Similar but never identical Crystals
Clearly, workpieces manufactured according to A) and B) above will have their shape determined by the mould, even though their thickness, weight, and glass separation varies according to the glassworker. Workpieces manufactured according to C) above, on the other hand, are similar but never identical.
A variation can be introduced in techniques B) and C) above in order to obtain the so-called case glass (or verre double, as the French would say), whose manufacturing process is extremely complex and whose secret is jealously guarded by glassworkers. The only thing which can be revealed is that it can be referred to as double work, since it involves heat lamination of two crystal types of different colours.
Glassworkers are organised in groups (called circles) within which each worker has a specific role. The circle leader co-ordinates the whole team who work together in order to manufacture the same workpiece.