“Starting from a little dot, the crystals grow outward from the centre – growing in the same way as frost on a window in the winter. In fact, it’s the same process – but these crystals grow inside the glaze, so when it cools down they stay locked inside it forever.” The addition of pure oxides creates the kaleidoscopic colour, and in Pekař’s hands, a single ingredient contains many possibilities; nickel oxide, for example, creates a base of warm, rich yellow, and crystals that are electric blue. This double effect is possible thanks to the different structures that are present – “the nickel in the glaze reflects the light differently [depending if it is in the base or in the form of a crystal]. When you think about it, colour is about reflection, it’s not about the surface – this is not a blue or yellow glaze – it’s just that light is made up of different colours, and therefore the different structures produce totally different colours [from the same base ingredient].”