1 Use hydrated lime (a 25 kg bag costs around pounds 5 from builders' merchants). and dye with natural earth pigments such as yellow ochre, red oxide and sienna - pounds 10 a kilo.
2 Lime is caustic, so use gloves. Wear eye protection at all times.
3 Mix the limewash with water and stir in the pigments. If you don't stir them in thoroughly, or you mix two batches differently, the colour shades will vary. Which is exactly what all the fancy modern colour-washing techniques are trying to replicate.
4 Wet the walls, then apply in very thin coats. The first couple of coats, applied at 24 hour intervals, can appear quite disappointing, but lime sets by absorbing carbon dioxide from the atmosphere. It will thicken as it dries.
5 Conservation experts say limewash allows a building to "breathe", that it is unaffected by moisture, and that it acts as a natural antiseptic, discouraging moulds and bacteria.
Earth pigments and traditional limewash can be ordered by post from IJP Building Conservation on 0118-969 6949; there is a 10 per cent discount for Independent on Sunday readers.