Vysledky prírodovednych analyz Gotckych kamnovych kachlu z Ceského Krumlova

In 1918 a large collection of Gothic stove tiles was found within the area of Cesky Krumlov Castle. 3,868 sherds [sic] have survived till the present day. Analysis of the ceramic material amongst other things was employed to identify the technology of their production and manner of use. We carried out the following analyses on 38 samples altogether: x-ray difraction analysis, optical microscopic analysis of thin sections, water absorption, volume mass and open porosity, temperature expansion analysis, chemical analysis and green glaze analysis. A high proportion of graphite was established (up to 2030% of volume) in the case of the biggest and heaviest tiles (with dimensions of up to 36 x 36 cm). Graphite was intentionally added to the ceramic mixture as a temper due to its attributes (volume stability during changes in temperature). It was partially replaced in the case of the large tiles by the otherwise most common grog-quartz. Tiles with a graphite contact are more resistant during sudden changes in temperature during production and whilst in use. The content of the crystalline phases in the used ceramic mixture reached around 1545% of volume. The firing temperature fluctuated within the span of around 80090 °C. A unilinearly arranged microstructure was established in section mainly in the case of tiles with a cut frontal wall. It was thus possible to demonstrate the production of semi-manufactures--clay slabs, on a potter's wheel. [Publication Abstract]