I have just been on a tour of the marvellous Winsor and Newton factory in Harrow. Wearing a white coat and ear protectors, you get to see most of the processes involved in making paint, from the big vats of pigment and the huge rollers that process it until it is the right consistency, to the various methods used to test for viscosity, the machine that extrudes great lengths of solid watercolour. The highlight is the Rose Madder room, where they make pigment the same way they have been using for 200 years – the madder roots are crushed and mixed with some secret substances, left to mature in a jumbo oak barrel, then the mixture is left in a linen hammock for several weeks – the sight of rows of pink tinged hammocks with a very slow quiet dripping beneath them is very beautiful. Finally visitors can try out the paints – transparent yellow and blood-like perylene marroon are my favourites.