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Lecture on the focus of sol-gel coatings

Lecture tip: Lasts longer than it tingles - dishwasher-safe sol-gel coatings for decorations
Anett Kästner, ETC PRODUCTS GmbH, Deggendorf, Germany

 

Abstracts:

Decorated porcelain and glassware are very popular. However, these are often not dishwasher-resistant, as dishwasher resistance of the decorations can only be ensured by deep baking (inglaze) of these into the substrate (porcelain > 1200 °C). However, the range of colors for inglazes is severely limited, because the high temperatures result in a loss of color brilliance and color fastness. In addition, decorations for drinking glasses, for example, cannot be fired deep enough into the glass to ensure dishwasher resistance due to glass deformation at very high temperatures (> 620°C, or even lower depending on the glass thickness). For these reasons, colorful decorations are usually fired under milder conditions. If moderate temperatures are used (porcelain up to approx. 900 °C, glass up to max. 620 °C), scratch resistance can be guaranteed, but dishwasher resistance is no longer a given. Thus, especially with glass decorations, also with high-priced glasses as well as in the gastronomy sector, one often even finds decorations that are declared as hand-washable.

The protection of decor from attack in the dishwasher can be significantly increased by subsequent application of a sol-gel coating containing defined concentrations of zirconium dioxide or titanium dioxide. In addition, the coating can increase the brilliance of the decor by smoothing out roughness. Rinsing machine tests as well as alkali and acid tests showed an increase in optical integrity of at least 300% for glass decorations. For porcelain decorations, an increase in dishwasher resistance of 100 % was obtained by the sol-gel coating.