After taking hold of a part of the molten mass (the gob) with a hollow rod, the glassmaker blows into this rod to introduce air into the mass, to form a vacuum. He must regularly heat the mass to keep it in a viscous state.
The glassmaker outlines the shape by making movements with the cane; the object is shaped using various metal or wooden tools, in order to round or stretch the shape. The finished piece is placed in an oven to cool slowly.
For flat glass, the glassmaker longitudinally cuts the cylindrical bubble that has formed in order to open it. When heated, this open cylinder is unrolled to form a flat glass sheet.
The glassmaker can also make a round disc: he blows a bubble and opens it at one end. By a very fast rotating movement of the rod, he flattens this bubble which is transformed into a flat glass disk.
Blowing is still practised by craftsmen today. In industry, the technique of press-moulding has been tried and tested since the 19th century. A glassmaker deposits the mass of liquid glass in a heated mould, while another worker activates a piston to press the glass into this mould.
The glassmaker and jeweller René Lalique (1860-1945) used this process, which he perfected and refined. In Nyon, the architect Gustave Falconnier (1845-1913) developed a blown-moulded glass brick. This invention conquered Europe and the United States, and famous architects - including Auguste Perret, Stephen Sauvestre, and Le Corbusier – used it in their constructions.
Watch the video for an impression of the manufacturing cycle of moulded-pressed glass: https://www.youtube.com/watch?v=77EUuA8qKi0