The main raw materials used in the manufacture of nearly all types of glass are silica sand and sodium carbonate. Additionally, lead oxide is used for crystal glass. In its molten state, the glass is formed, either mechanically or by blowing, into the required shape. In many cases, using a diamond wheel, a quite complex pattern may be cut into the surface of the glass after cooling.
The final stage of the manufacturing process is to pass the glass slowly through a bath containing a mixture of hydrofluoric acid and sulphuric acid. Aqueous hydrofluoric acid solutions are the only acids capable of dissolving the raw material, silica, in an acceptable time. It is this final acid treatment which gives crystal glass the sparkling finish for which it is revered throughout the world.