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- Klimamessungen (2)
- Mittelalterliches Glas (2)
- Protective glazing (2)
- Stained glass (2)
- Umweltsimulation (2)
- 3D inspection (1)
- Adhesives (1)
- Analyse (1)
- Analytik (1)
- Archäometie (1)
Organisationseinheit der BAM
To improve the adhesives used for restoring stained glass windows, various adhesives were tested and modified. Stained glass windows often show gaps that are too wide to be glued with conventional adhesives, and complementing the gap with spare glass is very time-consuming.
To solve this problem, a filler with improved adhesive strength was developed to bridge wider gaps and cracks. The new filler combines glass adhesives with specially treated glass powder.
Three different glass adhesives were selected and mixed with the specially treated glass powder. The adhesive – glass powder mixture developed was then subjected to accelerated aging and analysed with Fourier transform infrared analysis, scanning electron microscopy, colourimetry, and bending and tensile tests. The results were excellent and the mixture was subsequently used to restore glass windows from four 19th-century churches and chapels. The restoration process was described in conjunction with the advantages of using this approach.
This new adhesive – glass powder mixture provides an adhesive process that can be adapted to the special needs of any object being restored and thus provides a ready answer to the specific damage of each object.
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.
Several restoration projects of stained-glass windows have been performed in Lower Silesia (Poland) since 2010. The aim of the projects was to protect stained-glass windows against environmental impact of industial pollutants and acid rain by installing a protective glazing. The usefulness of protective glazing has been proved by climate measurements and determination of environmental impact before and after installation.
Corrosion of historic timber
(2014)
With the implementation of glass casting in France in the second half of the 17th century, larger mirrors could be produced. So-called tin-mercury mirrors were made by coating glass with tin amalgam. Today, many historical mirrors are partly damaged, the image quality is compromised, and the material integrity of the mirror is threatened. The transformation from tin into an oxide starts at the surface of the amalgam and proceeds down to the glass surface. The mercury dissolves as a liquid or gaseous phase. The amalgam layer is destroyed, so that conservation is necessary. Conservators must follow strict safety precautions while handling amalgam mirrors because of possible mercury emissions and corrosion of the amalgam, during which elemental mercury accumulates near the mirror frame in droplets and is emitted into the air.
In a research project, the quantity of the mercury emissions from historical mirrors was examined and a technique to decrease these emissions was developed.
Scientific investigation for a medieval stained glass conservation project at Lincoln Cathedral
(2015)
Between 2013 and 2017 four medieval lancet windows located in the south-west transept of Lincoln Cathedral are being restored and conserved at the Cathedral Glazing Department. The great majority of the glass dates from the 13th century with some pieces dating from the 13th century (Morgan 1983, pp. 21-24). in order for the conservation and cleaning of the medieval glass to take place, scientific investigations were carried out at the Federal Institute for Materials Research and Testing (BAM), Berlin. The pre-conservation analysis examined the glass before any cleaning method had taken place to establish the state of the glass and its surface. A later post-cleaning analysis would provide information regarding the effectiveness of the different cleaning methods.
Nach 1850 wurde zur weiteren Herabsetzung der Einbrenntemperatur von Glasmalfarben Borax (Na2B4O7 · 10 H2O) zugesetzt. Das Verhältnis war nun 1 Teil SiO2, 3 Teile PbO und 0,5 Teile Borax. Der analytische Nachweis von Bor in eingebrannten Malschichten war bisher jedoch nicht möglich.Daher wurden in Laborversuchen Glasmalfarben mit unterschiedlichem Gehalt an Borax auf Modellgläser aufgetragen, eingebrannt und anschließend unter simulierten Umweltbedingungen zeitraffend im Klimaschrank bewittert.
Mit Hilfe von elektronenmikroskopischen Untersuchungen können Malschichten charakterisiert werden und somit Hinweise auf mögliche Schadensursachen liefern. Erste Versuche zum Nachweis von Bor erfolgten mit Hilfe von LIBS-Messungen (Laser Induced Breakdown Spectroscopy) an im Labor hergestellten Glasmalfarben mit unterschiedlichem Boraxgehalt.
The initial focus of this research was on the development of a general workflow for the documentation and monitoring of historical stained glass windows using structured light scanning. Therefore windows from different churches, time periods and with different corrosion and damage phenomena were scanned before and after conservation measures. To evaluate the execution of the restoration measures the data was compared using 3D inspection software to examine the differences in geometry between the two scans. Various problems had to be solved, for example, how to deal with heavily reflective surfaces and the extreme contrast between light and dark surfaces, as seen in the borders between ‘Schwarzlot’ painting and plain glass. The application of materials for matting the surfaces, such as Cyclododecane spray, was impossible due to the high accuracy of the surface measurement required for 3D inspection. Regarding the contrast differences of the surfaces, the creation of exposure fusions and the use of polarization filters to reduce reflections were tested. In addition to the general problems encountered when recording translucent surfaces, the historical glasses caused additional problems in calculating surface comparisons. For example, the windows have to be moved and turned around several times, both during the conservation process and while scanning, causing deformations of the geometry due to the flexible lead rods allowing a certain degree of movement.
Glas ist ein sehr verbreiteter Werkstoff und eines der ältesten Produkte neben Keramik, Eisen und Bronze, die der Mensch schon frühzeitig herzustellen in der Lage war. Es dauerte jedoch Jahrrausende bis zur ersten wissenschaftliche Beschreibung der Glasstruktur. Sie erfolgte erstmals 1903 von TAMMANN als eine stark unterkühlte Flüssigkeit. VOGEL (1992) gibt einen Überblick über die klassischen Glasstrukturtheorien. Ganz allgernein kann Glas als ein anorganisches Schmelzprodukt definiert werden, das abgekühlt und erstarrt ist, ohne zu kristallisieren, weshalb Glas auch durchsichtig ist. Es kann aus einfachen und nahezu überall und unbegrenzt vorhandenen Rohstoffen hergestellt werden. Die Hauptbestandteile sind Sand, Soda, Pottasche und Kalk. Wesentliche Eigenschaften des Glases sind seine gute Verarbeitbarkeit mir verschiedenartigen Techniken wie Gießen, Blasen, Ziehen und die Möglichkeit, durch die Zugabe von unterschiedlichen Oxiden auch farbige Gläser herzustellen.