Materials of art

"Sigmar Polke uses old and discontinued poisonous pigments, lapis, orpiment, Schweinfurt green. But he does not stop there - he mixes traditional materials with iron, aluminium, potassium, manganese, zinc, barium and adds turpentine, alcohol, methonol, sealing wax and candle smoke to very corrosive lacquers. Many of his paintings are unstable, designed to change in time in unpredictable ways. Some are made with meteorite and tellurium - his work is a physical and chemical exploration of the world of Matter - though the title of the earthiest series - derived from a native American saying - is The Spirits who Lend Help are Invisible."

AS Byatt in the preface to "Strange and Charmed: Science and the contemporary visual arts". Image is Polke's Katastrophentheorie III from here. "The Spirits..." is painted with nickel and artificial resin and various works in the series can be seen here.