschutzmitteln und ihre Verbreitung im Kircheninneren nachgewiesen werden.
A number of environmental monitoring projects were performed on historic stained-glass Windows in Germany from 1994 to 2012. The quality of the protective glazing was assessed by recording environmental Parameters in the interspace between the original and the protective glazing and on the inside of the original window. Tor this purpose, temperature, humidity and air velocity were measured. Particles were sampled with different methods and analysed by scanning electron microscopy combined with energy dispersive X-ray spectroscopy to determine their chemical composition. The effect of particles on model glass samples was investigated in climate chambers under accelerated weathering conditions. The results from in situ measurements and laboratory tests were combined to evaluate the potential effect of particulate matter on historic stained-glass Windows.
The antileaching efficacy of sol-gel-derived TiO2- and SiO2-based precursors has been evaluated through laboratory leaching trials with pine sapwood in two different ways. In a one-step process, wood was vacuum impregnated by the precursor solutions containing CuCl2. The copper (Cu) emission rates of the sol-gel-based impregnated woods were up to 70% lower than that of wood treated with pure CuCl2 solution at the same level of concentration. More improvement (80%) could be achieved in a two-step process, in which sol-gel precursors were introduced into an already CuCl2-treated wood. The refinement was attributed to several effects. In the one-step approach, Cu was embedded in the TiO2/SiO2 gels formed in the wood texture. During a two-step impregnation, gel layers that were formed in the wooden interior acted as an effective diffusion barrier. The sol-gel impregnations made wood more hydrophobic; therefore, the low amount of water that penetrated the cell wall was less efficient to leach out Cu.
A comparative study tested the performance of modern anti-corrosion Systems against that of traditional red lead Systems.
One aim of the research project was to find alternatives for the use of a red lead priming coat, the Standard anti-corrosive primer for iron and Steel in the past but a material which endangers health as well as environment. The investigation aimed to determine whether anti-corrosion Systems developed for industrial use were suitable for the Conservation of historic iron and cast iron objects.
Besides coatings containing red lead, several surface tolerant coatings with different anti-corrosion pigments were examined.
The modern anti-corrosion Systems examined were suitable for surfaces where Optimum surface preparation is not practical.
They were applied to both historical samples and to newly prepared model samples.
After uniform pre-corrosion, the model samples were coated and underwent two different ageing procedures: accelerated ageing in a climate chamber and outdoor weathering on a test site with moderate city climate. The specimens were exposed for more than two and a half years. Evaluation of the artificially aged samples was carried out under the aspect coating degradation, tensile strength test, cross-hatch test and Fourier-transform infrared microscope.
The results of the research with optical evaluation and test procedures will be presented. The two ageing methods will be discussed, with different results from the naturally and artificially aged samples. The results Show a similar eligibility of modern anti-corrosion Systems as compared with red lead Systems for the use in Conservation.