CRYSTALLOGRAPHIC STUDIES OF INORGANIC PIGMENTS IN CULTURAL HERITAGE: RED OCHRE AND TERRA VERDE
Featuring Prof. Ulrich Baisch, presenting on behalf of Liana Vella Zarb, Chemistry, Faculty of Science at University of Malta
Inorganic pigments are being used for thousands of years already in arts due to their easy availability and desirable attributes: ochres have been used since prehistoric times to produce cave and rock paintings, and are still used up to this day. Terra Verde (green earth) is a pigment used in decorations and frescos since the first century B.C. Whether these pigments are used in frescos, cave ornaments or paintings, very often, their particular hue, transparency and fading challenge the skills of conservators and restorers. Prof. Liana Vella Zarb will report on the novel approach of Crystal Engineering that was applied. Thus, the effect of different solvents on Venetian red ochre and its solid state behaviour at higher temperatures were investigated and compared with the similar studies on Terra Verde. Powder X-ray diffraction experiments helped identify and quantify the proportions of hematite and goethite in the pigment.