Technologiczna analiza późnogotyckich i renesansowych kafli z zamku w Dubiecku

Fragments of selected 10 Gothic and Renaissance tiles coming from the Dubiecko castle area were subjected to technological investigations aimed at achieving the characteristics of material from which the tiles were manufactured and also establishing the approximate features of their make. To determine the raw material of the pottery mass samples were taken for macroscopic examination and the nicol observations including the planimetrie measurements. The above examinations have shown that clay used for the tile manufacture in most cases w'as fairly homogeneous with considerable content of fin e - grained, primary non-plastic components. This could be handled as an indication that, although the production of tiles covered a relatively wide span of t ime, for their manufacture local resources of raw materials were used. As an artificial non-plastic admixture 20 to 27 per cent of sifted quartz grit (no grains of more than 500 u mesh have been found) together with pottery (chamotte) cullet was used; however, no traces of cullet were found in one sample denoted „B-5”. Further, it has been found that some decorative e le ments were formed using the potter’s wheel which the fact has been clearly reflected through the direction of material’s inner pattern in some samples (in particular of that in sample marked A-3). In order to determine the maximum temperature at which the tiles were baked the samples cut out from greater units were subjected to dilatometric measurements allowing to settle their caking point in accordance with the original maximum temperature of product baking. In addition, a thermic differential analysis was applied by means of the curve tracing, recording the changes occurring in substance as result of heat absorbtion or emission (with possible effects only above the temperature to which the sample has originally been heated). The investigations conducted have shown that the temperatures at which the tiles were baked varied from 850°C to 1020°C.