Scientists have proved, thanks to experiments performed at the European Synchrotron Radiation Facility (ESRF), that the paintings were made of oil, hundreds of years before the technique was “invented” in Europe.
Via: ScienceDaily Article Link (Apr. 22, 2008) – “The scientists discovered that 12 out of the 50 caves were painted with oil painting technique, using perhaps walnut and poppy seed drying oils.”
“Apart from oil-based paint layers, some of the layers were made of natural resins, proteins, gums, and, in some cases, a resinous, varnish-like layer. Protein-based material can indicate the use of hide glue or egg. Within the various pigments, the scientists found a high use of lead whites.”