Heiremans lumps sommerso and cased glass, as well as glass with inclusions, into a single chapter "Sommerso" in his book Murano Glass, Themes and Variations. He defines sommerso as glass made that has two or more layers made by dipping an object into glass (paraphrased). Thinking of the thinly cased vessels made by Martinuzzi, I have difficult stretching my definition of sommerso to include them. They don't look submerged to me. In fact, they barely look cased. Perhaps Heiremans included cased vessels in this chapter because it is a manner of the degree in thickness of the layers. He did not write of why he had lumped these vessels together.