The actual word sommerso means "submerged" as a description of the glass in the way it is made. It is easy to tell if the glass is sommerso: it will have an edge of clear glass surrounding the colored portion of the class. This bowl starts with the blue glass trail on the outer surface, and as it spirals around the circumference of bowl it becomes completely submerged, until at the top rim it is a blue wisp encased/submerged within the clear.
Does this answer your question, Ivo? It is in the description, and I think the photos are good and show this better than maybe I can describe.