Description
This is a laboratory technique used as early as the Hellenistic and Roman eras, then adopted in Venice in the 15th century.
The gold or silver leaf can be cold-applied to the glass too in the decoration laboratory.
The gold leaf is applied to the glass surface which has been spread with a flux.
Then the decorator takes away some parts using a bone or plastic pointed tool depending on the drawing.
The object is then annealed in a muffle furnace to indelibly fix the gold onto the glass.
In 'early Christian gold bottoms' the decorated glass disc was placed again in a furnace and reheated, then by hot-attaching the bottom of an incandescent blown object, the gold-leaf-engraved decorated surface was protected. The decorated glass disk became the bottom of a blown container.
In the 'Zwischengoldgläser', produced in Germany and Bohemia in the 17th century, the gold or silver leaf, once cold-engraved and applied to a blown object, was protected by placing the object in a wider blown object and the two are cold-sealed along the edge.