Kovács Petronella (szerk.): Isis - Erdélyi magyar restaurátor füzetek 14. (Székelyudvarhely, 2014)
Mester Éva: Nagyméretű üvegfestmények "in situ" vagy műtermi restaurálása
Abstracts Brigitta Mária Kürtösi Medieval mosaic finds from the royal basilica at Székesfehérvár. Researching their history and the way they were made. The subject-matter of the author’s doctoral research builds on investigation of hitherto unpublished Roman and medieval mosaic finds from historical Hungary. In the course of the work, emphasis was placed on examination of mosaic fragments of early medieval origin which have come to light during excavations at the one-time royal basilica at Székesfehérvár. These finds reveal the technical history of the only glass wall mosaic fragments known up until now from the Middle Ages in Hungary. Mosaics are closely connected with their architectural surroundings; in their aesthetics and in their materials they convey information attesting to the characteristic features of a given time and place. Beyond any shadow of doubt, the Székesfehérvár mosaic fragments belonged to a mural work. This meant fundamental differences in comparison with the technique used to make floor mosaics. The material of the mosaic cubes that have come to light is glass. The tesserae are for the most part golden ones, namely pieces where a layer of gold foil has been applied to a cube of transparent glass of a yellowish or pale purplish-brownish hue. The gold foil was traditionally protected by a thin layer of glass (cartellina). If this top protective layer is damaged, then the metal foil becomes more vulnerable. Decorative fragments at the King Stephen the Saint Museum in Székesfehérvár well exemplify the likely technological differences between different kinds of glass mosaic featuring metal foil, as the degree of deterioration varies greatly from one type of cube to another. As well as stray tesserae, a few fragments have survived, of approximately equal thickness (1.8-2.5 cm), bedded in plaster. The colour of the lime-based mortar is white. It does not contain brick rubble; on the other hand, small grains of limestone added as filler can easily be seen. Mortars are very lasting. Marks made by plant matter observable on the reverse side refer to the composition of an initial plaster layer. Regarding its type, a parallel may be drawn with the grounding plasters of the mosaics in St. Mark’s Basilica in Venice and in the Hagia Sophia in Istanbul. In the latter case, a fine bedding layer (intonaco), which held the mosaic cubes, was applied to two layers of coarser grounding (arriccio). During the work, the bedding mortar was applied in smaller amounts, similarly to the giornata in the fresco technique. Mosaic-makers in Byzantium sketched the composition of the mosaic onto the ground plaster, or sometimes directly onto the brick wall. Detailed colour sketches painted in fresco were made for the bedding layers of the mosaics in the Hagia Sophia in Istanbul. Gold and silver cubes were used for backgrounds; sometimes these were mixed with dark purple tesserae. Not only was the effect of gold put onto glass of various hues exploited, but also a role was assigned to colour, painted onto the mortar layer to achieve the utmost colour effect and intensity. On the fragments of the bedding plasters of the mosaic in Székesfehérvár, translucent red and black paint can be observed. There are probably traces of sinopia; the surface was not painted in its entirety. The colour painted on was not identical with the colour of the mosaic cubes set in it. From this, likewise, we may infer the use of an underdrawing. During investigations with a polarising microscope for the making of slides from pieces characteristic of the glass and gold mosaic cubes recovered from the excavations, heterogeneity in the fabric structure of the different types of mosaic glass could be observed: air bubbles and grains of colouring material that had not been mixed in. For the fashioning of the coloured glass tesserae, cast glass, called girdle-cake on account of its shape, was broken into small cubes. This is proved by the rounded-off sides on some of the tesserae; these were from the edges of the ‘girdle-cake’. The (metallic copper) grains of the colouring material (they are less than a micron in size) in the red glass used for mosaic cubes in the royal basilica at Székesfehérvár appear as bands in the base-glass matrix. Quartz and cristobalite employed as materials responsible for opacity are uniformly characteristic of another group of cubes of coloured glass (blue, greyish green, dark purple). The optical characteristics of the tesserae belonging to this type are very similar. The coloration of the blue types results from cobalt content different in proportion from type to type. The use of natural stone, too, was characteristic of the Byzantine tradition, mainly when portraying skin colours. During the investigations into the materials used in the Székesfehérvár mosaics, one type of white stone and one type of red served as samples. The white-coloured stone occurred naturally: it was pure magnesite. Hitherto, there is no example internationally of its use in this way. Soft in colour, magnesite (MgC03) resembles porcelain in appearance. Among the excavation finds were not just a cube-shaped version, but also one formed so as to resemble a disk. The period which followed the foundation of the state favoured ecclesiastical arts in Hungary, and in addition to the royal town, a few more distant, smaller centres, too, began to flourish. In the course of the 11* and 12th 141
