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
4. Testing of samples 4.1. Test samples For the experiments such samples from wall paintings were used conœrning which preliminary tests had already established that they contained the pigments we intended to examine: — red ochre (identified as hematite), — cinnabar (identified as mercuric sulphide), — minium (identified as lead(II,III)-oxide). — yellow ochre (identified as goethite), — green earth (identified as glauconite in most cases), — malachite (identified as malachite), — Egyptian blue (identified as calcium-copper-silicate). In addition, we have analysed mural pigment samples of unknown compositon which were difficult or impossible to identify by X-ray diffraction, where the analyses took place after the interfering white components had been dissolved by acid. The data pertaining to the paint samples chosen for introducing the test results are summarized in Table 2. Table 2 Data of paint samples presenting the test results Test number Colour Place of origin F-256 red Aquincum 2nd—3rd ce. AD. (?) F-530/B pink Aquincum 2nd—3rd ce. A.D. (?) Sz-17 pink Brigetio 2nd c. Ai). Sz-2 yellow Brigetio 2nd c. AD. F-1074 turquoise green Aquincum 2nd—3rd ce. AD. (?) M-2 green Budapest, the church of Elizabethan nuns 18th c. 4.2 Testing conditions The samples were first tested untreated following which they were treated with a 10% solution of hydrochloric acid [4]. In this manner most of the white components (calcium-carbonate, calcium-magnesium-carbonate) may be transformed into compounds that can easily be dissolved. After decomposition the samples were rinsed 1 in distilled water and dried at a temperature of 40°C. Depending on the quantity of the samples at our disposal tests were carried out by diffractometry (Cu radiation, Ni-filter, 40 kV 60 m A 1/4,-0.2,-1/2 slit width, small size sample plate) or by means of the DebyeScherrer chamber (Cu KQ radiation, Ni-filter, 40 kV, 60 mA, 0.5 mm collimator, 3 hr irradiation, 03 mm Lindemann capillary). The most characteristic "d" values of the white components and examined pigments used for identification are contained in Table 3.
