March 13, 2012, noonView more articles
Last week Hindus all over the world celebrated the festival of Holi, marking the end of winter and the story of the miraculous escape from a fire by Prahalad. Holi is the ‘Festival of Colour’ in the Hindu calendar. Participants cover themselves and others in bursts of vibrant dye that echo the colours of the approaching spring season. The huge festival continues for a week and streets, clothes, faces and animals become multicoloured in the process.
Natural pigments have been used for thousands of years to illuminate glass, colour fabric and even early cosmetics. The green of leaves produced by chlorophyll, different flowers and rare minerals such as ultramarine, were ground, heated and mixed with water to extract colour. Such processes were lengthy and expensive and only the wealthy could afford to wear coloured clothes – often inlaid with gold and other precious metals. ‘Gulaal’ colour is still used in Holi, made from the crushed petals of marigolds. But increasingly dyes are mass produced and synthetic. Synthetic colour is a fairly recent discovery – and was in fact accidental – by a painter in the 1700s Berlin combining different metals and acids. The resulting colour was Prussian blue.
Dyes are not the only substances that use the reactions of metals and pigments to create colour. Fireworks also have metals packed with the gunpowder to produce stunning displays in the sky. The different metals produce different colours when they combust, for example potassium chloride is purple whilst copper chloride produces a blue-green. These reactions are also used in laboratories and industrial settings in ‘flame tests’, where substances are exposed to heat to determine their make up by observing the colours produced.