M. Járó - L. Költő szerk.: Archaeometrical research in Hungary (Budapest, 1988)

Analysis - KRISTON László, JÁRÓ Márta: Impact of acid treatment of pigment samples from wall paintings on the result of paint identification by X-ray diffraction

possible to trace glauconite and calcium-cupric-silicate in the turquoise green sample (Fig. 5a). There were no changes in the structure of the glauconite or that of calcium-cupricsilicate as a result of the acid treatment (Fig. 5b). As an undesirable side effect, not only the proportion of the pigments but also that of the a-quartz grew considerably in the sample. Ca Ca: calcite Q : «-quartz Gl : glauconite /green earth/ E : calcium-cupric-silicate /Egyptian blue/ Ca QGI Gl Q Q Gl Gl Gl 35 30 25 —I— 20 W 2

V Fig. 5 Diffractogram of green paint sample F-1041 a, before acid treatment b, after acid treatment This could be especially disturbing when taking the diffractogram in the DebyeScherrer chamber and therefore it is advisable to remove the quartz grains from the sample at least in the part under the microscope.