Budapest Régiségei 18. (1958)

JELENTÉSEK - Duma György: Középkori mázas kerámiák vizsgálata 565-586

QT. DUMA AN ANALYSIS OF GLAZED CERAMICS FROM THE MIDDLE AGES I GLAZED STOVE-TILES FROM THE BEIGN OF LADISLAS V The most important task in connection with the glazed tiles excavated in the Fortress of Buda is the classification of the various types according to dates of origin and workshops. Arranging the types belonging to the 14th and 15th centuries, it has been possible to separate those made during the reign of Ladislas V. The series of tiles displaying identical stylistical characteristics contains pieces of different colours, and they are supposed to have formed the parts of one and the same stove. It was, therefore,necessary to ascertain whether these pieces which, on the strength of a similar appearance, are thought to have belonged to one and the same stove do or do not display — apart from their similar form — such physically or chemically discernible other similarities or discrepancies that would serve to determine their common or different origin. To solve the problem analyses have been made concerning the chemical composition of the basic material of the tiles and their glazing, the changes of colour consequent upon Fig. 1 Green glazing of Sample 1 — 15 x Fig. 2 Crumbled green coating of Sample 1 — 15 x Fig. 3 Surface of Sample 4 with brown glazing. — 25 x Fig. 4 Surface of Sample 26 coated by a glaze of a bluish-green covering effect Fig. 5 Change of colour of the basic substance of Sample 1 induced by reburning Fig. 6 Change of colour of the basic substance of Sample 4 induced by reburning Fig. 7 Change of colour of the basic substance of Sample 26 induced by reburning Fig. 8 Thermal-expansion curve of Sample 1 Fig. 9 Thermal-expansion curve of Sample 4 Fig.-1.0 Thermal-expansion curve of Sample 26 Fig. 11 Thermal-expansion curve of Samples 26 and 26a during heating and cooling a reburning of the basic substance, its behaviour in regard to dilatation, the melting of the glaze, etc. In order to be able to analyze the basic substance of the tiles and their glazed coating, a number of microscopic sections of the tiles had to be made. On the evidence of the physical, chemical and microscopic analyses detailed in the paper it was found that there exists a great similarity and correspondence between the basic substance of the various glazed tile-fragments, while the glazing of the tiles displays not only common features but characteristic divergences as well. The result of the analyses justifies the assumption that all fragments under review had a common origin. It was possible to ascertain that some of the pieces had got later under the surface of the soil than other similar pieces. In this connection, autoclaving performed parallel with dilatometric investigations which demonstrate the natural rehydration of the burnt material in a characteristic manner have proved to be of great value. Fig. 12 Melting of the analyzed glazings at 750° C Fig. 13 Glazed surface of Sample 26 after reburning. —15 x Fig. ]4 Cross-section of Sample 1. — 50 x Fig. 15 Cross-section of Sample la. — 50 x Fig. 16 Cross-section of Sample 26a.

—-50 x Fig. 17 Cross-section of Sample 4. — 50 x Fig. 18 Cross-section of Sample 4a. — 50 X Fig. 19 Cross-section of Sample 46. — 50 x Fig. 20 Cross^section of glaze covering Sample 1, between crossed Niçois. — 120 x Fig. 21 Cross-section of Sample 4 between crossed Mcols. — 120 x Fig. 22. A magnified part of Fig. 21 Fig. 23 Crystalline configuration on the surface of glaze of Sample 4 in incident light CAPTIONS 585