This is a thick glass whose decoration consists of several layers of tiny air bubbles arranged uniformly.

To obtain it, the bolo is introduced into a special die lined with metal tips: these leave small spaces on the surface of the molten mass which is then submerged in another layer of molten glass, so that, due to surface tension, they are transformed into tiny air bubbles. 
When this operation is repeated several times, this effect of bubbles one above the other is obtained, giving a sense of lightness to the material.
This process, invented by Flavio Poli at the firm of Seguso Vetri d'Arte , in the mid - 30's, was used to produce very large vases and figures. Many glass factories used this technique without, however, attaining the perfection in execution caught up from Archimede Seguso , that period's master glassblower at the firm of Seguso Vetri d'Arte.