M. Járó - L. Költő szerk.: Archaeometrical research in Hungary (Budapest, 1988)
Analysis - KÖLTŐ László, KIS VARGA Miklós: Composition analyisis of Roman age enamelled bronze objects
KÖLTŐ László*, KIS VARGA Miklós** COMPOSITION ANALYSIS OF ROMAN AGE ENAMELLED BRONZE OBJECTS Abstract — Composition analysis was effected on the enamel inlays of two disk fibulas of one bronze fitting of one clasp and of one capsule. The composition of their basic material was also determined. The composition analysis was effected in November 1984 on the enamel inlays of two disk fibulas (inventory numbers : 55.19.1, 56.1893.6, originating from Csépa and Szőny), of one bronze fitting (56.1893.7, Szőny), of one clasp (105.1891.12, Szőny) and of one capsule (96.1896.1, Sopron, Deák tér) (see Table 1, 1-11), belonging to the collection of the Hungarian National Museum. The composition of their basic material was also determined (Table 2,1-5). (Fig. 1) The analysis was carried out on an X—ray analyser instrument in the Institute of Nuclear Research of the Hungarian Academy of Sciences in Debrecen. The radioactive source was 1—125, with 1200 s measurement time. The elemental composition was determined by the evaluation of the whole spectrum. The enamel analysis was performed without sample extraction on the surface of the enamels, except for the damaged disk fabula with inventory number 56.1893.6. The composition of the basic material was determined on the rear surface of the objects where an approximately 0.5—1 cm 2 surface was cleaned by granule scattering. For cleaning 50-100 £im diameter glass granules were used. The measurement system gave information from an approximately 0.1 mm thick surface layer of the sample. For this reason the results are only qualitative or semiquantitative because the non-uniformly thick enamel layer, which in several cases was damaged, could contain components of the basic metal. Taking into account the above considerations, the following statements can be made : Each enamel contains zinc, which probably caused the darkening of the colours. However, for the fitting with the inventory number 56.893.7 the high zinc content can also partially be assigned to the initially high zinc content of the basic metal (Table 1,4—5 and Table 2, 4). With absolute certainty zinc is a colouring additive for the two fibulas and for the clasp, because in their case zinc is not present in the basic metal. On the basis of their manganese content the red-coloured enamels can be separated into two groups. For the clasp with the inventory number 105.894.12, manganese was found in both analysis points (Table 1,2-3), while there was no manganese in the case of the great disk fibula and the fitting originating from Szőny. The fact that in each case manganese is a component of the enamel is proved by that it was not found in any basic metal, and there was also no manganese in that part of the clasp where only the enamel base remained (Table 1,11). Besides the red-coloured enamels manganese was contained in the millefiori enamel of the smaller disk fibula and in the deep-blue enamel of the capsule. The latter is astonishing while, according to the literature, the manganese oxide additive is used to lighten the colour [ 1 ]. * Directorate of the Museum of the County of Somogy H-7401 Kaposvár, P.O.B. 71 '* Institute of Nuclear Research of the Hungarian Academy of Sciences H-4001 Debrecen P.O.B.51
