Abstract
The article discusses the preliminary results of the analysis and use of the reference pigment collection in order to determine the type of pigment on rock art sites. The collection contains a set of yellow, red, brown and black pigments, mainly of mineral origin. The colour of the paints depends on the specifi c type of pigment used for their preparation, as well as the technology of its preparation e.g. grinding, blending, calcination. The analysis of samples from the collection of pigments with energy-dispersive spectroscopy showed that the red ochres do contain a relatively small amount of iron – less than 12 at%, while the samples from the hematite group, both natural and synthetic, often contain about 40 at%. There is also difference in their colour – when the digital image is transformed from RGB space to HSB, the analysis of the hue channel discovered that at a brightness level less than 30%, the sample can be identifi ed as a hematite, while at a higher brightness it is ochre. Thus, using a digital image only, researchers are able to determine whether an image was made with red ochre or hematite, and if there are several images on the panel they can be divided by their composition, under the condition of the same state of preservation.
The paper shows the relationship between the paint colour and its composition on the example of two sites – the Kapova Cave and the Karakol culture burials. In the Kapova Cave images made both with ochre and hematite were recorded. The example of slabs from the Karakol burials displays that the difference in the colour of paints, determined by comparing the images with the pigment samples from the reference collection, are caused by various sources of raw materials used in decoration of different burials.
Keywords
Rock paintings, pigments, colour, image analysis.
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