This is a system for cold-processing glass surfaces to obtain preset decorations.
It began originally in Bohemia in the XVI century and it was known in Murano a little later on the basis of their models.
Nowadays this engraving is carried out on a lathe using using tools or tip of various types ans sizes. There are two main methods: one uses silicon carbon tips (carborundum) and has relatively short times of operation in relation to the diameter of the tip and to the speed of rotation; the other uses tips of soft metal (copper, for instances) dipped in a grinding powder with different granular grades that, with longer processing times, give more accurate and elegant results.
Murano glass is not the most suitable for operations at the wheel due to its instability and impurity (low content of lead) that determine somewhat irregular markings.
In spite of this, quite outstanding levels of quality have been attained in the past century, quite on a par with the models from Bohemia and Scandinavia as shown by the objects made by Franz Pelzel for S.A.L.I.R. and those by the artist Francesco Andolfato .