This is a very old technique and derives from a metal fusion technique. It disappeared with the fall of the Roman Empire, but was then taken up in France at the end of the 19th century. Produces bas-relief sculpture forms and fully rounded ones. It is sometimes called Pâte de verre.
The shape prepared in foundry wax is covered with a mould and the wax is removed by heating from a drainage canal and the open space is filled with powdered glass or grains of glass, which takes on the same shape. The wax can even be evaporated. The surfaces can be cold-finished.