| Raw material is mixed with broken re-cycled glass or “cullet” and melted inside a clay refractory pot at temperatures around 1400 C. The clay pot sits inside a furnace and can hold between half and three quarters of a tonne of crystal. Melting can take up to 24 hours and involves a chemical reaction which binds the lead into the silica glass matrix. As well as silica (sand) and lead the raw material contains potash to reduce the melting temperature and refining agents to help clear the gas bubbles formed during melting. It is absolutely vital that the molten mass of crystal is completely homogenous (mixed), as any variation in the state of the crystal will cause faults, imperfections and variations in the end product.
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