The recipe for making glass has changed little for several thousands of years: sand, alkali ashes, and lime from crushed stones are melted together to give a strong, yet fragile material. This molten material can then be manipulated by the glassmaker in a number of ways.This cup and cover, from the late 16th century, was mould blown, this is where a bubble of molten glass is blown into a mould. The mould determines both the shape, and in some cases, the surface decoration. The criss-cross design is called 'vetro a reticello', it is an Italian phrase meaning 'glass with small network'.