Description

This is a technique used widely in Bohemian Biedermeier glass, English cameo glass, Scandinavian glassworks in the 20th century and Venetian glass in the 19th century.

This technique produces a surface layer of very thin glass.

In the Bohemian, English cameo and Scandinavian traditions (casing or cup-overlay method), a small, open, blown object is shaped, inside of which glass of a different colour is blown until the two walls adhere to each other.

In Scandinavia, another variation is to pour incandescent glass on a blown object of a different colour, which will be the inside one, and made to adhere to the outside wall of the blown object using tools (Graal technique).

In Venice, the blown object at the initial stage is immersed in a crucible of a different colour and then expanded, thereby thinning the wall of the glass. It was used for Roman and also Venetian cameo glass and is still used today to opacify transparent coloured glass on the inside with opaque-white glass.

A particular technique is the one in Venice called 'Suppi' in which a blown object at the initial stage is covered on the outside with a layer of different colour, by pouring another blown object from above, which is then removed from the blow pipe and broken, to obtain a casing. In this case the outside layer is very thin and can appear shaded.