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

Hg: mercuric sulphide/cinnabar/ He: hematite / red ochre/ 55 50 45 40 35 30 25 2 V Fig. 3 Diffractogram of red paint sample No. F-256 a, before avid treatment b, after acid treatment Lead(II,III)-oxide may have been present originally in a concentration near the detection limit in the paint sample, moreover its maximum reflections were covered by the reflection of mercuric sulphide. Through the action of hydrochloric acid the pigment was transformed, but based on the transformation product it was possible to conclude its presence in the sample which became richer after the dissolution of calcite. Sample F-530/B (pink) Before acid treatment the pigments providing the colour could not be detected positively by X-ray diffraction owing to the presence of calcite, dolomite, aragonite and a-quartz. The presence of mercuric sulphide and hematite was also assumed (Photo la). After the acid treatment the relative concentration of the pigments increased and, as a result, mercuric sulphide and hematite could be identified (Photo lb).