Issues in Contemporary Oil Paint by unknow

Author:unknow
Language: eng
Format: epub, pdf
Publisher: Springer International Publishing, Cham

Experimental

Sulfur tetrafluoride SF4 (ABCR® Dr. Braunagel GmbH & Co. KG, Art No. AB10417) treatment in gas phase was used derivatise different kinds of oil paint micro-samples as well cross-sections. The micro-samples were rolled on to a CVD diamond window prior to placement into the gas reaction chamber. Stratigraphic samples were embedded in epoxy resin Araldite 2020 (2 component XW396/397) and sections were prepared using dry polishing cloths of the type Micro-mesh®. The derivatisation treatment using the active gas SF4 was performed in an all-teflon® chamber (volume 10 cm3) (Carlsson et al. 1988; Mallégol et al. 2000c). All samples were exposed to the SF4 gas at room temperature for 24 h. Before and after the reaction, the chamber was flushed with nitrogen N2 and the eliminated gas was adsorbed to active charcoal. FTIR measurements were performed on a Bruker® Hyperion 3000/Tensor 27 infrared spectrometer with a germanium ATR crystal (∅ 250 mm). The pixel resolution is 0.5 μm with the FPA detector made of 64 × 64 detector elements, covering an area of 32 × 32 μm. Micro-samples were analysed in transmission mode at 4 cm−1 spectral resolution and 32 scans. The 2D FTIR-FPA imaging was performed in ATR mode at 8 cm−1 spectral resolution and 64 scans. More details can be found in (Zumbühl et al. 2014). The electrospray ionisation mass spectrometric ESI-MS measurement was performed with a Bruker maXis 4G UHS-TOF (Ultra High Resolution Time of Flight) mass spectrometer at the University Duisburg-Essen (Institute for Organic Chemistry). The samples was extracted in a chloroform / methanol mixture and measured in the positive mode.

To investigate the oxidation gradients in very thick paint layers, accelerated ageing tests were performed. The paint products used were linseed oil paint (Kremer GmbH & Co. KG) containing basic lead white (Kremer 460007) and zinc white (Kremer 463207) without dryer content. The paint was applied at a film thickness of 2 mm to a silicon-coated Hostaphan®-Foil RNT 36 (Kremer GmbH & Co. KG) and pre-dried in darkness under room condition (23 °C/50%RH) for 1 week. The samples were aged under window glass filtered fluorescence light (True Lite® 5500 K and Philips® UV-20 W/08 F20 T12 BLB generating ≈5,800 lm/m2, 557 mW lm−1/≈3,200 mW/m2) at ≈40 °C, 55%RH and atmospheric oxygen content over a time period of 6 weeks. To investigate the dripping process of oil paint (applied in thick layers), different paint samples were produced in 2003 by H. Schmincke & Co. GmbH & Co. KG, Erkrath (Germany) according to paint formulation of 1994. The paint was applied in variable thickness up to 5 mm on a paint board. The binder of the blue paint (Prussian blue) contains ≈66 % linseed oil, 23 % sunflower oil and 11 % safflower oil. The binder of the light pink paint (titanium dioxide and cadmium pigments) contains ≈13 % linseed oil, ≈70 % sunflower oil and ≈17 % safflower oil. The light pink paint contains Co- and Zr-dryer, whereas the blue paint is free of additives. Pure oil samples used in paint formulation

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